2013 - kfupm

IV

© Izzat Wajih Kazi

2013

V

Dedicated to

My Professor

Dr.Shaikh Asrof Ali

VI

ACKNOWLEDGEMENT

In the name of Allah the Beneficent, the most merciful, the lord of all universes and

peace be upon the last messenger, Muhammad, his Family and Companions. All praise be

to Allah who give me wisdom, guidance and help that enable me to accomplish this

work.

I would like to express my profound indebtedness and sincere appreciation to my advisor

Professor Shaikh Asrof Ali who has been a constant source of guidance and

encouragement during this research.

I would like to offer my deepest gratitude to Dr. FaizurRahman for his help and training

in performing antiscalants experiments. I am also grateful to the other committee

members Dr. M. Wazeer, Dr. A.Isab and Dr. Nisarullah for their valuable suggestions,

comments and timely advices for improvement of the work.

My gratitude and acknowledgement are due to my parents, both of them died during my

Ph.D., and to my wife and kids for their prayers, patience and moral support that permit

me to indulge my passion for the long task of completing this work.

I am also thankfull to my colleagues and friends who helped and encourage me during

this work. I wish to mention Mr. Monimulmahboob, Dr. Othman, Mr. Shamuddin, Mr.

Hassan Muhannah, Dr. Shemsi, Dr Shahzada, Mr. Kamran and Dr. Shakeel.

VII

I would greatly thankful to Dr. AbdurRahman Al Arfaj (former Director CAPS) and Dr.

Alaaddin Bukhari (Director CEW) for their cooperation and support.

I would like to thanks Mr. M. Arab, Mr. U.Badaruthaman, Mr. Khursheed Alam (late)

Dr. Hakeem Abbas and Dr. Shariq Vohra for their willing cooperation and support during

the experimental study of this work.

I will also acknowledge and thanks to King Abdulaziz City for Science and Technology

(KACST). A minor part of the thesis was supported by KACST through the Science &

Technology Unit at King Fahd University of Petroleum & Minerals (KFUPM) through

project No. 11-ADV2132-04 as part of the National Science, Technology and Innovation

Plan.

Finally I will pay my overwhelming acknowledgement to King Fahd University of

Petroleum & Minerals for extending all facilities and financial assistance and Chairman

Chemistry Department, Dr.Abdullah J. Al-Hamdan for his kindness and cooperation.

VIII

TABLE OF CONTENTS

ACKOWLEDGEMET …………………………………………………………..……….V

TABLE OF CONTENTS…………………………………………………………….....VII

LIST OF FIGURES……………………………………………………………………..XII

LIST OF TABLES……………………………………………………………………...XV

LIST OF SCHEMES………………………………………………………………….XVII

ABSTARCT ENGLISH…………………………………………………………...…XVIII

ABSTARCT ARABIC……………………………………………………………...…..XX

Chapter 1: INTRODUCTION............................................................................................. 1

1.1 Antiscalants .................................................................................................................................... 1

1.2 Aqueous two-Phase Systems (ATPS) ............................................................................................... 2

1.3 Removal of toxic metal ions ............................................................................................................ 2

1.4 Ionic polymers via cyclopolymerization : cationic, anionic, zwitterionic and ampholytic polymers . 3

1.5 Bioseparations in Aqueous Two-Phase Polymer Systems (ATPSs) ................................................. 10

1.6 Scale Formation and its Control in Desalination Plants ................................................................. 13

1.6.1 Scaling in RO plants .................................................................................................................... 14

1.6.2 Chemicals to Control Scale Formation in Desalination Plants .................................................... 15

1.7 OBJECTIVES ................................................................................................................................... 19

8.1 Present state of the problem: ....................................................................................................... 24

Chapter 2: Phosphonobetaine/sulfur dioxide copolymer by Butler’s cyclopolymerization

process............................................................................................................................... 26

IX

2.1 Introduction .................................................................................................................................. 27

2.2 Experimental ................................................................................................................................. 30

2.2.1 Materials .................................................................................................................................... 30

2.2.2 Physical methods ........................................................................................................................ 30

2.2.3 General procedure ..................................................................................................................... 33

2.2.3.1 copolymerization of the monomer 1 with SO2 ................................................................. 33

2.2.3.2 Basification of PPB 2 to APP 3 ........................................................................................... 35

2.2.4 Thermal decomposition, elemental analyses, infrared spectra, 31

P NMR, molecular weights (

) and polydispesity index (PDI) of polymer PPB 2 ........................................................................... 35

2.2.5 Potentiometric titrations ............................................................................................................ 36

2.3 Results and discussion .................................................................................................................. 39

2.3.1 Synthesis and Physical Characterization of the Polymers .......................................................... 39

2.3.2 Infrared and NMR spectra ......................................................................................................... 43

2.3.3 Viscosity measurements ............................................................................................................ 46

2.3.4 Basicity constants ....................................................................................................................... 52

2.4 Conclusions ................................................................................................................................... 56

CHAPTER 3: Synthesis of a Polyaminophosphonate and its Evaluation as an Antiscalant

in Desalination Plant ......................................................................................................... 58

3.1 INTRODUCTION ............................................................................................................................. 59

3.2 EXPERIMENTAL ............................................................................................................................. 63

3.2.1 Physical Methods ....................................................................................................................... 63

3.2.2 Materials .................................................................................................................................... 64

3.2.3 Monomer and polymer synthesis .............................................................................................. 64

3.2.3.1 N,N-Diallyl-3-(diethylphosphonato)propylammonium chloride (2). ................................ 64

3.2.3.2 General Procedure for the polymerization of Cationic Monomer 2. ................................ 65

3.2.3.3 Acidic Hydrolysis of CPE 3 to PZA 4. .................................................................................. 66

3.2.3.4 Basification of PZA 4 to dianionic polyelectrolyte (DAPE) 6. ............................................ 66

3.2.3.5 Basification of PZA 4 to zwitterionic anionic polyelectrolyte (ZAPE) 7. ............................ 67

3.2.3.6 Synthesis and polymerization of zwitterionic monomer 8 and conversion of the resultant

PZ 9 to PZA 4, DAPE 6, ZAPE 7 and anionic polyelectrolyte (APE) 10. ................................................. 67

3.2.4 Evaluation of antiscalant behavior ............................................................................................. 68

3.3 Results and Discussion .................................................................................................................. 69

3.3.1 Synthesis of monomer and polymers ......................................................................................... 69

3.3.2 Infrared and NMR spectra .......................................................................................................... 71

3.3.3 Viscosity measurements ............................................................................................................ 74

3.3.4 Antiscalant Evaluation: .............................................................................................................. 80

3.4 Conclusions ................................................................................................................................... 83

WM

X

CHAPTER 4: Synthesis of a diallylammoniopropanephosphonate-alt-sulfur dioxide

copolymer and its evaluation as an antiscalant in Desalination Plant .............................. 84

4.1 INTRODUCTION ............................................................................................................................. 85

4.2 EXPERIMENTAL ............................................................................................................................. 89

4.2.1 Physical Methods ....................................................................................................................... 89

4.2.2 Materials .................................................................................................................................... 90

4.2.2.1 copolymerization of monomer 1 with SO2 ....................................................................... 90

4.2.2.2 Acidic hydrolysis of CPE 2 to PZA 3 ................................................................................... 93

4.2.2.3 Basification of PZA 3 to dianionic polyelectrolyte (DAPE) 5 ............................................. 93

4.2.2.4 Basification of PZA 3 to ZAPE 6 ......................................................................................... 94

4.2.2.5 Synthesis and polymerization of zwitterionic Monomer 7 and conversion of the resultant

PZ 8 to PZA 3 and DAPE 5 .................................................................................................................... 94

4.2.3 Evaluation of antiscalant behavior ............................................................................................. 95

4.3 RESULTS AND DISCUSSION ............................................................................................................ 96

4.3.1 Synthesis and Physical Characterization of the Polymers .......................................................... 96

4.3.1.1 Solubility ........................................................................................................................... 99

4.3.1.2 Infrared and NMR spectra .............................................................................................. 100

4.3.1.3 Viscosity measurements ................................................................................................. 104

4.3.2 Effectiveness of DAPE 5 as an antiscalant ................................................................................ 111

4.4 Conclusions ................................................................................................................................. 114

Chapter 5: Heavy metal ions extraction using a novel polyphosphonate resin .............. 115

5.1 Introduction ................................................................................................................................ 115

5.2 Experimental ............................................................................................................................... 116

5.2.1 Physical Methods ..................................................................................................................... 116

5.2.2 Materials .................................................................................................................................. 116

5.2.3 Synthesis of monomers ............................................................................................................ 117

5.2.3.1 Hydrolysis of Monomer 1 to Diallylaminopropylphosphonic acid 2 ............................... 117

5.2.4 1,1,4,4-tetraallylpiperazinium dichloride 3 .............................................................................. 117

5.2.5 General Procedure for the Terpolymerization of 2 and 3 with Sulfur Dioxide......................... 118

5.2.5.1 Basification of CPZA 4 to cross-linked dianionic polyelectrolyte (CDAPE) 5 ................... 118

5.2.6 Sample characterization ........................................................................................................... 119

5.2.7 Adsorption experiments ........................................................................................................... 119

5.3 Results and discussion ................................................................................................................ 121

5.3.1 Synthesis of cross-linked polymer 4 and 5 ............................................................................... 121

5.3.2 Adsorption properties of CDAPE 5 ........................................................................................... 124

5.3.3 Adsorption kinetics ................................................................................................................... 125

5.3.4 Effect of initial concentration on the adsorption of copper and lead ions .............................. 130

5.3.5 Effect of pH and temperature on adsorption. .......................................................................... 137

XI

5.3.6 SEM images and EDX ................................................................................................................ 142

5.3.7 Desorption experiment ............................................................................................................ 144

5.4 Conclusion .................................................................................................................................. 144

Chapter 6 : Environmentally benign inhibitors for gypsum scale .................................. 145

6.1 Introduction ................................................................................................................................ 145

6.2 Experimental ............................................................................................................................... 149

6.2.1 Materials .................................................................................................................................. 149

6.2.2 Physical methods ...................................................................................................................... 150

6.2.3 Synthesis of monomers ............................................................................................................ 151

6.2.4 General procedure for polymer Synthesis ............................................................................... 160

6.2.4.1 PSI with Mw 7000 ............................................................................................................ 160

6.2.4.2 PSI with Mw 19000 .......................................................................................................... 160

6.2.4.3 PSI with Mw 100,000 ...................................................................................................... 161

6.2.4.4 PSI derivatives ................................................................................................................. 161

6.2.4.5 Alkaline hydrolysis of PSI/ PSI derivatives ...................................................................... 162

6.2.5 Evaluation of antiscalant behavior ........................................................................................... 164

6.3 Results and discussion ................................................................................................................ 167

6.3.1 Scale inhibition properties of the synthesized polymers ......................................................... 167

6.3.1.1 Effect of PSI- derivative on Induction Period of CaSO4 Scale .......................................... 170

6.3.1.2 w of Sodium Polyaspartate on CaSO4 scale inhibition ................................... 171

6.3.1.3 Effect of Mw of PSI- derivative on CaSO4 scale inhibition ............................................... 172

6.3.1.4 Effect of Sodium Polyaspartate derivatives on CaSO4 inhibition .................................... 173

6.3.1.5 Effect of pendant ratio .................................................................................................... 174

6.3.1.6 Effect of antiscalant dose concentration ........................................................................ 175

6.3.2 EDX and SEM images ................................................................................................................ 177

6.4 Conclusion .................................................................................................................................. 183

CHAPTER 7: Construction of a novel Aqueous two-phase systems with pH-responsive

diallylammoniopropanephosphonate-alt-sulfur dioxide cyclocopolymer and polyethylene

glycol............................................................................................................................... 184

7.1 Introduction ................................................................................................................................ 184

7.1.1 Materials .................................................................................................................................. 186

7.1.2 Phase compositions and phase diagram of PEG –PZA∙SO2 systems ......................................... 188

7.1.2.1 The NMR Method ........................................................................................................... 188

7.1.2.2 Binodals by turbidity method ......................................................................................... 191

7.2 Results and Discussion ................................................................................................................ 195

7.2.1 Solution properties ................................................................................................................... 195

7.2.2 NaCl and NaOH n h bin dal PZA∙SO2 2-PEG ATPS ............................................ 198

XII

7.2.3 The Correlation of the Phase Diagrams Using the Method of Diamond and Hsu .................... 202

7.3 Conclusions ................................................................................................................................. 204

Refereces…………………………………………………….…………………………205

Vitae…………………………………………………...…………………………….....221

XIII

LIST OF FIGURES

Figure 1.1 Various types of ionic polymer ................................................................... 4

Figure 1.2 Phase diagram for ATPS of P−Q−H2O .................................................... 11

Figure 2.1 1H NMR spectrum of monomer 1, PBB 2 and APP 3 in D2O .................. 34

Figure 2.2 13C NMR spectrum of monomer 1, PBB 2 and APP 3 in D2O ............... 38

Figure 2.3 The intrinsic viscosity [g] behavior of PPB 2 (entry 7, Table 1) in the

presence of varying concentrations of added salts at 30 C using an

Ubbelohde viscometer. ............................................................................. 48

Figure 2.4 Reduced viscosity (sp/C) of a 1.0 g/dL solution of polymer PPB 2 (entry

7, Table 1) in salt-free water versus equivalent of added NaOH at 23 C. 51

Figure 2.5 The viscosity behavior of the PPB 2, APP 3 and CPP 4 (obtained via PPB

2 from entry 7, Table 2−1) in salt-free water and 0.1 N NaCl at 30 ᴼC

using an Ubbelohde viscometer ................................................................ 53

Figure 2.6 Plot for the apparent log K1 versus degree of protonation (a) for PPB 2-

APE 3 system (entry 7, Table 2−1) in salt-free water and 0.1 N NaCl. ... 54

Figure 3.1 1H NMR spectrum of monomer 2, CPE 3, DAPE 6 and ZAPE 7 in D2O 71

Figure 3.2 13C NMR spectrum of monomer 2, CPE 3, DAPE 6 and ZAPE 7 in D2O 72

Figure 3.3 The viscosity behavior of CPE 3, DAPE 6, and ZAPE 7 in salt-free water

and 0.1 N NaCl at 30oC using an Ubbelohde Viscometer ...................... 75

Figure 3.4 The viscosity behavior of PZ 9, DAPE 6, and ZAPE 7 in salt-free water

and 0.1 N NaCl at 30oC using an Ubbelohde Viscometer ...................... 78

Figure 3.5 The viscosity behavior of CPE 3, DAPE 6 (via CPE 3), and DAPE 6 (via

PZ 9), 0.1 N NaCl at 30oC using an Ubbelohde Viscometer. ............... 79

Figure 3.6 Precipitation behavior of supersaturated solution of CaSO4 in the presence

(10 ppm) and absence of DAPE 6............................................................. 82

Figure 4.1 DTA-TGA curve of CPE 2 ...................................................................... 99

Figure 4.2 1H NMR spectrum of monomer 1, CPE 2, DAPE 5 and ZAPE 6 in D2O

................................................................................................................. 102

Figure 4.3 13C NMR spectrum of monomer 1, CPE 2, and DAPE 5 in D2O ........... 103

Figure 4.4 The viscosity behavior of CPE 2, DAPE 5, and ZAPE 6 (from entry 7,

Table 4−1) in salt-free water 30oC using an Ubbelohde Viscometer ..... 105

Figure 4.5 The viscosity behavior of PZ 8, DAPE 5 (via PZ 8), and APE 9 (via PZ 8)

in 0.1 N NaCl at 30ᴼC using an Ubbelohde Viscometer. ....................... 108

Figure 4.6 The viscosity behavior of CPE 2, DAPE 5, and ZAPE 6 (from entry 7,

Table 4−1) in the presence of NaCl at 30ᴼC using an Ubbelohde

Viscometer .............................................................................................. 108

Figure 4.7 Precipitation behavior of supersaturated solution of CaSO4 in (a) without

DAPE 5 (b) 10ppm DAPE 5. .................................................................. 113

XIV

Figure 5.1 IR spectra of (a) Cross-linked polyanion 5 loaded with Cu2+

(b) Cross-

linked polyanion 5 loaded with Pb2+

.and (c) Cross-linked polyanion 5 . 124

Figure 5.2 Adsorption kinetic curves of Cu2+

and Pb2+

in 0.1 M solution at their

optimum pH 4 and 5 respectively at a) 295 K b) 308 K c) 323 K. ....... 126

Figure 5.3 Effect of temperature on adsorption capacity of CDAPE 5 .................... 126

Figure 5.4 Lagergren second-order kinetic model for adsorption of Cu2+

and Pb2+

on

CDAPE5 at a) 295 K b) 308 K c) 323 K. .......................................... 128

Figure 5.5 The effect of initial concentration on the adsorption capacity of CAPE 5 at

pH4 for Pb+2

and pH 5 for Cu+2

24 h at 25 ᴼC ....................................... 130

Figure 5.6 Langmuir isotherm of the adsorption of Cu2+

and Pb2+

ions on CAPE 5 131

Figure 5.7 Freundlich isotherm of the adsorption of Cu2+

and Pb2+

ions on CAPE 5

................................................................................................................. 133

Figure 5.8 Temkin isotherm of the adsorption of Cu2+

and Pb2+

ions on CAPE 5 .. 135

Figure 5.9 pH dependence of metal uptake by CDAPE 5 ........................................ 137

Figure 5.10 Arrhenius plot for adsorption of Cu2+

and Pb2+

on CDAPE5 ................. 139

Figure 5.11 Vant-Hoff's plot for adsorption of Cu2+

and Pb2+

on CDAPE 5 ............. 140

Figure 5.12 EDX and SEM images for unloaded and loaded CAPE 5 with Pb2+

and

Cu2+

. ........................................................................................................ 143

Figure 6.1 Precipitation behavior of CaSO4_3CB_40oC in the absence of antiscalant

(blank) ..................................................................................................... 168

Figure 6.2 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm)

antiscalant showing Pendent Effect on Scale Inhibition ......................... 170


antiscalant showing effect of SPSI Mw .................................................. 171


antiscalant showing effect of M w of PSI- derivative on CaSO4 scale

inhibition ................................................................................................. 172


antiscalant showing effect of Sodium Polyaspartate derivatives on CaSO4

inhibition ................................................................................................. 173


antiscalant showing effect of Pendant Ratio ........................................... 174

Figure 6.7 Precipitation behavior of CaSO4_3CB_40oC at 2.5 ppm, 5 ppm and 10

ppm antiscalant concentration a) 10 (DP~70); b) 15 (DP~70); c) 20

(DP~70) and d) Commercial Antiscalant .............................................. 175

Figure 6.8 EDX and SEM images of gypsum at different magnification formed from

3CB CaSO4 after 30 seconds at 40ᴼC while no antiscalant added.( Blank)

................................................................................................................. 178

XV


3CB CaSO4 after 1200 minutes at 40ᴼCwhile using 10 ppm of Sodium

Polyaspartate 10 (DP~70) as antiscalant ................................................. 179


3CB CaSO4 after 3000 minutes at 40ᴼCwhile using 10 ppm of

poly[(azepane-1-yl)aspartamide-ran-sodiumaspartate] 20 (DP~70) as

antiscalant ............................................................................................... 180


3CB CaSO4 after 1800 minutes at 40ᴼCwhile using 10 ppm of

poly[(prrolidine-1-yl)aspartamide-ran-sodiumaspartate] 15 (DP~70) as

antiscalant ............................................................................................... 181


1CB CaCO3 after 50 minutes at 40ᴼC while using 75 ppm of

poly[(azepane-1-yl)aspartamide-ran-sodiumaspartate] 20 (DP~190) as

antiscalant ............................................................................................... 182

Figure 7.1 1H NMR spectra of ((a) Top Phase, system 3: (PZA∙SO2 2, PEG, 0.3N

NaCl, 2.0 equiv. NaOH). b) Bottom phase, system 2: (PZA∙SO2 2, PEG,

0.3N NaCl, 2.0 eqiuv. NaOH)................................................................. 189

Figure 7.2 Phase diagram (■ and □ represent data obtained by respective (NMR and

turbidity method) of PZA.SO2 treated with: a) 1.0 equvi NaOH; b) 1.5

equvi NaOH; c) 2 equiv. NaOH)-PEG-Water (0.3 N NaCl) at 23oC.; d)

effect of different pH on binodal plane. .................................................. 199

Figure 7.3 Effect of added salt on the conformation of polyelectrolytes and

polyzwitterions ........................................................................................ 201

Figure 7.4 Effect of 0.5 ad 1.0 equivalent NaOH on ZAPE 3 ................................ 202

Figure 7.5 Correlation of the Phase diagram of PZA.SO2 (NaOH)-PEO-H2O (NaCl)

systems using the Diamond and Hsu method : using the tie lie data of (a)

Figure1, (b) Figure 2, and (c) Figure 3 ................................................... 203

XVI

LIST OF TABLES

Table 2-1 Cyclocopolymerization of the monomer 1 with sulfur dioxidea ............... 32

Table 2-2 Experimental Details for the Protonation of Monomer 1 (ZH±), and

Polymer PPB 2 (ZH±) at 23oC in Salt-Free Water .................................. 41

Table 2-3 Experimental Details for the Protonation of Monomer 1 (ZH±), and

Polymer PPB 2 (ZH±) at 23 oC in 0.1 M NaC ......................................... 42

Table 2-4 Solubilitya,b

of PPB 2 (entry 7, Table 1) ................................................... 46

Table 2-5 Effect of added salts on the intrinsic viscosity ([a and Huggins constant

(k') of PPB 2 (entry 7, Table 1) ................................................................. 49

Table 3-1 Cyclopolymerization of Cationic Monomer 2a to CPE 3 ......................... 69

Table 3-2 Effect of NaCl on the intrinsic viscosity ([a and Huggins constant (K) of

PZE 8 (entry 2, Table 3−1). ...................................................................... 76

Table 3-3 Concentration of Ca2+

at various times at 50°C in the absencea and

presencea of antiscalant additive DAPE 6 (10 mg/L). .............................. 82

Table 4-1 Cyclocopolymerization of the cationic monomer 1 with sulfur dioxidea to

cationic polyelectrolyte (CPE) 2 ............................................................... 91

Table 4-2 Comparative viscositiesa of CPE 2, DAPE 5, ZAPE 6, PZ 8 and APE 9

................................................................................................................. 106

Table 4-3 Analysis of feed water and reject brine showing major species in RO Plant

at KFUPM, Dhahran. .............................................................................. 106

Table 5-1 Lagergren second–order kinetic model parameters for Cu2+

and Pb2+

adsorption ................................................................................................ 130

Table 5-2 Langmuir Freundlich and Temkin isotherm model constants for Cu2+

and

Pb2+

adsorption ........................................................................................ 136

Table 5-3 The RL values based on the Langmuir isotherm model ......................... 136

Table 5-4 Thermodynamic Data for Pb2+

and Cu2+

adsorption ............................... 139

Table 6-1 Polycondensation of Aspartic Acid ........................................................ 163

Table 6-2 Synthesis of PSI derivatives.................................................................... 163

Table 6-3 Alkali hydrolysis of PSI and PSI derivatives .......................................... 163

Table 6-4 Analysis of feed water and reject brine showing major species in RO Plant

at KFUPM, Dhahran ............................................................................... 165

Table 6-5 A trends of Induction period and inhibition Percentage of the synthesized

polymers for CaSO4 ............................................................................... 169

Table 7-1 Phase Composition of the [POEa + PZA.SO2

b] System at 296 K (1.0 equiv.

NaOH, mNaCl of 0.3 mol•kg−1

) shown in Figure 7.1 ............................ 192




) shown in Figure 7.1 ............................ 193

XVII




) shown in Figure 7.1 ............................ 194

Table 7-4 Values for constant parameter A introduced in equation 5 and equation 6

along with the rmsd of the model from the experimental data of the

partition coefficients ............................................................................... 195

XVIII

LIST OF SCHEMES

Scheme 1-1................................................................................................................... 13

Scheme 1-2................................................................................................................... 16

Scheme 1-3................................................................................................................... 17

Scheme 1-4................................................................................................................... 29

Scheme 1-5................................................................................................................... 30

Scheme 1-6................................................................................................................... 31

Scheme 2-1................................................................................................................... 37

Scheme 2-2................................................................................................................... 46

Scheme 2-3................................................................................................................... 53

Scheme 3-1................................................................................................................... 70

Scheme 3-2................................................................................................................... 81

Scheme 4-1................................................................................................................... 96

Scheme 4-2................................................................................................................. 100

Scheme 5-1................................................................................................................. 130

Scheme 6-1................................................................................................................. 149

Scheme 6-2................................................................................................................. 162

Scheme 6-3………………………………………………………………………….163

Scheme 6-1................................................................................................................. 149

Scheme 6-2................................................................................................................. 162

Scheme 6-3………………………………………………………………………….163

Scheme 6-4................................................................................................................. 164

Scheme 6-5................................................................................................................. 165

Scheme 6-6………………………………………………………………………….166

Scheme 6-7………………………………………………………………………….167

Scheme 7-1………………………………………………………………………….195

Scheme 7-2………………………………………………………………………….204

XIX

ABSTRACT

Full Name Izzat Wajih Kazi

Thesis Title Synthesis and Application of Some Ionic Polymers as Antiscalants

and Components for Aqueous Two-Phase Systems

Major Field CHEMISTRY

Date of Degree May 2013

Ethyl 3-(N,N-diallylammonio)propanephosphonate (I), a zwitterionic monomer and

sulfur dioxide were cyclocopolymerized using azobisisobutyronitrile (AIBN) or

ammonium persulfate (APS) as initiators to afford a pH-responsive

polyphosphonobetaine/SO2 (PPB/SO2) copolymer (II), which on treatment with HCl and

NaOH, gave aqueous solutions of the corresponding cationic polyphosphononic acid

(CPP) and anionic polyphosphonate (APP). The solution properties of the PPB (II)

having two pH-responsive functionalities were investigated in detail by Potentiometric

and Viscometric techniques. Basicity constants of the amine and phosphonate groups in

APP were found to be “apparent” and as such follow the modified Henderson-

Hasselbalch equation.

N,N-Diallyl-3-(diethylphosphonato)propylammonium chloride (IV), a cationic monomer,

was cyclopolymerized in aqueous solutions using t-butylhydroperoxide (TBHP) or APS

as initiators to afford a cationic polyelectrolyte (CPE) (V) having a

(diethylphosphonato)propyl pendent. The CPE on acidic hydrolysis of the diester groups

gave pH-responsive polyzwitterionic acid (PZA) (VI) which on treatment with one and

two equivalents NaOH gave zwitterionic/anionic polyelectrolyte (ZAPE) (VII) and

dianionic polyelectrolyte (DAPE) (VIII), respectively. The solution properties of V-VIII

were investigated in detail by viscometric technique. For the purpose of comparison, the

solution properties of the polymers were correlated to the structurally similar

polyzwitterion (PZ) III having monoethylphosphonate and NH+ groups. When

performance evaluation was carried out for application in Reverse Osmosis (RO) plants,

DAPE at a concentration of 10 ppm in brackish water-feed proved very effective as an

inhibitor against calcium sulfate scale.

For the first time, several new phase diagrams of poly ethyleneglycol (PEG)-VI aqueous

two-phase systems (ATPSs) have been constructed in the presence of varying proportions

of NaOH.

XX

Cationic monomer (IV) was cyclocopolymerized with sulfur dioxide in DMSO using

AIBN as initiator to afford a CPE (IX) having a (diethylphosphonato)propyl pendent.

The CPE IX on acidic hydrolysis of the diester groups gave pH-responsive

polyzwitterionic acid (PZA) (X) which on treatment with one and two equivalents NaOH

gave ZAPE (XI) and DAPE (XII), respectively. The solution properties of the IX-XII

were investigated in detail by viscometric technique. For the purpose of comparison, the

solution properties of the polymers were correlated to the structurally similar

polyzwitterion (PZ) (II). Evaluation of antiscaling properties using concentrated brine

solutions revealed that DAPE at a meager concentration of 10 ppm is very effective in

inhibiting the formation of calcium sulfate scale, and as such can be used effectively as

an antiscalant in Reverse Osmosis plant.

For the first time, several new phase diagrams of poly ethyleneglycol (PEG)-(X) aqueous

two-phase systems (ATPSs) have been constructed in the presence of varying proportions

of NaOH.

A novel cross-linked polyzwitterionic acid (CPZA) (XIII) was synthesized via

cycloterpolymerization of hydrogen 3-(diallylammonio)propylphosphonate (XIV) with

1,1,4,4-tetraallylpiperazinium dichloride (10 mol%) (XVI), a cross-linker,and sulfur

dioxide in the presence of AIBN in DMSO. XIII upon treatment with NaOH, was

converted into a cross-linked anionic polyelectrolyte (CAPE) (XV).The experimental

data for the adsorption of Pb2+

and Cu2+

on CAPE fitted Lagergren second-order kinetic

model and Langmuir as well as Freundlich isotherm models. The adsorption capacity of

Pb2+

was higher than that of Cu2+

while the rate of adsorption was found to be higher for

Cu2+

. The adsorption process was spontaneous and endothermic in nature with negative

and positive values for G and H, respectively. The low activation energies of 12.8 and

17.9 kJ/mol for Cu2+

and Pb2+

, respectively, indicated the adsorption as a favorable

process. The excellent adsorption and very good desorption efficiencies implied the

efficacy of the resin in removing as well as recovering the metal ions from aqueous

solution. An efficient synthetic access to the resin would enable its use in the treatment

of contaminated waste water.

A series of polysuccinimide (XV) of different Mw was synthesized. (XV) under

hydrolysis or aminolysis in the presence of varying proportion of pyrrolidine, piperidine

and azepane were converted into sodium polyaspartate (XVI) and pyrrolidine (XVII) ,

piperidine(XVIII) and azepane-amides(XIX). XVI –XIX were evaluated for their

antiscalaing properties and were found extremely efficient in inhibiting CaSO4 scale

formation.

XXI

ملخص الرسالة

زت وجيه قاضيع :الاسم الكامل

ومكونات أنظمة التناضح العكسيالتوليف وتطبيق بعض البوليمرات أيوني كما :عنوان الرسالة اثنين من المرحلة المائية

الكيمياء :التخصص

٣١٠٢ مايو :تاريخ الدرجة العلمية

-( I)بةوبران ووفرنووات ( ثنرايي للير لموويرو –ن ، ن ) -3تمت البلمرة الللييرل لمراا اي ير

آيسرو بيوتير –بيس –مع ثاوي لكسيد الكبةيت بافتعمال لزو –وهو مووومة ذو شلنل ثناييل اليطب

ثرراوي لكسرريد / ويتةيرر لو بيةفررلنات ايموويرروة كمرراا باايررل لينررتد مررف ذلررو متعرردا النوفررنووو بيترراييف

ومع معالجل هذا البوليمة بلامض الهيردروكلوريو لو . وضل المتجاوب مع ارجل اللم( II)الكبةيت

هيدروكسيد الصوايوة وتجت ملالير ماييرل للمرواا الميابلرل لهرا وهري مراا برامض البرولي ووفرنوويو

ثاوي لكسيد / وقد تمت ارافل بوليمة النوفنووو بيتاييف . الكتيوويل لو ماا البولي ووفنووات ايويوويل

تمتلو وظينتيف متعليتيف بالتناع مع ارجل اللموضل وذلو بافتخداة طةق قياس التي ( II)الكبةيت

وقد وجد لن عوام الياعديل لمجموعات ايمريف والنوفرنووات وري . وةق الجهد وطةق قياس اللزوجل

. هافلبلخ المعدلل -ماا البولي ووفنووات السالبل كاوت ظاهةيل وتتبع معاالل هندرفون

بةوبيرر ( ثنررايي اي ير ووفررنوواتو) -3 –ثنرايي لليرر –لللييررل لمرراا ن ، ن كمرا تمررت البلمرة ا

بيوتير هيردرو –وري مللرول مرايي بافرتعمال ت –وهرو موورومة موجرب -( IV)كلوريد ايموويروة

الرذ ( V)بيةوكسيد لو بيةفلنات ايموويوة كماا باايل لينتد مف ذلو متعردا اللكتةوليرت الموجرب

وبمعالجرل متعردا اللكتةوليرت الموجرب بالتللر . بةوبي ( نايي اي ي ووفنوواتوث)يتضمف مجموعل

المايي اللمضي لمجموعل ثنايي الإفتة وتجت ماا متجاوبل مع ارجل اللموضل هي متعدا اللامض

وبمعالجته بمعاال لو معااليف مف ماا هيدروكسيد الصوايوة وتجت ماا ( VI)ثنايي اليطبيل اييوويل

ومرراا متعرردا اللكتةوليررت ذو اللررلنل ال ناييررل ( VII)ال نررايي اليطررب /ا اللكتةوليررت السررالبمتعررد

بطةييرل ( VIII-V)وقد تمت ارافل تنصيليل لخصايص ملالي المرواا . على التوالي( VIII)السالبل

و ولهرد الميارورل ويرد تمرت ارافرل العيقرل بريف حصرايص ملالير هرذت المتعررداات . قيراس اللزوجرل

التررري تلترررو علرررى ( III( )برررولي زويتةليرررون ) حصرررايص مررراا متعررردا اييوورررات ثناييرررل اليطبيرررل

XXII

وبيف تر تييري ايااء لمراا متعردا اللكتةوليرت ( . NH+)و ( لباا إب ي ووفنووات ) مجموعات

01 لتطبييررات التناضررع العكسرري للمرراء شررديد الملوبررل وبتةكيررز( VIII)ذو اللررلنل ال ناييررل السررالبل

. لجزاء وي المليون ويد تبيف لوها ماا وعالل لمنع تكلس كبةيتات الكالسيوة

IV-ويول مة ت إولاء رفوة بياويل يوظمرل ثناييرل الطرور لمتعردا اي يلريف جييكرول المرايي

. وي وجوا عد مستويات مف هيدروكسيد الصوايوة

–وي اكسريد الكبةيرت بافرتعمال لزو مع ثرا( IV)وقد تمت البلمة الللييل للمووومة الموجب

الرذ يتضرمف ( IX)آيسو بيوتي ويتةي كماا باايل لتنتد مراا متعردا اللكتةوليرت الموجرب –بيس

وبمعالجل هذت المراا بالتللر المرايي اللمضري لمجموعرل . بةوبي ( ثنايي اي ي ووفنوواتو)مجموعل

اللموضرل هري متعردا اللرامض ثنرايي اليطبيرل اييوويرل ثنايي الإفتة وتجت مراا مسرتجيبل مرع ارجرل

(X ) وبمعالجته بمعاال لو معااليف مف مراا هيدروكسريد الصروايوة وتجرت مراا متعردا اللكتةوليرت

علررى ( XII)ومرراا متعرردا اللكتةوليررت ذو اللررلنل ال ناييررل السررالبل ( XI)ال نررايي اليطررب /السررالب

بافررتعمال طررةق قيرراس ( XII-IX)خصررايص ملاليرر المررواا وقررد تمررت ارافررل تنصرريليل ل. التةتيررب

ولهد الميارول ويد تمت ارافل التةابط بيف حصايص ملالي هذت البروليمةات وحصرايص . اللزوجل

وبرريف ترر تييرري ايااء ( . II( )بررولي زويتةليررون)برروليمةات ملررابهل متعرردا اييووررات ثناييررل اليطبيررل

د الملوبررل ويررد تبرريف لوهررا مرراا وعالررل لمنررع تةفرربات كبةيتررات لتطبييررات التناضررع العكسرري لمرراء شرردي

. لجزاء وي المليون 01الكالسيوة عند تةكيز

وري X-ويول مة ت إولاء رفوة بياويل يوظمل ثناييل الطور لمتعدا اي يليف جييكول المرايي

. وجوا عد مستويات مف هيدروكسيد الصوايوة

بافرتعمال البلمرة ( XIII)تعدا اييوورات ثناييرل اليطبيرل ت ليضا تةكيب ماا بامض جديد م

– 0،0،4،4مررع ( XIV)متعرردا النوفررنووات ( ثنررايي للليرر لموويررو) – 3 –الللييررل لمرراا هيرردروجيف

، وهرو مراا ترةابط بينري، و ثنرايي ( XVI%( ) مرول 01) رباعي للي بابةيزينيوة ثنرايي الكلوريرد

بهيدروكسريد ( XIII)وبمعالجرل المراا . آيسرو بيوتبر ويتةير –يس ب –لكسيد الكبةيت وي وجوا لزو

( . XV) الصوايوة تلولت إلى ماا متةابطل بينيل هي متعدا اللكتةوليت السالبل

XXIII

وقررد اشررارت النتررايد التجةيبيررل لمتررزاز ليررون الةنررا وليررون النلرراس علررى مرراا متعرردا

لجةجيف ووموذج حط التلاور ليوجموية مف الدرجرل اللكتةوليت السالبل وبعد ت بيتها على وموذج

ال اويل ووموذج حط التلاور لنةيوودلد لن فعل المترزاز ييرون الةنرا لكبرة منهرا ييرون النلراس

وقرد كاورت عمليرل المترزاز للظيرل . ولكف معدل المتزاز للنلاس اكبة مف معدل المتزاز للةنا

وتلرية طاقرل التنلريط . لرة فرالبل وطاقرل الو رالبي موجبرل ومانل لللرةار كمرا كاورت طاقرل جبرز ال

إلررى لن ( كيلوجررول للجررز ء 0.21)والةنررا ( كيلوجررول للجررز ء 0.21) المنخنضررل للنلرراس

كما لشارت وعاليل عمليل المتزاز وعكسها إلى وعاليل الرةاتند وري . عمليل المتزاز هي عمليل مواتيل

ولهررذا وررمن عمليرل تةكيررب وعالررل لللصرول علررى الررةاتند . المرايي افرتةااا ليررون المعردن مررف المللررول

. فو تزيد اليدر على معالجل الميات الملوثل

بأوزان جزيئيل مختلنرل وري ظرةو ( XV)وقد ت تةكيب فلسلل مف مواا متعدا فكسيناميد

يبريف و تر تلل مرايي لو تللر لمينري ووري وجروا مسرتويات متعردا مرف بيةوليرديف و بايبةيرديف و لز

( XVII)و بايبةيرديف ( XVII)و بيةوليرديف ( XVI)تلويلها إلى ماا متعدا لفبارتيت الصوايوة

لتييي لاايها وي منع التكلس ووجد لن لها وعاليل XIX– XVIوت تييي المواا (. XIX)لميد -و لزيبيف

. عاليل وي منع تكلس كبةيتات الكالسيوة

1

1 CHAPTER 1: INTRODUCTION

1.1 Antiscalants

Demand for antiscalants is growing continuously to control scaling in various industrial

water treatment systems. The development of deposits on heat exchangers (leading to low

system efficiency and heat exchanger failure) and membrane surfaces (resulting in poor

water quality and premature failure) continues to be a limiting factor in the efficient

operation of the desalination plants. To combat scaling problems, scale control additives

are used in desalination plants to reduce or prevent the formation of scale. During the

past two decades, additives (polymeric and non-polymeric) have been successfully used

by the water treatment industry.

Many of the older organic phosphates and phosphonates that were used as scale inhibitors

were quite toxic to the environment. These chemicals are being replaced with less toxic

organic phosphorus compounds. A concept of an all-in-one water treatment chemical

formulation is currently being investigated to prevent corrosion as well as scaling [1]

Using Butler’s cyclopolymerization protocol [2-5]

, we intend to synthesize new pH-

responsive linear ionic polymers having low phosphorous content and test their chelating

ability as antiscalants.

2

1.2 Aqueous two-Phase Systems (ATPS)

The high water content along with low interfacial tension in aqueous two-phase systems

(ATPSs) comprising water-soluble polymers as main components, provides an

environment-friendly compatible avenue for efficient purification as well as separation of

a variety of industrially important labile biomolecules including proteins [6-11]

. The most

commonly used ATPS, based on poly(oxyethylene) (POE) and dextran, has some

limitations due to the dextran being quite expensive and biodegradable [12-15]

.

The

synthesized ionic polymers for the current work will be used as a component in the

construction of aqueous two-phase systems (ATPSs).

1.3 Removal of toxic metal ions

The presence of toxic heavy metal ions, such as Pb2+

, Cu2+

, etc., in natural and waste

water systems is a matter of great concern due to their negative effects on the

environment and human health. By virtue of being nonbiodegradable these toxic

pollutants can accumulate in the human body causing a variety of diseases and disorders

[16-20]. Various techniques, like adsorption, precipitation, dialysis, ion exchange, reverse

osmosis, and extraction, have been developed in the past for the removal of metal

contaminants from water resources. One of the most attractive among these techniques is

presumably the adsorption process due to the availability of different types of low-cost

and environment-friendly adsorbents [21-24]

. Considerable attention has been given to

synthesize chelating agents containing aminomethylphosphonate motif owing to its

extraordinary chelating properties in extracting heavy metal ions from waste water [21]

. In

3

this work, a novel pH-responsive cross-linked polymer bearing aminopropylphosphonate

motifs has been synthesized and tested for its efficiency as an adsorbent for the removal

of heavy metal ions like Pb2+

and Cu2+

ions from aqueous solutions.

1.4 Ionic polymers via cyclopolymerization : cationic, anionic, zwitterionic

and ampholytic polymers

While the polymerization of carbo-, phospho- or sulfo-betaines (zwitterions) (M±) having

charges of both algebraic signs in the same molecular framework lead to polybetaines

(polyzwitterions) [25-26]

, the presence of both M

+ and M

- in the same polymer chain

constitutes a polyampholyte with or without charge symmetry (Scheme 1−1). The

polymer backbones containing cationic and anionic charges are known as cationic and

anionic polyelectrolyte, respectively. Synthetic polyampholytes and polyzwitterions,

whose structure and behavior seem to mimic biopolymers like proteins or DNA that

mediate life processes, have offered many new applications in various fields. Butler’s

cyclopolymerization reaction [2-5]

of zwitterionic diallylammonium monomers or their

copolymerizations with sulfur dioxide have been an attractive method for the synthesis of

polyzwitterions.

Polyampholytes and polyzwitterions, unlike cationic or anionic

polyelectrolytes, exhibit anti-polyelectrolyte behavior [5,27-28]

i.e. enhancement in

viscosity and solubility in the presence of added electrolytes (e.g. NaCl) owing to the

neutralization of the ionically cross-linked network in a collapsed coil conformation of

the polymers.

4

Cyclopolymerization process of n,n-diallyl quaternary ammonium salts has led to the

synthesis of an array of scientifically and technologically important water-soluble

cationic polyelectrolytes. The polymer-architecture having five-membered cyclic units

embedded in the backbone has been recognized as the eighth major structural type of

synthetic polymers. Over 33 million pounds of poly(diallyldimethylammonium chloride)

alone are sold annually for water treatment and another 2 million pounds are used for

personal care formulation [29]

.

Figure ‎1.1 Various types of ionic polymer

+ + + + ++ + +

_ _ _ _ _ _ _ _

± ± ± ± ± ± ± ±

+ ++ +_ _ _ _

+ ++_ _ _ __

Cationic polyelectrolyte

CPE

Anionic polyelectrolyte

APE

Polyzwitterions

PZ

Polyampholyes (With Charge Symmetry)

PA

Polyampholyes (Without Charge Symmetry)

PA

Figure 1.

5

There has been considerable academic as well as industrial interest in the preparation and

properties of water-soluble ionic polymers (Scheme 1−1) [30]

Among a plethora of water-

soluble polymers, cationic quaternary ammonium polyelectrolytes have etched a place of

distinction due owing to their diverse commercial applications [31]

. Pioneering work by

Butler and co-workers [32]

led to the polymerization of a variety of diallyl quaternary

ammonium salts 1 via an intra- and inter-molecular chain propagation (termed

cyclopolymerization) [33-34]

through the five-membered cyclic structure 2 to yield linear

water-soluble polymers 3 (Scheme 1−1).

Scheme ‎1-1

Scheme 1.

NR1 R2

Cl Cl

NR1 R2

I[ ]I

NR1 R2

Cl

n

SO2

Cl

NR1 R2

I SO2

Cl

NR1 R2

I SO2[ ] n

1 2 3

4 5

6

Homo- and co-polymers of diallyl-dialkylammonium salts have found extensive

industrial and commercial applications [35]

. Polydiallyldimethylammonium chloride alone

accounts for over 1000 patents and publications. Quaternary ammonium salts 1-sulfur

dioxide copolymers 5 are also manufactured [36]

commercially and are useful as textile

furnishes, polymer additives, coagulants and thickeners. Further inroad into the water-

soluble polymers has been reported [37-39]

which describes the synthesis of a novel class of

piperazine-based homo- and co-polymers containing quaternary as well as trivalent

nitrogen in the same polymer.

Some of the representative examples of polyzwitterions 6-14 are given in Scheme 1−2.

The cyclopolymerization [5,40-44]

of the monomers 1 gave zwitterionic/or cationic

homocyclopolymers 5 or cyclocopolymers [45-46]

with SO2. Polymer 5 or 5/SO2 which was

then hydrolyzed to their corresponding anionic or zwitterionic polyelectrolytes 11-14.

Polyvinylbetaines show “antipolyelectrolyte behavior”. In contrast to the normal

polyelectrolytes, viscosity of the ampholytic (zwitterionic) polymers is known to increase

with increasing concentration of added salt (like NaCl). Most often polyampholytes are

insoluble in water, however, these polymers show greatly enhanced solubility and

extensive chain expansion upon increasing the salt concentration. Water solubility is

promoted by electrolytes, which disrupt the intra- and inter-molecular ionic or dipolar

network [47-49]

. The increase in viscosity, which is observed in the presence of brine (anti-

polyelectrolyte behavior), make the polyampholytes ideal candidates for high salinity

media and attractive in view of possible applications in enhanced oil recovery [50]

. It is to

7

be noted that the viscosity of polyelectrolytes decreases drastically in presence of salt like

NaCl.

Water-soluble polymers are extremely important for their relevance to theoretical and

applied research[51]

in biotechnology, controlled delivery of active agents and protection

of the environment. Cationic polyelectrolytes have been utilized [52-54]

extensively in

water treatment, papermaking, mineral processing and petroleum recovery. The

flocculation of suspended solids from aqueous solutions represent an important area of

application of polyelectrolytes [55-56]

.

The viscosity of polyampholytes, quite unlike polyelectrolytes, increases in the presence

of added salt (NaCl) and they can also tolerate divalent cations (Ca2+

, Mg2+

, etc) without

being salted out. The commercial utility of polybetaines (polyampholytes) is relatively

unexplored to date. However, their unusual properties make them potential candidates for

brine viscosification, superabsorbency, EOR and drag reduction [35-36]

.

8

Scheme ‎1-2

NR1 R2

1 3

a, R1 = H or Me; R2 = CH2CO2Et; Cl

b, R1 = H or Me; R2 = (CH2)3SO3

n

9

n

N(CH2)3SO3

CHCH2

6

CH2 CHn

C O (CH2)11 N (CH2)3SO3O

CH3

CH3

7

CH2 CHn

C NH (CH2)3 N CH2CO2O

CH3

CH3

8

CH2 Cn

C O (CH2)2 N (CH2)2SO3O

CH3

CH310

CH3

(CH2)3

SO3

N

CHCH2

NR CH2CO2

[ ]

R = H or Me

n

11 12 13 14

N

S

R CH2CO2

O

O

[ ]

R = H or Me

n

NH CH2

CH2

CH2SO3

[ ]n

N

S

H CH2

CH2

CH2SO3

O

O

[ ]n

Scheme 2

NR1 R2

[ ]n

9

A series of new polycarbobetaines from monomers 15-20 is synthesized varying the

length and the position of the hydrophobic side chains, together with the cationic

analogs[57]

. The polycarbobetaines form homogeneous blends with selected inorganic

salts, to provide organic-inorganic hybrid materials (Scheme 1−3).

Scheme ‎1-3

A review [58]

with 200 references on the properties and applications of water-soluble and

water-swelling integral and pendant-type polyampholytes has been published. A review

NCH3(CH2)m (CH2)nCO2Et

m = 0, n = 1m = 0, n = 4m = 0, n = 10m = 4, n = 1m = 10, n = 1

NCH3(CH2)m (CH2)nCO2

Cl

(CH2)n-2

CH3

NCH3 CHCO2Et n = 4

n = 10

Cl

(CH2)n-2

CH3

NCH3 CHCO2

NCH3 (CH2)3SO3

NCH3 CH2 CO2

Scheme 3.

15 16

1718

2019

10

[59] describes the preparation and properties of water-soluble polymers of various types,

including polybetaines, cationic polyelectrolytes and grafted polymers have been

reported.

Interactions between sulfobetaine-based polyzwitterions and polyelectrolytes have been

reported recently [60]

. A review [25,61]

discusses the synthesis, characterization, and

application of polymeric betaines. Catch and release of DNA in coacervate-dispersed gels

has been successfully carried out by the use of polyzwitteions [62]

.

1.5 Bioseparations in Aqueous Two-Phase Polymer Systems (ATPSs)

The use of ionic polymers in aqueous two-phase system (ATPS) is largely unexplored to

date. However, extraction of proteins in two-phase aqueous polymer systems has

received considerable attention. Bioproduct purification is a challenging area, which

requires development of innovative and efficient processes. Aqueous systems provide

friendly environment for the labile protein products [6]

.

Before unfolding our objectives it is worthwhile to shed some light on the historical

background on the use of two-phase aqueous polymer systems in the purification of labile

biochemicals. It is the rule rather than the exception that two water-soluble polymers P

and Q will separate into two phases when mixed in certain composition. One of the layers

is rich in P and the other in Q. A favourable partition coefficient leads to protein

separation and purification in the aqueous two-phase system. In a mixture of two

polymers and water, a two-phase system will arise only when the polymers are present in

11

a certain range of compositions. The following figure represents the constituent

compositions at which phase separation occurs. The concentration (% w/w) of polymer P

plotted as the abscissa and the concentration of polymer Q as the ordinate. The curved

line separating two areas is called a binodal. Compositions represented by points above

the line give rise to phase separation, while mixture represented by points below the line

does not.

Figure ‎1.2 Phase‎diagram‎for‎ATPS‎of‎P−Q−H2O

A composition represented by point A gives a two phase system, while a composition

represented by point D gives a homogeneous solution. A point A represents the

composition of a total system (% w/w P, %w/w Q) and B and C represent the

composition of the bottom and top phases as determined by experiment. Pairs of points

like B and C are called nodes and the line joining them the tie lines. Any points

representing total system on the tie line give rise to phase systems with same phase

compositions for the top and bottom layers, but with different volume ratios of the two

w/w% P

w/w% QA

B

C

. D

Figure 2. Phase duiagram for ATPS of P-Q-H2O

12

phases. The weight ratio bottom phase/top phase is equal to the ratio between the lines

AC and AB. The partitioning of a protein is described by partition coefficient K, which

is defined as K = CT/CB , where CT and CB are equilibrium concentrations of the

partitioned protein in the top and bottom phases, respectively. The protein yields are

determined by the UV spectroscopy at 280 nm absorption.

The aqueous two-phase system has been extensively studied during the recent years [63-69]

The most commonly used polymer systems are based on poly(ethylene glycol) (PEG) and

dextran. In some cases the polymers have been modified with hydrophobic groups and

biospecific ligands for the affinity partitioning of biomolecules[70-72]

. PEG has few

functional groups and it is difficult to attach affinity ligands to it. It would be rewarding

to synthesize and introduce novel polymers, which can form two-phase system and has

many functional groups that can be used for modification. Recently, poly(N-

vinylacetamide) (poly(NVA))-dextran system has been studied [51-55]

for protein

(myoglobin) separation[73]

.

Poly(N-vinylacetamide) has been modified to give

poly(vinylamine) which on subsequent amidation with carboxylic acids afforded

hydrophobically modified polymer that has been studied for protein

[74].

Recently, the use of hydrophobically modified acrylamide-styrene copolymer-PEG in

separation of bovine serum albumin has been demonstrated [75]

; multiblock copolymer

was found to be more effective than random copolymer.

A recent review

[76] describes

the aqueous two-phase system based on ionic liquids as a novel green separation system.

Aqueous two-phase system based on ionic liquids has some unique advantages.

13

Application and mechanism of ionic liquid aqueous two-phase extraction have been

discussed in the review.

In recent years, synthesis of new ionic polymers and their behavior in ATPSs has been

described [77-78]

. The effect of pH and salt concentration on the coexistence curves of

aqueous two-phase systems containing a pH responsive copolymer and poly(ethylene

glycol) has been reported [79]

. Protein Partitioning in ATPSs composed of a pH-

responsive copolymer and poly (ethylene glycol) has been shown to give promising

results [80]

.

Recently, there has been considerable interest in the use of polyethylene glycol (PEG)–

salt based ATPSs in the selective separation of metal ions like Co(II), Fe(III), Au(III), Cd

(II), Hg(II) and nickel(II) among many others [81-85]

. With the discussion in mind, we

intend to synthesise pH-responsive polyphosphonates which would be used for the first

time to construct ATPSs that may find possible applications in bioseparation and

separation of toxic metal ions since polyphosphonates are expected to be effective

chelators.

1.6 Scale Formation and its Control in Desalination Plants

To minimize scaling problems in Multi-Stage-Flash (MSF) or Reverse osmosis (RO)

desalination plants either mineral acid or scale control additives are used. The specific

mechanism of threshold activity of additives used to inhibit scaling is not clearly

understood but it is believed that a common feature of threshold agents is sequestration or

14

the capability of forming stable complexes with polyvalent cations. Threshold treated

solutions are evidently stabilized in some manner involving alteration in crystal

morphology at the time of nucleation and subsequent inhibition in growth rate [86]

.

1.6.1 Scaling in RO plants

In the RO process, the dissolved salts in the feed water are concentrated. If

supersaturation occurs and their solubility limits are exceeded, precipitation or scaling

will occur. Deposition of un-wanted precipitates may result in poor water quality and

premature failures. The commonly encountered deposits in RO system include sulfates,

carbonates, and phosphates of alkaline earth metals, corrosion products, microbiological

mass and suspended matter. The development of deposits on the membrane surfaces

continues to be a limiting factor in the efficient operation of the RO systems. Currently

acceptable methods of preventing scale formation utilize chemicals, which are

generically known as threshold agents. It is well known that the addition of less than

stoichiometric quantities of certain polyphosphates to supersaturated solutions of various

salts would prevent precipitation for substantial periods of time.

15

1.6.2 Chemicals to Control Scale Formation in Desalination Plants

The antiscalants are regularly tested on laboratory bench scale and pilot plants before

using them in actual operational plants [87]

. Development of antiscalant formulations

appears to be an important research area to control scale formation in desalination plants

based on various processes such as Reverse Osmosis, Multi-Stage-Flash and other water

treatment processes like cooling towers, boiler water, oil wells, etc.

The deposits commonly encountered in desalination process include mineral scales (i.e.,

CaCO3, CaSO42H2O, CaSO4½H2O, CaSO4, Mg(OH)2), corrosion products, polymeric

silica and suspended matter. Davey presented an excellent review on the role of additives

in precipitation processes. Logan and Walker [88]

reported the possible mechanism for the

prevention of scale formation. Harris [89]

discussed the effect of various additives in

retarding the precipitation of alkaline scale (e.g. calcium carbonate, magnesium

hydroxide) and sulfate scale in desalination plants.

Dalvi et al [90]

presented the effectiveness of scale control additives polymaleicacid

(PMA) based Belgard EV 2000 and polyphosphonate (PPN) based DSB(M). Among the

two antiscalants, PPN showed slightly better overall efficiency than PMA under similar

bench top experimental conditions. The anionic form of the antiscalants helps prevent

scale formation by sequestering the cations. Typical additives used as antiscalants include

polyphosphates, organophosphonates, poly(acrylic acid), poly(maleic acid), and

copolymers containing a variety of functional groups such as carboxyl, acrylamide,

sulfonic acid, ester, etc.

16

Poly(acrylic acid) and poly(acrylamide) are often used as water-soluble polymers with

anti-scale properties, but they do not exhibit biodegradability [91]

. These polymers pollute

the natural world, with grave environmental consequence. Therefore, there is a demand

for biodegradable water-soluble polymer. Poly(amino acid), which has an amide linkage

as well as a peptide, is completely biodegradable, and as such it has [92-94]

attracted

considerable attention as a candidate for biodegradable, water-soluble polymer for

industrial application. Sodium polyaspartate (SPASP) a poly(amino acid) with carboxylic

acid side chains, exhibit both biodegradability and functionality such as chelating ability

and dispersibility. Sodium polyaspartate has been tested for its calcium ion-chelating

ability [95]

. Inhibition and delay of deposit formation in membrane processes has been

investigated using aspartic acids and their mixtures with surfactants and emulsifiers in the

presence of polyacrylates or phosphonates [96]

.

The polymer based scale inhibitor is selected from polyacrylic acid, acrylic acid

derivative polymer, acrylic acid and acrylic acid derivatives copolymer, polymaleic acid,

maleic acid derivative polymer, maleic acid and maleic acid derivatives copolymer,

polyepoxy succinic acid, polyvinylpyrrolidone, vinyl pyrrolidone derivative polymer,

sulfonated styrene derivatives polymer, polyaspartic acid, aspartic acid derivatives

polymer. In reverse osmosis systems with high silica water, severe and irreversible

membrane scaling can be observed. A study report the results of laboratory experiments

about the influence of Ca2+

- and Mg2+

-ions on the behaviour of supersaturated solutions

of silica in different test waters [97]

. Examples of polymeric silica dispersants are based

on phosphonate, carboxylate and sulfonates [98]

Extraordinary chelating properties of

compounds containing aminomethylphosphonic acid groups in the molecule have

17

attracted considerable attention to synthesize low molecular-weight chelating agents

containing these functional groups that should be able to form polymer-heavy metal ion

complexes from waste water [99-101]

. The formation of soluble Ca

2+ by the polymers will

prevent them from precipitating and thus blocking membranes in reverse osmosis process

in desalination plants

The early work on threshold agents has been extensively reviewed by Elliott [102]

The

mode of action of these threshold agents has not yet been fully explained but would

appear to be due to adsorption of the additive on the growing crystal nuclei which inhibits

growth at the preferred nucleation sites and results in the formation of irregular, distorted

crystals. Leung and Nancollas [103]

reported the results of adsorption of nitrilo-

trimethylene-phosphonic acid on barium sulfate crystals and concluded that only 5%

surface coverage is necessary for complete inhibition of crystal growth. Busch [104]

developed a formulation to control scale build-up on metallic surfaces. Principle

components of the formulation include a chelant, polymeric conditioners, a gluconate, a

triazole and sodium sulfate. Addadi [105]

noticed that the required dosages of these

additives vary from 5 wt.% in solution for the objective of habit modification up to 10

wt.% for total inhibition. In the water treatment industry these additives have been used

successfully to control carbonate as well as sulfate scales.

Reitz [106]

developed a broad-spectrum antiscalant for reverse osmosis desalination plants.

The additive (FLOCON 100) was designed specifically to control calcium sulfate,

calcium carbonate, and strontium sulfate scaling. He presented operating data from

reverse osmosis plant and showed that FLOCON 100 performed better than SHMP. Butt

18

and Rahman [107]

evaluated FLOCON 100 using beaker tests against SHMP. The beaker

experiments indicated that SHMP is not an inferior inhibitor. In fact, its performance was

definitely better than that of FLOCON-100. The reason is probably, HEDP which is

known to be very effective against CaCO3 scale [108-109]

, is not contained in the

FLOCON-100.

Oner et al. [110]

discussed the inhibitory effect of polyelectrolyte architecture on calcium

sulfate dehydrate crystal growth. They investigated the influence of acidic acrylate and

methacrylate polymers by varying polyelectrolyte charge, structure and molecular

weight. They found that acrylates were more effective than equivalent methacrylates and

the higher inhibitory efficiency was attributed to the maximum surface charge density

due to the adsorbed polymer. They determined the effectiveness of the polymers on rate

of precipitation of gypsum by measuring the conductivity of the supersaturated solution

prepared by mixing 0.008M CaCl2 and Na2SO4 solutions at 30oC. Le Gouellec and

Elimelech [111]

studied the effect of hydrodynamics and antiscalant dosage on inhibition of

gypsum scaling in nanofiltration system. They investigated the inhibition effect of

polyacrylic acid (PAA) against gypsum precipitation. They reported that PAA dosage

has strong effect on inhibition of gypsum formation and it does not vary simply with the

number of nuclei formed in a linear manner but, rather prevents the gypsum crystal

growth by other more complex phenomena.

19

1.7 OBJECTIVES

The aim of this proposed research is to synthesize a series of pH-responsive polymers

derived via cyclopolymerization of a new class of specialty diallyl ammonium

monomers. Polyaspartic acid will be modified to obtain new ionic polymers. The pH-

responsive polymers containing trivalent nitrogen, phosphonate, carboxylate

functionalities will be subjected to construction of ATPSs that may have potential

application in the field of bioseparation using, and will be tested as antiscalants in

desalination process.

To achieve this, the proposed study will have the following objectives:

1. To synthesize new diallylammonium monomers 23 and 25 containing

phosphonate pendants (Scheme 1−4).

2. Homopolymerization and copolymerization of the monomers with SO2 to give

a series of homo 26, 28 and co-polymers 27, 29 (Scheme 1−4).

3. The resulting polymers (Schemes 1−4) would be interconverted to

polyzwitterions, zwittterionic/anionic polyelectrolyte, anionic polyelectrolytes

and cationic electrolytes 30-34 (Schemes 1−4). The solution behaviour of the

resulting polymers will be studied in detail.

4. Synthesis of a novel cross-linked resin from hydrolyzed monomer 23 and a

cross-linker, and its use in the removal of toxic metal ions from waste water.

5. To synthesize polyaspartic acid 37 of different molecular masses (Scheme 1−5),

and their elaboration with an aminophosphonate ligand 38 or its corresponding

ester 45 (Scheme 1−6).

6. Construction of ATPSs using some of these polymers (Scheme 1−4 and

1−5) with urethanized polyvinyl alcohol (UPVA) and/or polyethylene

20

glycol. The ATPSs may have potential application in the separation of

some proteins

7. Evaluation (screening) of the synthesized monomers and polymers as

antiscalant to prevent for instance CaCO3 and/or CaSO4 scaling at brine

concentrations and operating conditions prevalent in Reverse Osmosis

desalination plants.

21

Scheme ‎1-4

NH

Scheme 4.

(H2C)3

P(OEt)2O

Br

22 24

21N

(CH2)3

P(OEt)2O

N(CH2)3

P O

OEt

Na+ -O

N(CH2)3

P O

OEt

H

O

H+ exchange resin

NaOH

HCl

N(CH2)3

PO-Na+

O

HO

N(CH2)3

P(OEt)2O

H

Cl

I I

NH (CH2)3

P(OEt)2O

[ ]n

NH

S

O

O

(CH2)3

P(OEt)2O

[ ]n

Cl

Cl

NH (CH2)3

P(OH)2O

Cl

N(CH2)3

P(O-Na+)2O

N(CH2)3

P O

OEt

H

O

[ ]n

N(CH2)3

P O

OEt

H

O

S

O

O

[ ]n

I I

N(CH2)3

P OH

O

HO

N(CH2)3

P O-NaO

OEt

26 27 28 29

30

Cationic

polyelectrolyte

31

Dianionic

polyelectrolyte

32

Anionic

polyelectrolyte

33

Polyzwitterions

34

Zwitterionic/anio nic

polyelectrolyte

2325

SO2SO2

22

Scheme ‎1-5

OH

OH

O

O

H2N H3PO4

NaOH

N

O

O

[]

n

Scheme 5.

NH2

P O

O -

- O

NH2

P O

O -

- O

x equiv

(n-x) equiv

N

O

O

[ ]n-x

[]

x

P O

O -

- O

HN

NH

O

O

35

36

40

37

38

4139

NaOH

1 equiv

[]

n

P O

O -

- O

HN

NH

O

O

[]N

H

O

ONa+ -O

n

38

[]

n-x

[]

n

P O

O -

- O

HN

NH

O

O

NH

O

ONa+ -O

23

Scheme ‎1-6

NH2

P O

O -

- O

38

Br

Br

P(OEt)3

Br

P OEtO

OEt

NaN3

N3

P OEtO

OEt

H2/Pd-C

NH2

P OEtO

OEt

HCl/H2O

NH3+Cl -

P OHO

OH

NaOH

42 43 44

45 46

Scheme 6.

24

1.8 Present state of the problem:

Polyphosphobetaines (containing repeating unit of a dialkylphosphate motif: a derivative

of phosphoric acid, H3PO4), which seem to mimic phospholipid biomembranes, have

offered many new applications [2,112]

. To our knowledge, there are only a few reports [113-

115] that describe the cyclopolymerization of phosphorous acid (H3PO3) derivatives like

diallylaminoalkyl phosphonic acids to polyphosphonobetaines (PPB). Extraordinary

chelating properties of compounds containing aminomethylphosphonic acid groups have

attracted considerable attention to synthesize low molecular-weight chelating agents

containing these functional groups that should be able to form polymer-heavy metal ion

complexes from waste water [104,116−117]

. In pursuit of tailoring pH-responsive polymers,

we describe herein the synthesis of new monomers 23, a cationic phophonium salt, and

25, a zwitterionic phosphonobetaine (Scheme 1−4), and their cyclopolymers (Schemes

1−4). To the best of our knowledge, cyclopolymers of diethyl phosphonate 27 and

monoethyl phosphonate 29 would represent the first examples of this class of ionic

polymers having a three carbon spacer separating the nitrogen and the phosphonate ester

motifs. The synthesis of a series of new pH-responsive polymers would pave the way to

study cationic polyelectrolyte – to – polyzwitterionic – to – anionic polyelectrolyte

transitions involving polymers having identical degree of polymerization.

Poly(acrylic acid) and poly(acrylamide) are often used as water-soluble polymers with

anti-scale properties, but they do not exhibit biodegradability [118]

. These polymers

pollute the natural world, with grave environmental consequence. Therefore there is a

demand for biodegradable water-soluble polymer. Poly(amino acid), which has an amide

25

linkage as well as a peptide, is completely biodegradable [96-98]

, and as such it has

attracted considerable attention as a candidate for biodegradable, water-soluble polymer

for industrial application. Sodium polyaspartate (SPASP) a poly(amino acid) with

carboxylic acid side chains, exhibit both biodegradability and functionality such as

chelating ability and dispersibility.

To the best of our knowledge, utilization of the polymers described in Scheme 1-4 would

indeed be the first attempt to build ATPS using polyphosphonate as a polymer

component. Polyaspartic acid is biodegradable and as such environment friendly.

Development of in-house technology for new additives or antiscalant formulations and

continuous improvement in these formulations will insure reliability against technical

obsolescence and possible threats in case of emergencies. The proposed project is of

strategic importance and would ultimately provide in-house technology for

manufacturing additives that will help owners and operators of desalination plants in

Saudi Arabia and neighboring countries to improve efficiency and economy besides

developing self-reliance.

26

2 CHAPTER 2: PHOSPHONOBETAINE/SULFUR

DIOXIDE COPOLYMER BY BUTLER’S‎

CYCLOPOLYMERIZATION PROCESS

Taken from N.Y. Abu-Thabit, Izzat W. Kazi, Hasan A. Al-Muallem, Shaikh A. Ali,

Phosphonobetaine/sulfur dioxide copolymer by Butler’s cyclopolymerization process,

European Polymer Journal 47 (2011) 1113–1123

ABSTRACT

The zwitterionic monomer, ethyl-3-(N,N-diallylammonio)propanephosphonate and sulfur

dioxide were cyclocopolymerized in DMSO using azobisisobutyronitrile or ammonium

persulfate as initiators to afford a pH-responsive polyphosphonobetaine/SO2 (PPB/SO2)

copolymer. The polymers, on treatment with HCl and NaOH, gave the aqueous solutions

of the corresponding cationic polyphosphononic acid (CPP) and anionic polyphosphonate

(APP). The solution properties of the PPB having two pH-responsive functionalities were

investigated in detail by potentiometric and viscometric techniques. Basicity constants of

the amine and phosphonate groups in APP were found to be “apparent” and as such

follow the modified Henderson-Hasselbalch equation. The incorporation of SO2 moiety

has resulted in the decrease of basicity constant of the nitrogens in the copolymer by

staggering ≥ 2 units of log K in compare to that of the corresponding homopolymer. The

basicity difference is expected to have an effect on the chelating properties of the

polymers. In contrast to many polycarbo and sulfobetaines, the PPB was all found to be

soluble in salt-free water as well as in salt (including Ca2+

and Li+) added solutions. The

PPB demonstrated ‘antipolyelectrolyte’ viscosity behavior and found to have higher

viscosity values in LiCl than in NaCl or NaI.

27

2.1 Introduction

The polymerization of monomeric carbo-, phospho- and sulfo-betaines (zwitterions) (M±)

having charges of both algebraic signs in the same molecular framework lead to the

corresponding polybetaines (polyzwitterions) [25,119-120]

. While biopolymers like proteins

or DNA mediate life processes, commercial polyampholytes (having the presence of both

M+ and M

- in the same polymer chain) and polyzwitterions, whose structure and behavior

seem to mimic biopolymers, have offered many new applications in medicine,

biotechnology, hydrometallurgy and oil industry [107,121]

. The polyzwitterions are

usually derived from free radical polymerization of acrylamide and acrylate-based carbo-

and sulfo-betaine monomers [122]

, while Butler’s cyclopolymerization reaction

[123] of

zwitterionic diallylammonium monomers or their copolymerizations with sulfur dioxide

has been an attractive method for the synthesis of polycarbo- and sulfo-betaines [2-5, 137-

140,124-127]. Most of the known polyphosphobetaines, (containing dialkylphosphate motif: a

derivative of phosphoric acid, H3PO4), are polymeric phospholipid analogues [128]

. To our

knowledge, there are only three reports [108,120-121]

that describe the

homocyclopolymerization of phosphorous acid (H3PO3) derivatives like

diallylaminomethyl- and propyl-phosphonic acids to polyphosponobetaines (PPB). A

novel phosphonic acid monomer containing methacrylate and methylacrylamide motifs

has been prepared for use in dental composites [129]

. Proton conducting ionomers

containing phosphonic acid motif has been used for possible application in polymer

electrolyte fuel cells [130-131]

.

28

Extraordinary chelating properties of compounds containing amine and phosphonate

groups in the molecule have attracted considerable attention to synthesize low molecular-

weight chelating agents that should be able to form polymer-heavy metal ion complexes

from waste water [104,132-133]

. In pursuit of tailoring pH-responsive polymers, we

continue to synthesize the cyclocopolymer 4 of zwitterionic monomer ethyl 3-(N,N-

diallylammonio)propanephosphonate (1) and SO2 (Scheme 2−1). To the best of our

knowledge, phosphonobetaine (PPB)/sulfur dioxide cyclocopolymer would represent the

first example of this class of ionic polymers. The incorporation of electron-withdrawing

SO2 moiety in the polymer backbone is expected to deplete electron density at the

nitrogen, hence decrease its basicity. This would indeed impart remarkable differences in

the chelating properties of (1)/SO2 cyclocopolymer 4 versus the corresponding

homocyclopolymer of (1) [121]

. We intend to measure and compare the apparent basicity

constants of the co- and homo-polymers.

29

Scheme ‎2-1

30

2.2 Experimental

2.2.1 Materials

2,2'-Azobisisobutyronitrile (AIBN) from Fluka Chemie AG (Buchs, Switzerland), was

purified by crystallization from a chloroform-ethanol mixture. Ammonium persulfate

(APS) from BDH Chemical Co. (Poole, UK) was used as received. Ethyl 3-(N,N-

diallylammonio)propanephosphonate was prepared as described [121]

. Dimethylsulfoxide

(DMSO) was dried over calcium hydride overnight and then distilled under reduced

pressure at a boiling point of 64-65C (4 mmHg). All glasswares were cleaned using

deionized water. For dialysis, a Spectra/Por membrane with a molecular weight cut-off

(MWCO) value of 6000-8000 was purchased from Spectrum Laboratories, Inc.

2.2.2 Physical methods

Melting points were recorded in a calibrated Electrothermal-IA9100- Digital Melting

Point Apparatus. Elemental analysis was carried out on a Perkin Elmer Elemental

Analyzer Series 11 Model 2400. IR spectra were recorded on a Perkin Elmer 16F PC

FTIR spectrometer. 1H,

13C and

31P NMR spectra were measured in CDCl3 (using TMS

as internal standard) or D2O at +25 °C (using HOD peak at 4.65 and the 13

C peak of

dioxane at 67.4 ppm as internal standard) on a JEOL LA 500 MHz spectrometer. 31

P

spectra were referenced with 85% H3PO4 in DMSO.

A gentle stream of N2 was passed through distilled deionized water at 90oC for 15 min in

order to remove dissolved gases. This water was used for viscosity measurements in salt-

31

free and salt (NaCl, 99.9% purity) solutions. Viscosity measurements were made by

Ubbelohde viscometer (having Viscometer Constant of 0.005718 cSt/s at all

temperatures) using CO2-free water under N2 in order to avoid CO2 absorption that may

affect the viscosity data. Molecular weights of some synthesized polymers were

determined by GPC analysis using Viscotek GPCmax VE 2001. The system was

calibrated with nine polyethylene oxide monodispersed standards at 30°C using two

Viscotek columns G5000 and G6000 in series.

32

Table ‎2-1 Cyclocopolymerization of the monomer 1 with sulfur dioxidea

Entry

No.

Initiator

(mg)

Temp

(°C)

Time

(h)

Yield

(%)

Intrinsic Viscosityb

(dl g-1

)

Salt-free 0.1 N NaCl

WM

(PDI)d

1

AIBN (100) 65 24 trace

2

AIBN (75) 65 24 trace

3

AIBN (75) 63 24 27 0.0205 0.0243

5 AIBN (75) 57 48 62 0.0791 0.0957

6 AIBN (60) 57 48 42 0.0225

0.0268

4

AIBN (48) 57 48 50 0.0785 0.0973 67,300 2.3

7 AIBN (100) 50 48 66 0.0802 0.0992 72,100 2.2

8 AIBN (75) 45 48 trace

9 APS (130)

45 3 54 0.0761 0.0906 67,100 2.3

10 APS (100)

45 48 56 0.0733 0.0916

11 APS (60)

45 48 19 0.0801 0.0977

aPolymerization reactions were carried out using 15 mmol each of the monomer and SO2

in DMSO (3.75 g) in the presence of azobisisobutyronitrile (AIBN) or ammonium

persulfate (APS). bViscosity of 1-0.25 % polymer solution in salt-free and 0.1 N NaCl at 30

oC was

measured with a Ubbelohde Viscometer (K=0.005718). cPolydispersity Index.

33

2.2.3 General procedure

2.2.3.1 copolymerization of the monomer 1 with SO2

All the polymerizations were carried out using conditions as described in the Table 2−1.

In a typical experiment, SO2 (15 mmol) was absorbed in a solution of the monomer 1 (15

mmol) in DMSO (3.75 g). The required amount of the initiator AIBN or APS (as listed in

Table 2−1) was then added under N2 and the closed flask was stirred using a magnetic

stir-bar at the specified temperature and for duration as listed. The polymer was dissolved

in water and dialyzed against deionized water for 48 h. The resulting solution of PBB 2

was freeze dried to obtain the white polymer, which was stored in a desiccator.

34

Figure ‎2.1 1H NMR spectrum of monomer 1, PBB 2 and APP 3 in D2O

35

2.2.3.2 Basification of PPB 2 to APP 3

To a solution of PPB 2 (entry 7, Table 1) (0.623 g, 2 mmol) in water (7 cm3) in a

dialysis bag was added a solution of NaOH (0.240 g, 6 mmol) in water (7 cm3). The

solution in the dialysis bag was briefly shaken and then dialyzed against distilled

deionized water for 24 h. The resulting solution of APE 3 was freeze dried to obtain the

white polymer (0.587 g, 88%), which was stored in a desiccator. The onset of thermal

decomposition (Closed capillary) 245-255oC (decomposed, turned black); (Found: C,

39.3; H, 6.5; N, 4.1; S, 9.4. C11H21NNaO5PS requires C, 39.64; H, 6.35; N, 4.20; S, 9.62

%).max (KBr) 3423, 2978, 2921, 1647, 1458, 1417, 1307, 1173, 1129, 1039, 945, and

791 cm-1

. P (202 MHz, D2O): 25.45. 1H and

13C NMR spectra are shown in Figures 2−1

and 2−2, respectively.

2.2.4 Thermal decomposition, elemental analyses, infrared spectra, 31

P NMR,

molecular weights ( ) and polydispesity index (PDI) of polymer PPB 2

The onset of thermal decomposition (Closed capillary) 240-250oC (decomposed, turned

black); (Found: C, 42.2; H, 7.2; N, 4.40; S, 10.0. C11H22NO5PS requires C, 42.44; H,

7.12; N, 4.50; S, 10.30 %); max (KBr) 3361, 2937, 1467, 1296, 1158, 1125, 1026, 941,

and 778 cm-1

. P (202 MHz, D2O): 25.79 and a minor (5%) signal at 25.03 ppm.

For the determination of molecular weights, the polymer PPB 2 was analyzed using an

aqueous solution of 0.1 N NaNO3 as the eluant. Refractive Index and viscometer

WM

36

detectors were used to detect polymers. The molecular weight ( ) and PDI of some of

the polymers are given in Table 2−1.

2.2.5 Potentiometric titrations

The potentiometric titrations were carried out at 23oC as described elsewhere,

[24]. For

each titration, 200 cm3 of salt-free or 0.1 N NaCl solution containing a weighed amount

(usually around 0.15-0.27 mmol of the monomer or repeating unit) of PB 1 or PPB 2 was

used. The solution was titrated at 23 oC with ~0.1 M HCl (or ~0.1 M NaOH) delivered

by a buret under N2. After each addition of the titrant (in the range 0.10 – 0.25 cm3) the

solution was stirred briefly, using a magnetic stir bar, under N2. The pH of the solution

was recorded using a Corning pH Meter 220.

The protonation constant of the amine nitrogen, Log K1, is calculated at each pH value

by the well-known Henderson-Hasselbalch Equation 1 (Scheme 2−2) where degree of

protonation () is the ratio [ZH±]eq/[Z]o. For the titration with NaOH, the [Z]o is the

initial analytical concentration of the monomeric units in the PPB 1 and [ZH±]eq is the

concentration of the protonated species at the equilibrium given by [ZH±]eq = [Z]o - COH

- -

[H+] + [OH

-], where COH

- is the concentration of the added NaOH; [H

+] and [OH

-] at

equilibrium were calculated from the pH value [25,135]

.

The typical electrolytes having apparent basicity constants could be described by the

Equation 2 (Scheme 1−2) where log Ko = pH at = 0.5 and n = 1 in the case of sharp

basicity constants. The linear regression fit of pH vs. log [(1-)] gave log Ko and ‘n’

WM

37

as the intercept and slope, respectively. Simultaneous protonation of the two basic sites

is least likely since the basicity constant for the PO(OEt)O- group is less than that of the

amine group by at least 7 orders of magnitude. The second step protonation constant (log

K2) involving the PO(OEt)O- is calculated by titration of the PB 1 or the monomeric units

in the PPB 2 with HCl. In this case, represents the ratio [ZH2+]eq/[Z]o whereby [ZH2

+]eq

equals CH+ - [H

+] + [OH

-] and CH

+ is the concentration of the added HCl.

The experimental details of the potentiometric titrations are summarized in Tables 2 and

3. Inserting the value of pH from Equation 2 into Equation 1 leads to modified

Henderson-Hasselbalch equation (Eq. 3)[136-137]

(Scheme 1−2) where (n – 1) gives a

measure of the deviation of the studied polymers from the behavior of small molecules

showing sharp basicity constants (for molecules having sharp basicity constants, n

becomes 1).

38

Figure ‎2.2 13C NMR spectrum of monomer 1, PBB 2 and APP 3 in D2O

Scheme ‎2-2

39

2.3 Results and discussion

2.3.1 Synthesis and Physical Characterization of the Polymers

The results of the polymerization under various conditions are given in Table 2−1. As

evident from the Table, decreasing the temperature led to an increase in the yield of the

polymer 2. While no polymerization occurred at 65oC (entries 1 and 2), the highest yield

and viscosity was obtained at 50oC (entry 7). The results thus indicate the presence of a

ceiling temperature for the polymerization. Changing the initiator from AIBN to

ammonium persulfate (APS) (entries 9-11) did not improve the yield. The low yield and

molecular weight as indicated by lower intrinsic viscosity values (Table 2−1) could be a

result of chain transfer between polymer and monomer through the alkoxy group attached

to the phosphorous atom [138]

.

PPB 2 was found to be stable up to 240C and thereafter decomposes as result of

elimination of SO2. The PPB 2 was found to be readily soluble in water as well as in

protic solvents having higher dielectric constants (Table 2−4); hydrogen bonding with the

protic solvents is responsible for the solubility behavior. Nonprotic solvents like DMF

and DMSO having high dielectric constants failed to dissolve the polymer.

Polyzwitterions are in general expected to be insoluble in water. However, there are quite

a few exceptions. A considerable number of polycarbo- and sulfobetaine are reported to

be soluble in salt-free as well as salt (NaCl) added solutions [29,139]

. It is reported that

carbobetaines having carboxyl pKa values of ≤ 2.0 and > 2 are found to be insoluble and

soluble, respectively, in salt-free water [44,128,140]

. It is explained that the negative charges

40

in carbobetaines, having apparent carboxyl pKa values >2.0, are expected to be less

dispersed, hence more hydrated. The higher degree of hydration thus led to exhibit

weaker Coulombic interactions with the cationic charges thereby resulting in their

solubility in salt-free water. Steric encumbrance around the charges also prevents

effective intra- or intermolecular Coulombic interactions, thereby leading to the solubility

of polyzwitterions in salt-free water [112,142]

,. It is worth mentioning that the temperature

and molecular weight also may dictate the solubility behavior of polybetaines [143]

. Since

the phosphonate [O=P(OEt)O-] pKa in PPB 2 is determined to be > 2, the

polyphosphobetaine is expected to be soluble in salt-free as well as salt-added water (vide

infra).

41

Table ‎2-2 Experimental Details for the Protonation of Monomer 1 (ZH±), and Polymer PPB 2 (ZH±) at

23oC in Salt-Free Water

run ZH± or Z

-(mmol) CT

a

(mol dm-3

) range pHrange Points

b Log Ki

o c ni

c R

2,

d

Polymers PPB 2 ( ZH±) in salt-free water

1 0.1783 (ZH±)

0.1001 0.780.19 7.10-10.36 16 8.57 2.80 0.9975

2 0.2104 (ZH±)

0.1001 0.760.18 7.04-10.45 18 8.54 2.78 0.9953

3 0.2457 (ZH±)

0.1001 0.780.22 7.06-10.15 19 8.64 2.82 0.9978

Average 8.58 (5) 2.80 (2)

Log K1 e = 8.58 + 1.80 log [(1-)/]; For the reaction: Z

- + H

+ ZH

±

monomer 1 ( ZH±) in salt-free water

Log K1 e = 8.99; For the reaction: Z

- + H

+ ZH

±

Polymers PPB 2 ( ZH±) in salt-free water

1 0.2524 ( ZH±) +0.09930 0.180.47 2.982.56 21 2.53 0.68 0.9913

2 0.1908 ( ZH±) +0.09930 0.190.51 2.98-2.54 18 2.57 0.66 0.9922

3 0.1626 ( ZH±) +0.09930 0.14 0.42 3.08 15 2.51 0.74 0.9978

Average 2.54 (3) 0.69 (4)

Log K2 e = 2.54 - 0.46 log [(1-)/] For the reaction: ZH

± + H

+ ZH2

+

Monomer 1 ( ZH±) in salt-free water

Log K2 e = 2.39; For the reaction: ZH

± + H

+ ZH2

+

aTitrant concentration (negative and positive values indicate titrations with NaOH and HCl, respectively).

bNumber

of data points from titration curve.

cValues in the parentheses are standard deviations in the last digit.

dR = Correlation coefficient.

elog Ki = log Ki

o + (n – 1) log [(1 - .

42

Table ‎2-3 Experimental Details for the Protonation of Monomer 1 (ZH±), and Polymer PPB 2 (ZH±) at

23 oC in 0.1 M NaC

run ZH

±

-(mmol)

CT a

(mol dm-3

) range pHrange Points

b Log Ki

o c ni

c R

2,

d

Polymers PPB 2 ( ZH±) in 0.1 N NaCl

1 0.1905 (ZH±)

0.1001 0.830.14 6.189.01 15 7.63 1.94 0.9937

2 0.2361 (ZH±)

0.1001 0.790.18 6.528.85 15 7.66 1.91 0.9973

3 0.2923 (ZH±)

0.1001 0.790.15 6.519.02 20 7.65 1.87 0.9988

Average 7.65 (2)

1.91 (4)

Log K1 e = 7.65 + 0.91 log [(1-)/] For the reaction: Z

- + H

+ ZH±

Monomer 1 ( ZH±) in 0.1 N NaCl

Log K1 e = 8.74 ; For the reaction: Z

- + H

+ ZH±

Polymers PPB 2 ( ZH±) in 0.1 N NaCl

1 0.3244 ( ZH±) 0.0993 0.12-0.57 3.31-2.66 22 2.75 0.66 0.9946

2 0.2634 ( ZH±) 0.0993 0.14-0.63 3.30-2.68 22 2.78 0.63 0.9893

3 0.1792 ( ZH±) 0.0993 0.13-0.48 3.35-2.73 20 2.74 0.71 0.9914

Average 2.76 (2) 0.67 (4)

Log K2 e = 2.76 - 0.33 log [(1-)/] For the reaction: ZH

± + H

+ ZH2

+

Monomer 1 ( ZH±) in 0.1 N NaCl

Log K2 e = 2.52 For the reaction: ZH

± + H

+ ZH2

+

aTitrant concentration (negative and positive values indicate titrations with NaOH and HCl, respectively).

bNumber of data points from titration curve.

cValues in the parentheses are standard deviations in the last digit.

dR = Correlation coefficient.

elog Ki = log Ki

o + (n – 1) log [(1 - .

43

2.3.2 Infrared and NMR spectra

The strong absorptions at 1158 and 1026 cm-1

in the IR spectrum of PPB 2 were

attributed to the stretching frequency of P=O and P-O-C, respectively. 1H and

13C NMR

spectra of monomer PB 1 and its polymers PPB 2 and APP 3 are displayed in Figures

2−2 and 2−3, respectively. The proton signals of 2 are shifted downwards in comparison

with that of 3 as a result of increased electronegativity of the positive nitrogen in the

former. The absence of any residual alkene proton or carbon signal in the spectra also

suggested the chain transfer process [144]

for the termination reaction. Because of the

width and overlap of the peaks in the spectrum, the size of the ring cannot be determined

from the 1H NMR spectrum.

The assignments of the 13

C peaks are based on earlier works, which confirmed the

formation of kinetically favored five-membered ring structure [135,145-148]

,. The

substituents at the C-b of the PPB 2 can either be in the symmetrical cis (major) or

unsymmetrical trans (minor) dispositions (Scheme 2−1).The cis/trans ratio of 75/25 was

determined by integration of the relevant peaks in the 13

C spectrum. The ratio was found

to be similar to that observed for the related polymers derived from cyclopolymerization

of quaternary diallyl ammonium ammonium salts.[4,135,149]

The cis substituents at C-b of

the cis form can exist in two structural forms; the (CH2)3PO(OEt) group can either be

trans- or cis- oriented with respect to the cis substituents at C-b (Scheme 2−3). The

presence of the two major cis forms of 2 in unequal proportions thus leads to the unequal

splitting of the signals (acis, bcis, Fig. 2−2). The C-a as well as C-b signals of 2 also show

two weak lines of equal intensity in each case for the minor trans (atran, btrans, Fig. 2)

44

which can exist solely in one form in which case C-a and C-a' or C-b and C-b' becomes

magnetically and chemically non equivalent. However, it is interesting to note that the

polymer 3 have trivalent nitrogen that undergoes fast nitrogen lone pair inversion in the

NMR time scale, and as such the -(CH2)3PO(OEt) group loses its stereochemical

integrity, and the splitting of the carbon signals in the cis or trans forms is not observed

(Fig. 2−2, Scheme 2−3). The correctness of the assignment of carbon signals was

confirmed by DEPT experiment using polymer 3 at 135°; the carbon signals bcis and btrans

were ascertained to be that of the methine (CH) carbons. The DEPT experiment thus

ruled out the possible existence of the highly unsymmetrical six-membered rings in

structure A as the predominant repeating unit (Scheme 2−3). In such a scenario, the

methine carbons C-b and C-e would have appeared at ~ 35 and ~65 ppm, respectively

[41]. The signal-to-noise ratio achieved in the

13C spectra of

poly(diallyldimethylammonium chloride) set an upper limit of 2-3% for possible

existence of any six-memberd ring piperidine structure [37]

. The report [150]

on the

structure of cyclocoplymers of dialkyldiallyl ammonium salts with SO2 have established

the existence of predominant, if not exclusive, five-membered pyrrolidine rings.

Detection of structure A and its quantification are further complicated by the possibility

of cis- and trans- orientations of the substituents at C-b and C-e. DEPT experiment of 3

revealed the presence of a methylene and a methine (CH) carbon at 40.1 and 50.8 ppm,

respectively, which could presumably be assigned to the C-b and C-a of the piperidine

ring in structure A. The six-membered ring structure may thus be present to the extent of

3% as approximated by integration.

45

Scheme ‎2-3

46

Table ‎2-4 Solubilitya,b of PPB 2 (entry 7, Table 1)

2.3.3 Viscosity measurements

Viscosity data were evaluated by the Huggins equation: sp/C = [+ k [C. Unlike

in the case of a polyelectrolyte, the Huggins viscosity plot for PPB 2 in the absence or

presence of added salt (NaCl) remains linear. The intrinsic viscosity, slope and Huggins

constant are included in Tables 1 and 5. “Anti-polyelectrolyte” behavior of the PPB 2 is

manifested as a result of increased intrinsic viscosity in the presence of an added salt

(Figure 3, Table 5). Note that for a common Na+ cation, the intrinsic viscosity increases

as the anion is changed from Cl- to I

- in the presence of 0.1 N salts (Figure 2−3, Table

Solvent Dielectric constant, Solubility

Formamide 111.0 +

Water 78.4 +

Formic acid 58.5 +

DMSO 47

Ehylene glycol 37.3

DMF 37

Methanol 32.7

Diethyleneglycol 31.7

Ethanol 24.5

Acetone 21

Acetic acid 6.1 a2%(w/w) of polymer solution was made after heating the mixture at 70C for 1

h and then cooling to 23C. b‘+’ indicates soluble; ‘-’ indicates insoluble.

47

2−5). This is expected since the iodide anion is more polarizable (soft), hence it is

particularly effective in neutralizing the cationic charges on the polymer backbone. A

decrease in the value for the Huggins constant k in the presence of NaI in comparison to

NaCl may be associated with an increased polymer-solvent interaction. However, for a

common anion Cl-, viscosity increases as the cation is changed from Na

+ to Li

+. The

hydration shell of Li+, having a larger charge/radius ratio, is larger than that of Na

+, and

as such makes it less effective than Na+ in shielding the phosphonate anions. The

increased repulsions among the more exposed anionic pendants in the presence of LiCl

lead to a higher viscosity value owing to an increase in the hydrodynamic volume.

Contrary to earlier reports on polycarbo- and sulfobetaines [112,144,146]

. it is interesting to

note that the viscosity values were found to be higher in the presence of LiCl than NaCl

or even NaI (Figure 2−3). At higher salt concentrations, the increase in [] either tends to

level off or decreases a little (in the presence of NaCl). Upon completion of the site and

atmospheric binding [151]

of the cationic charges on the nitrogens by Cl-, the exposed

anionic phosphonate pendents in sea of Na+ ions are also expected to be shielded to a

certain degree, thereby leading to a decrease in [] values at the higher end of NaCl

concentrations. The divalent cation Ca2+

, which is usually known to precipitate anionic

polyelectrolytes from aqueous solution even at low concentrations, did not precipitate the

PPB 2.

48

Figure ‎2.3 The intrinsic viscosity [g] behavior of PPB 2 (entry 7, Table 1) in the presence of varying

concentrations of added salts at 30 C using an Ubbelohde viscometer.

.

49

Table ‎2-5 Effect of added salts on the intrinsic viscosity ([a and Huggins constant (k') of PPB 2 (entry 7,

Table 1)

Solvent Slope [ k

Salt-free H2O 0.0175 0.0802 2.72

0.1 N NaCl 0.0052 0.0992 0.528

0.5 N NaCl 0.0136 0.106 1.21

1.0 N NaCl 0.0119 0.0985 1.22

0.1 N NaI 0.0046 0.107 0.402

0.5 N NaI 0.0084 0.0984 0.867

1.0 N NaI 0.0158 0.0975 1.66

0.1 N LiCl 0.0215 0.108 1.84

0.5 N LiCl 0.0146 0.113 1.14

1.0 N LiCl 0.0069 0.114 0.531

0.1 N CaCl2 0.0096 0.103 0.905

0.1 N HCl 0.0050 0.0907 0.607

0.1 N CsCl 0.0156 0.103 1.47

aViscosity of 1-0. 25 % salt-added polymer solution at 30

oC was measured with a

Ubbelohde Viscometer (K=0.005718).

50

The changes in reduced viscosities of a 1.0 g/dL solution of the polymer (entry 7, Table

2−1) in salt-free water at 30°C in the presence various amounts of HCl and NaOH

demonstrates the pH-responsiveness of PPB 2 as displayed in Figure 2−4. Reduced

viscosity does not change with the addition of HCl; the amount of added HCl is not

sufficient enough to shift the equilibrium (PBB) 2 ⇌ (CPP) 4 towards the CPP. The

presence of increasing proportion of the protonated form 4 is expected to increase the

viscosity as a result of increased repulsions among the unshielded cationic charges on the

nitrogens. A steep increase in the viscosity values is observed on the addition of NaOH

which changes the polymer PPB 2 to the zwitterionic/anionic polymer (PPB/APP) 5 and

finally to APP 3. The anionic motifs in 5 provoke an extension of the polymer backbone

owing to the increased repulsion among negative charges. A decrease in the viscosity

upon addition of greater than 1 equivalent of NaOH could be attributed to the effect of

increasing ionic strength that can shield the anionic pendants.

51

Figure ‎2.4 Reduced viscosity (sp/C) of a 1.0 g/dL solution of polymer PPB 2 (entry 7, Table 1) in salt-free

water versus equivalent of added NaOH at 23 C.

Viscosity data for PPB 2 (entry 7, Table 2−1) in neutral medium and in the presence of 1

equivalent of HCl and NaOH are presented in Figure 2−5. In the absence of added salt

(NaCl), the plot for (PPB 2 + 1 equiv NaOH) i.e. APP 3 system is concave upwards, a

typical case for a polyelectrolyte; the reduced viscosity increases slightly with decreasing

concentration of the polymer. Note that the dynamic equilibrium: APP 3 + H2O ⇌

PPB/APP 4 + OH- in aqueous solution via protonation of the weakly basic nitrogens in 3

is expected to move more and more towards the right as the concentration of the polymer

decreases. As a result, at higher dilution, a decrease in the reduced viscosity values could

be attributed to the increasing proportion of zwitterionic motifs in 4.

52

2.3.4 Basicity constants

In order to gain further information on the conformational transitions, we have

determined the basicity constants, Kio, and the corresponding ni values

relative to the

protonation of the tertiary amine and carboxylate in polymer APP 3 and monomer 1

(NaOH-treated) in salt-free water and 0.1 N NaCl solution. Basicity constants and the

corresponding ni values as well as the experimental details of the potentiometric titrations

are given in Tables 2−2 and 2−3.

The basicity constants log K1 for the protonation of the trivalent nitrogen of this polymer

are found to be “apparent” [130-131,152]

in salt-free as well as 0.1 N NaCl solution since the

n values are not equal to 1; n values were found to be 2.80 and 1.91, respectively. The

behavior of variation of log K1 with the degree of protonation () is known as

polyelectrolyte effect; polymer exhibiting a strong polyelectrolyte effect shows a large

change in log K in going from one end to the other end of the titration. The magnitude of

the n reflecting the polyelectrolyte effect is an index of accessibility of the proton to the

amine nitrogen during the protonation reaction. The basicity constant (log K1o) of the

amine group was found to be 8.58 and 7.65 in salt-free water and 0.1 N NaCl,

respectively (Tables 2−2 and 2−3). Since the n1 values are greater than 1, the approach

of the incoming protons to the amine nitrogens becomes more and more difficult with the

increasing degree of protonation (). The decrease in the overall negative charge density

in the macromolecule decreases the electrostatic field force that attracts the proton

thereby decreases basicity constant (log K) with the increase in degree of protonation ().

53

Figure ‎2.5 The viscosity behavior of the PPB 2, APP 3 and CPP 4 (obtained via PPB 2 from entry 7, Table

2−1) in salt-free water and 0.1 N NaCl at 30 ᴼC using an Ubbelohde viscometer

54

Figure ‎2.6 Plot for the apparent log K1 versus degree of protonation (a) for PPB 2-APE 3 system (entry 7,

Table 2−1) in salt-free water and 0.1 N NaCl.

55

Protonation of polymers is dictated by entropy effects associated with the release of water

molecules from the hydration shell of the repeating unit that is being protonated [147]

.

Comparison of Figure 2−5a vs. 2−5b reveals that APP 3 (i.e. PPB 2 + 1 equiv NaOH) in

salt-free water is more extended as indicated by higher viscosity values. The APP is thus

more hydrated (more water molecules in each hydration shell) than in salt solution (0.1 N

NaCl) where the polymer chain adopts a compact conformation due to screening of the

negative charges by the sodium ions. Logically, the contraction of the macromolecule

chain in salt-free water upon protonation of each repeating unit in APP 3 is larger (Figure

2−5a transforming into 2−5d) than in 0.1 N NaCl (Figure 2−5b transforming into 2−5c).

This would lead to the loss of greater number of water molecules from the hydration shell

of the repeating unit being protonated in salt-free water. This is reflected by the higher n1

value (2.80), greater basicity constant (log K1o: 8.58), and greater changes in the basicity

constant in salt-free water (Figure 6) than in 0.1 N NaCl.

The second basicity constants K2º and the n2 values for the protonation of the

P(=O)OEtO– group were determined as log K2º = 2.54, n2 = 0.69 in salt-free water; log

K2º = 2.76, n2 = 0.67 in 0.1 N NaCl. The slightly higher log K2º in 0.1 N NaCl could be

attributed to the higher viscosity value in the saline media (Figure 2−5c vs. 2−5d) in

which the macromolecule is more hydrated. Upon each protonation, greater number of

water molecules is thus released in 0.1 N NaCl thereby leading to the higher basicity

constant.

The basicity constant (log K1o) of the amine group in monomer 1, copolymer 4 and the

corresponding homopolymer [121]

at 23 ᴼC in salt-free water are determined to be

56

8.99, 8.58 and 10.5, respectively; while the respective values in 0.1 N NaCl were found

to be 8.74, 7.65 and 10.0. The incorporation of electron-withdrawing SO2 moiety has

thus resulted in the decrease of basicity constant of the nitrogens in copolymer 4 (in

compare to homopolymer) by a staggering ≥2 units of log K. We intend to study and

compare the chelating properties, including ion-selectivity, of co-(4) and its

corresponding homo-polymer [121]

to form polymer-heavy metal ion complexes from

waste water [125-127]

. While the decrease in basicity of the nitrogens on the copolymer may

have an adverse effect on the chelation process, the presence of lone pairs on the SO2

units may be beneficial to chelation.

2.4 Conclusions

We have, for the first time, synthesized a pH-responsive phosphonobetaine/SO2

copolymer (PPB) 2 using Butler’s cyclopolymerization process. The basicity constants

of the pH-triggerable amine and phosphonate functionalities have been determined. The

PPB 2 showed ‘antipolyelectrolyte’ behavior in salt-added media. The study

demonstrated a correlation between the basicity constants and viscosity values in salt-free

and salt-added solutions. The PPB was found to soluble in protic but insoluble in aprotic

solvents. The polymer was found to be soluble in the presence of Ca2+

ions thereby it

may find potential application, for instance, in desalination plants in inhibiting CaCO3

scaling by making soluble polymer-Ca2+

metal complex. The PPB is soluble in salt-free

as well as salt-added water as a result of the phosphonic acid pKa being > 2. The nature

and concentration of salt on the viscosity values have been determined; the

polyphosphobetaine showed higher intrinsic viscosity values in LiCl than in NaCl.

57

Tremendous difference in the basicity constants of the nitrogens in copolymer 4 and its

corresponding homopolymer [121]

would allow us to study and compare their

chelating properties and selectivity with heavy metal ions.

58

3 CHAPTER 3: SYNTHESIS OF A

POLYAMINOPHOSPHONATE AND ITS EVALUATION

AS AN ANTISCALANT IN DESALINATION PLANT

Taken from I. W. Kazi1, F. Rahman, and Shaikh A. Ali, Polyaminophosphonate and its

Evaluation as an Antiscalant in Desalination Plant, Polymer Engineering & Science.

DOI 10.1002/pen.23548

ABSTRACT:

The cationic monomer, N,N-Diallyl-3-(diethylphosphonato)propylammonium chloride,

was cyclopolymerized in aqueous solutions using t-butylhydroperoxide (TBHP) or

ammonium persulfate (APS) as initiators to afford a cationic polyelectrolyte (CPE)

having a (diethylphosphonato)propyl pendent. The CPE on acidic hydrolysis of the

diester groups gave pH-responsive polyzwitterionic acid (PZA) which on treatment with

one and two equivalents NaOH gave zwitterionic/anionic polyelectrolyte (ZAPE) and

dianionic polyelectrolyte (DAPE), respectively. The solution properties of the CPE, PZA,

ZAPE and DAPE were investigated in detail by viscometric technique. For the purpose

of comparison, the solution properties of the polymers were correlated to a structurally

similar polyzwitterion (PZ) having monoethylphosphonate and NH+ groups. When

performance evaluation was carried out for application in Reverse Osmosis (RO) plants,

DAPE at a concentration of 10 ppm in brackish water feed proved very effective as an

inhibitor against calcium sulfate scale.

KEYWORDS: Water-soluble polymers; Polyelectrolyte; cyclopolymerization;

polyaminophosphonate; calcium sulphate scale; antiscalant

59

3.1 INTRODUCTION

Butler’s cyclopolymerization protocol has led to the synthesis of a variety of cationic and

anionic polyelectrolytes [153]

as well as polybetaines (having charges of both algebraic

signs in the same repeating units) [25, 130,154-155]

,and polyampholytes (having repeating

units containing cationic and anionic charges with or without charge symmetry) [156]

. The

polymer-architecture, having the five-membered cyclic units embedded in the backbone,

has been recognized as the eighth major structural type of synthetic polymers [157-158]

.

These cyclopolymers are of significant scientific and technological interest;

poly(diallyldimethylammonium chloride) itself has over 1000 patents and publications;

over 33 million pounds of the polymer are sold annually for water treatment and another

2 million pounds are used for personal care formulation [1]

. The technical applications

based on coulombic attraction between the positively charged quaternary ammonium

polyelectrolytes and negatively charged macro-ions, surfactants, etc., have resulted in

different materials including membranes, modified surfaces, and coated particles,[152,159-

16].

The unquenched valency of nitrogen in diallylamine salts containing sulfonate and

carboxylate, and phosphonate functionalities as pendents led to the synthesis of a variety

of pH-responsive poly sulfo- [161]

, carbo- [162]

, and phosphono-betaines [121]

[163]

(i.e.,

polyzwitterions) [149 ,150.151]

. The intragroup, intra- and interchain electrostatic dipole-

dipole attractions among the dipolar groups in polyzwitterions lead to collapsed or

globular conformations which undergo globule-to-coil transitions (antipolyelectrolyte

60

effect) in the salt-added (e.g. NaCl) solutions owing to the neutralization of the ionically

cross-linked network in the collapsed conformation [3]

[149-150,164-165]

,. The high dipole

moment of a PZ makes it an excellent polar host matrix in which only target ions can

migrate[166-167]

. The pH-responsive PZs, whose structure and behavior seem to mimic

biopolymers, have been utilized in various medical fields [168-171]

, for efficient separations

of biomolecules [150]

and to develop procedures for DNA assay [172]

. They have also

drawn attention in the field of ion exchange; their abilities to chelate toxic trace metals

(Hg, Cd, Cu, and Ni) have been exploited in wastewater treatment [150],[171]

.

The polyphosphobetaines (containing pendent with a phosphate group) seem to mimic

phospholipid biomembranes and have offered many new applications [150,173]

. Recently,

Butler’s cyclopolymerization protocol has been applied in the syntheses of some

polyphosphonobetaines (having phosphonate group in the pendent) [120] [161,162,174-177]

,.

Extraordinary chelating properties of aminomethylphosphonic acid groups have been

exploited to form polymer-heavy metal ion complexes from waste water [104,149,178]

.

In pursuit of tailoring pH-responsive polymers, we describe herein the synthesis and

cyclopolymerization of a new cationic phosphonium monomer 2 (Scheme 3−4) to

cationic polyelectrolyte (CPE) 3 which was converted to pH-responsive polyzwitterion-

acid (PZA) 4, dianionic polyelectrolyte (DAPE) 6, zwitterionic/anionic polyelectrolyte

(ZAPE) 7. The polymerization of zwitterionic monomer 8 to polyzwitterion (PZ) 9 [161]

and its conversion to anionic polyelectrolyte (APE) 10, PZA 4, DAPE 6, and ZAPE 7

would allow us to correlate solution properties with the charge types and densities on the

polymer backbone. Antiscalants are chemical substances that reduce or prevent the

61

formation of scales or precipitation which is one of the major problems in operating

desalination plants [179]

. One important objective of this work is to investigate the

antiscalant properties of the synthesized polymer DAPE 6. The pH-responsive

polyaminophosphonate having the phosphonate and amine groups separated by a three-

carbon spacer would thus be prepared for the first time using cyclopolymerization

protocol and used as a novel antiscalant in inhibiting the formation of calcium sulfate

scale. The work would thus pave the way to synthesize and utilize many such polymers

having different length of the spacer separating the amine and phophonate functionalities.

62

Scheme ‎3-1

63

3.2 EXPERIMENTAL

3.2.1 Physical Methods

Elemental analysis was carried out on a Perkin Elmer Elemental Analyzer Series II

Model 2400. IR spectra have been recorded on a Perkin Elmer 16F PC FTIR

spectrometer. The 31

P, 13

C, and 1H NMR spectra of the polymers have been measured in

CDCl3 (using TMS as internal standard) or D2O (using HOD signal at 4.65 ppm and

dioxane 13

C peak at 67.4 ppm as internal standards) on a JEOL LA 500 MHz

spectrometer. 31

P was referenced with 85% H3PO4 in DMSO. Viscosity measurements

were made by Ubbelohde viscometer (having Viscometer Constant of 0.005718 cSt/s at

all temperatures) using CO2-free water under N2 in order to avoid CO2 absorption that

may affect the viscosity data. Molecular weights of some synthesized polymers were

determined by GPC analysis using Viscotek GPCmax VE 2001. The system was

calibrated with nine polyethylene oxide monodispersed standards at 30°C using two

Viscotek columns G5000 and G6000 in series. The Atomic

Absorption Spectrometer AAnalyist-100 PerkinElmer was used to determine the

concentration of metal ions in evaluating the effectiveness of the antiscalant.

For the determination of molecular weights, the polymer DAPE 6 derived from CPE 3

and PZ 9 were analyzed using an aqueous solution of 0.1 N NaNO3 as the eluant.

Refractive Index and viscometer detectors were used to determine molar mass of the

polymers.

64

3.2.2 Materials

Ammonium persulfate, t-butylhydroperoxide (70% aqueous solution), anhydrous CaCl2,

Na2SO4, 1,3-dibromopropane, triethyl phosphite, and diallyl amine from Fluka Chemie

AG (Buchs, Switzerland) were used as received. For dialysis, a Spectra/Por membrane

with a molecular weight cut-off (MWCO) value of 6000-8000 was purchased from

Spectrum Laboratories, Inc. All glassware was cleaned with deionized water. N,N-

Diallyl-3-(diethylphosphonato)propylamine (1) was prepared as described [161]

by

reacting diallylamine and 1-Bromo-3-(diethylphosphonato)propane.

3.2.3 Monomer and polymer synthesis

3.2.3.1 N,N-Diallyl-3-(diethylphosphonato)propylammonium chloride (2).

To an ice-cooled stirred solution of 1 (41.3 g, 0.15 mol) in diethyl ether (300 cm3),

moisture-free HCl was bubbled until the supernatant ether layer became clear and further

production of milky solution seized. The separated chloride salt was washed several

times with ether to obtain 2 as a viscous liquid which was dried under vacuum at 40 ᴼC to

a constant weight (45.2 g, 97%). The viscous liquid was solidified when kept inside a

freezer. An analytical sample was prepared by crystallizing 2 from

acetone/ether/methanol mixture. Mp 57-59°C (closed capillary); the highly hygroscopic

salt gave an approximate elemental analysis: (Found: C, 49.6; H, 8.97; N, 4.3.

C13H27ClNO3P requires C, 50.08; H, 8.73; N, 4.49 %); max (KBr) 3435, 2985, 2930,

2630, 2639, 1646, 1457, 1218, 1163, 1025, 963 and 768 cm-1

; H (D2O) 1.21 (6 H, t, J 7.0

Hz), 1.89 (4H, m), 3.14 (2 H, m), 3.69 (4 H, m), 4.03 (4 H, m), 5.51 (4 H, m), 5.82 (2 H,

65

m); C (125 MHz, D2O): 16.49 (s, 2C, Me), 17.74 (s, 1C, PCH2CH2), 21.84 (d, 1C, d,

PCH2, 1J(PC) 140 Hz), 52.30 (1C, d, PCH2CH2CH2,

3J(PC) 17.5 Hz), 55.80 (s, 2C, =CH-

CH2), 64.37 (d, 2C, OCH2CH3, 2J (PC) 7.2 Hz), 126.22 (s, 2C, =CH), 127.61 (s, 2C,

CH2=); P (202 MHz, D2O31.40(m, 1P). 13

C spectral assignments were supported by

DEPT 135 NMR analysis.

3.2.3.2 General Procedure for the polymerization of Cationic Monomer 2.

To a solution of monomer 2 in deionized water in a 10 cm3 round bottomed

flask purged with N2 was added the required amount of the initiator (as listed in

Table 3−1). The mixture was stirred in the closed flask at the specified

temperature for a specified time. The transparent reaction mixture was dialyzed

against deionized water for 24 h. The polymer solution of cationic

polyelectrolyte (CPE) polydiallyl(diethylphosphonato)propylammonium

chloride (3) was then freeze-dried. The onset of thermal decomposition (closed

capillary): 300-310 ᴼ

C (decomposed, turned black); (Found: C, 49.8; H, 8.8; N,

4.4. C13H27ClNO3P requires C, 50.08; H, 8.73; N, 4.49 %); max (KBr) 3400

(very broad almost engulfing the CH stretching vibrations), 2989, 2945, 1652,

1461, 1398, 1219, 1127, 1025, 968, 794, 705, 619, and 542 cm-1

; P (202 MHz,

D2O): 33.84 (s, major) and 26.09 (s, minor) in a 75:25 ratio.

66

3.2.3.3 Acidic Hydrolysis of CPE 3 to PZA 4.

A solution of polymer 3 (3.22 g, 10.3 mmol) (entry 2, Table 3−1) in HCl (25 cm3) and

water (20 cm3) was hydrolyzed in a closed vessel at 90

oC for 48 h. The homogeneous

mixture was cooled to room temperature and dialyzed against deionized water for 48 h.

Some polymer settled down on the bottom of the dialysis bag. The whole mixture was

then freeze-dried to obtain poly [3-(N,N-diallylammonio)propanephosphonic acid] 4 as a

creamy white powder (2.12 g, 94%). The onset of thermal decomposition (closed

capillary): 310-320oC (dec, turned light brown). (Found: C, 49.0; H, 8.4; N, 6.2%.

C9H18NO3P requires C, 49.31; H, 8.28; N, 6.39%); max (KBr) 3450, 2952, 2730, 1653,

1463, 1144, 1053, 907, 768, 709, and 543 cm-1

.

3.2.3.4 Basification of PZA 4 to dianionic polyelectrolyte (DAPE) 6.

A mixture of PZA 4 (derived from hydrolysis of CPE 3 from entry 2, Table 3−1) (0.876

g, 4.0 mmol) in water (5 cm3) was neutralized with 1.0 N NaOH (8.0 cm

3, 8.0 mmol).

After the mixture became homogeneous, the solution was freeze-dried to obtain

poly[disodium 3-(N,N-diallylamino)propanephosphonate] 6 as a creamy white powder

(1.02 g, 97%). The onset of thermal decomposition (closed capillary): above 300 ᴼ

C

(turned brown), did not melt even at 370 ᴼC; (Found: C, 40.8; H, 6.4; N, 5.1.

C9H16NNa2O3P requires C, 41.07; H, 6.13; N, 5.32%); max (KBr) 3475 (very broad

engulfing the CH stretching vibrations), 2920, 2820, 1660, 1451, 1390, 1306, 1222, 1060,

973, 783, and 613 cm-1

. P (202 MHz, D2O22.60 (s, 1P).

67

3.2.3.5 Basification of PZA 4 to zwitterionic anionic polyelectrolyte (ZAPE) 7.

A mixture of PZA 4 (derived from hydrolysis of CPE 3 from entry 2, Table 3−1) (0.876

g, 4.0 mmol) in water (8 cm3) was neutralized with 1.0 N NaOH (4.0 cm

3, 4.0 mmol).

After the mixture became homogeneous, the solution was freeze-dried to obtain

poly[sodium 3-(N,N-diallylammonio)propanephosphonate] (7) as a creamy white powder

(0.894 g, 93%). The onset of thermal decomposition (closed capillary): Neither change

in color nor melted up to 330oC; (Found: C, 44.5; H, 7.35; N, 5.6. C9H17NNaO3P requires

C, 44.82; H, 7.10; N, 5.81%); max (KBr) 3790, 2962, 2929, 2852, 1458, 1413, 1381,

1060, 974, 715, and 559 cm-1

; P (202 MHz, D2O: 20.81 (s, 1P).

3.2.3.6 Synthesis and polymerization of zwitterionic monomer 8 and conversion of the

resultant PZ 9 to PZA 4, DAPE 6, ZAPE 7 and anionic polyelectrolyte (APE)

10.

Zwttreionic monomer 8 was synthesised and polymerized to obtain PZ 9 using procedure

as described [161]

. A solution of monomer 8 (6.06 g, 24.3 mmol) in 0.5 N NaCl (2.02 g)

was polymerized using initiator TBHP (125 mg) at 85oC for 48 h. The reaction mixture

was dialyzed against deionized water for 48 h to remove the unreacted monomer and

NaCl. The polymer solution was then freeze-dried to obtain PZ 9 in 59% yield. The

intrinsic viscosity [] at 30oC was determined to be 0.0988 dL/g in salt-free water (Table

3−2). PZ 9 was hydrolyzed to obtain PZA 4 (85%) which was then converted to DAPE 6,

ZAPE 7 using procedures as described above. Likewise, PZ 9 was converted to APE 10

using 1 equivalent NaOH [161]

68

3.2.4 Evaluation of antiscalant behavior

Analysis of feed water and reject brine in Reverse Osmosis (RO) Plant at King Fahd

University of Petroleum & Minerals, Dhahran, Saudi Arabia, revealed the concentration

of Ca2+

as 281.2 ppm in the brackish feed water and 867.7 ppm in the reject brine; the

corresponding concentration of SO42-

in the feed water and reject brine was found to be

611 and 2,100 ppm, respectively [180]

. The composition of the above reject brine at 70%

recovery is referred to as 1 CB (concentrated brine). The evaluation of the newly

developed scale inhibitor DAPE 6 was performed in a solution containing 2.3 times the

concentration of Ca2+

and SO42-

than 1 CB. The 2.3 CB solutions would be supersaturated

with respect to CaSO4.

Solutions containing Ca2+

and SO42-

ions equals to 4.6 times of the concentrated brine (1

CB) were prepared by dissolving the calculated amount of CaCl2 and Na2SO4,

respectively, in deionized water. 4.6 CB calcium chloride solution (60 mL) at a dose

level of 20 ppm DAPE 6 was taken in a two necked round bottom flask and heated to

50ºC 1ºC. A preheated (50 ºC) solution of 4.6 CB sodium sulfate (60 mL) was added

quickly to the flask, the content of which was stirred at 300 rpm using a magnetic stir-bar.

The resultant solution containing 10 ppm of DAPE 6 thus becomes 2.3 CB which is

2.3×866.7 mg/L i.e. 1993 mg/L in Ca2+

and 2.3×2100 mg/L i.e. 4830 mg/L in SO42-

. 200

L samples were taken at different interval of time through 0.45 micron filter (millipore)

to measure the Ca2+

ions remaining in the solution using Atomic Absorption spectrometer

(Table 3−3).

69

3.3 Results and Discussion

3.3.1 Synthesis of monomer and polymers

New cationic monomer 2 was prepared in excellent yield by bubbling anhydrous HCl

through a solution of 1 [161]

in ether (Scheme 3−1). The monomer underwent

cyclopolymerization in aqueous solution containing 70 wt% monomer to give CPE 3.

The results of the polymerization reaction are given in Table 3−1. Initiator TBHP (entry

2) gave the polymer in better yield than initiator APS (entry 1). The lower yields and

intrinsic viscosity values (Table 3−1) could be a result of chain transfer between

Table ‎3-1 Cyclopolymerization of Cationic Monomer 2a to CPE 3

Entry

Initiator

(mg)

Temp

(°C)

Time

(h)

Yield

(%)

Intrinsic

Viscosityb

(dl g-1

)

1

APS (400) 85 48 49 0.0934

2

TBHP (270) 85 48 61 0.101 a Polymerization reactions were carried out in aqueous solution of

monomer (20 mmol) (70 w/w% monomer) in the presence of

ammonium persulfate (APS) or tertiary butylhydroperoxide (TBHP). b

Viscosity of 1-0.25 % polymer solution in 0.1 N NaCl at 30 ± 0.1 oC

was measured with an Ubbelohde Viscometer (K=0.005718). The

average of three readings (for the time of flow) having standard deviation

within 0.3 seconds are taken for the viscosity plots.

70

polymer and monomer through the alkoxy group attached to the P atom [181]

. Acidic

hydrolysis of CPE 3 afforded polyzwitterionic acid PZA 4 (>90% yield). PZA 4 on

treatment with 2 and 1 equivalent of NaOH afforded dianionic polyelectrolyte (DAPE) 6

and zwitterionic/anionic polyelectrolyte (ZAPE) 7, respectively. ZAPE 7 contains an

interesting blend of zwitterionic as well as anionic groups in the same repeating unit.

For the purpose of comparison, PZ 9 was prepared [161]

via cyclopolymerization of

zwitterionic monoester 8 (Scheme 3−1). PZ 9 was treated with one equivalent NaOH to

obtain a solution of anionic polyelectrolyte (APE) 10. Using acidic hydrolysis, PZ 9 was

also converted into PZA 4, DAPE 6, and ZAPE 7.

Polyphosphonates 3-7 were found to be very stable and did not show any appreciable

decomposition or color change up to 300 C. While CPE 3, DAPE 6 and ZAPE 7 were

found to be readily soluble in salt-free water, PZA 4 remained insoluble. A cloudy

mixture of 3 wt% PZA 4 in salt-free water became transparent in 0.03 M NaCl. The PZA

was also found to be soluble in 0.1 N HCl. Even though overwhelming majority of the

reported polyzwitterions were found to be insoluble in water [160,159,163,182]

, PZ 9 remained

soluble both in salt-free and salt-added water as a result of the extensive hydration of the

O- and steric crowding exerted by OCH2CH3 which prevent effective zwitterionic

interaction with the cationic nitrogens [161].

71

3.3.2 Infrared and NMR spectra

The strong absorptions at 1127 and 1025 cm-1

in the IR spectrum of CPE 3 were

attributed to the stretching frequency of P=O and P-O-C, respectively. For PZA 4, DAPE

6 and ZAPE 7, the peaks at 1053, 1060, and 1060 cm-1

were assigned to the stretching

frequency of P=O. 1H and

13C NMR spectra of the monomer and polymers are displayed

in Figs. 3−1 and 3−2, respectively. The absence of any residual alkene proton or carbon

signal in the spectra suggested the chain transfer process [183]

for the termination reaction.

Figure ‎3.1 1H NMR spectrum of monomer 2, CPE 3, DAPE 6 and ZAPE 7 in D2O

72

Figure ‎3.2 13C NMR spectrum of monomer 2, CPE 3, DAPE 6 and ZAPE 7 in D2O

73

The assignments of the 13

C peaks are based on earlier works [44,184-187]

, on quaternary

ammonium salt monomers which undergo cyclopolymerization to afford kinetically

favorable five-membered ring structure whose substituents at the C-b can either be in the

symmetrical cis (major) or unsymmetrical trans (minor) dispositions (Scheme 3−2).

Scheme ‎3-2

Integration of the signals yielded the cis/trans ratio of the ring substituents to be 75:25;

similar ratios are observed for many a Butler’s cyclopolymerization process [4,41]

[41]. 31

P

NMR signal for monomer 2, CPE 3, DAPE 6 and ZAPE 7 appeared at 31.4, 33.8, 22.6

and 20.8 ppm, respectively. The upfield shift of P signal in 6 and 7 is attributed to the

higher electron density around P as a result of negatively charged oxygens.

74

3.3.3 Viscosity measurements

Viscosity data as evaluated by the Huggins equation: sp/C = [+ k [C are given

in Table 3−2. The Huggins viscosity plots for CPE 3, DAPE 6 and ZAPE 7 (having

identical degree of polymerization) in salt-free water remain concave upwards like any

polyelectrolytes (Fig. 3−3). In the lower concentration range, the sequence of decreasing

reduced viscosity was found to be:

CPE 3 > ZAPE 7 > and DAPE 6

One would have expected dianionic 6 to have higher viscosity values than

zwitterionc/anionic 7 since the former has higher net charges than the later. A possible

rationale behind this observation could be attributed to the increased repulsion among

positively charged nitrogens in 7, hence expansion of the polymer chain. Note that the

increased distance between the negatively charged oxygens in the neighboring repeating

units in DAPE 6 leads to a less effective repulsion. Viscosity plots became linear in the

presence of 0.1 N NaCl, and the sequence of decreasing intrinsic viscosity was found to

be (Fig. 3, Table 3−2):

75

Figure ‎3.3 The viscosity behavior of CPE 3, DAPE 6, and ZAPE 7 in salt-free water and 0.1 N NaCl at

30oC using an Ubbelohde Viscometer

76

Table ‎3-2 Effect of NaCl on the intrinsic viscosity ([a and Huggins constant (K) of PZE 8 (entry 2, Table

3−1).

Polymer NaCl

(N) []

(dL/g)

Correlation

coefficient

(R2)

Slope k WM (PDI)d

CPE 3 0.1 0.101 0.9968 0.00290 0.284

DAPE 6b

0.1 0.125 0.9839 0.00961 0.614 27,300 2.2

ZAPE 7b

0.1 0.114 0.9970 0.0215 1.65

0.5 0.114 0.9887 0.00821 0.631

1.0 0.113 0.9893 0.00901 0.705

PZ 9

0 0.0988 0.9945 0.0192 1.97

0.1 0.114 0.9987 0.0253 1.95

DAPE 6c

0.1 0.266 0.9998 0.0287 0.406 62,500 2.1

ZAPE 7c

0.1 0.244 0.9918 0.0436 0.732

APE 10c

0.1 0.147 0.9933 0.502 2.32

aViscosity of 1-0.25 % polymer solution in 0.1 N NaCl at 30 ± 0.1

oC was

measured with an Ubbelohde Viscometer (K=0.005718). The average of

three readings (for the time of flow) having standard deviation within 0.3

seconds are taken for the viscosity plots.

bderived via CPE 3.

cderived via PZ 9.

dPolydispersity Index.

DAPE 6 > ZAPE 7 > and CPE 3

The lowest value for the Huggins constant k in the case of 3 in comparison to 6 and 7

may be associated with an increased polymer-solvent interaction. Hydration shell of Na+

77

is generally fairly large; hence the distance of closest approach is not sufficient to

effectively neutralize the charge on the pendent phosphonate anions in 6 and 7. However,

Cl- ions are very effective in shielding, hence minimizing the repulsion among positive

nitrogens in 3 and 7 which leads to lower hydrodynamic volumes and intrinsic viscosities

[].

The decrease and increase of intrinsic viscosity in the presence of an added salt is a

demonstration of “polyelectrolyte” and “anti-polyelectrolyte” behavior of a

polyelectrolyte (cationic or anionic) and a polyzwitterion, respectively [86,159,163,185]

,. Note

that the intrinsic viscosity of ZAPE 7 in 0.1 N, 0.5 N, and 1.0 N NaCl remained almost

unchanged (~0.114 dL/g) (Table 3−2). ZAPE 7 has dual groups of zwitterion and anion,

and it is the anionic portion that dictates the viscosity plot (Fig. 3−3). The presence of

NaCl leads to a contraction and expansion of the polymer chain of a polyelectrolyte and

polyzwitterion, respectively [86,159,163,185]

,. These opposite forces cancel the overall effect

of NaCl in the solution, thereby leading to the unchanged intrinsic viscosity values for

ZAPE 7 in the presence of various concentrations of the salt.

78

Figure ‎3.4 The viscosity behavior of PZ 9, DAPE 6, and ZAPE 7 in salt-free water and 0.1 N NaCl at

30oC using an Ubbelohde Viscometer

The viscosity plot for PZ 9 in the absence or presence of added salt (NaCl) remains

linear (Fig. 3.4). The intrinsic viscosities in salt-free and 0.1 N NaCl were found to be

0.0988 and 0.144 dL/g, respectively; an increase in the intrinsic viscosity in the presence

of NaCl is a demonstration of the “anti-polyelectrolyte” behavior of the PZ 9. As

discussed earlier, the Cl- ions shield the positive nitrogens more effectively than the

shielding of phophonate anions by the hydrated Na+ ions. As a result, the zwitterionic

79

moiety is left with a net negative charge that leads to repulsion hence expansion of the

Figure ‎3.5 The viscosity behavior of CPE 3, DAPE 6 (via CPE 3), and DAPE 6 (via PZ 9), 0.1 N NaCl at

30oC using an Ubbelohde Viscometer.

polymer chains. While CPE 3, ZAPE 7, and DAPE 6 (derived from CPE 3) have

intrinsic viscosity values of 0.101, 0.114, and 0.125 dL/g, respectively, the corresponding

values for PZ 9, ZAPE 7, and DAPE 6 (derived from PZ 9) are found to be 0.114, 0.244,

and 0.266 dL/g in 0.1 N NaCl (Table 3−2). Note that CPE 3 and PZ 9 have similar []

(0.101 vs. 0.114 dL/g) in 0.1 N NaCl, while the DAPE 6 and ZAPE 7 derived from PZ 9

have twice the []s of the corresponding polymers derived from CPE 3 (Fig. 3−5, Table

3−2) as confirmed by the higher WM of DAPE 6 derived from PZ 9 (Table 3−2). This

80

indicates that even though PZ 9 has higher molar mass than that of CPE 3, yet they have

similar []s as a result of the former having zwitterionic groups that leads to contraction

of the polymer chains.

3.3.4 Antiscalant Evaluation:


CaCO3, CaSO4, Mg(OH)2), corrosion products, polymeric silica and suspended matter.

Davey [182]

presented an excellent review on the role of additives in precipitation

processes. The specific mechanism of inhibition of scaling is sequestration or the

capability of forming stable complexes with polyvalent cations. The antiscalant treated

solutions are evidently stabilized in some manner involving alteration in crystal

morphology at the time of nucleation and subsequent inhibition in growth rate [188]

.

Commonly used antiscalants are derived from three chemical families: condensed

poly(phosphate)s, organophosphates, and polyelectrolytes [1,189]

,. The anionic form of the

antiscalants helps prevent scale formation by sequestering the cations. Extraordinary

chelating properties of compounds containing aminomethylphosphonic acid groups in the

molecule have attracted considerable attention to synthesize low molecular-weight

chelating agents containing these functional groups that should be able to form polymer-

heavy metal ion complexes from waste water [179,180,181]

.

In the Reverse Osmosis (RO) process, the feed water splits into product water and reject

brine streams. The dissolved salts in the feed water are concentrated in the reject brine

stream. If supersaturation occurs and their solubility limits are exceeded, precipitation or

81

scaling will occur. The percent scale inhibition is calculated using the following

Equation:

100][][

][][%

)(

2

)(

2

)(

2

)(

2

0

tblanktinhibited

tblanktinhibited

CaCa

CaCaInhibitionScale

where )(tinhibited

2

0][Ca is the initial concentration at time zero, [Ca

2+] inhibited (t) and

[Ca2+

]blank (t) are the concentration in the inhibited and blank solutions at time t. The blank

at the zero time was a supersaturated solution of CaSO4 containing 1993 mg/L Ca2+

(using CaCl2) and 4830 mg/L SO42-

(using Na2SO4) which is equivalent to 2.3 times the

concentration of a concentrated brine (CB) (Experimental). Spontaneous precipitation of

CaSO4 was observed in the case of the blank solution with the decrease in the

concentration of Ca2+

(Table 3−3, Fig. 3−6).

82

Table ‎3-3 Concentration of Ca2+ at various times at 50°C in the absencea and presencea of antiscalant

additive DAPE 6 (10 mg/L).

Time

(min)

solutiona with Inhibitor

Blank

solutiona

Scale

Inhibition

(%)

Ca2+

(mg/L)

Ca2+

(mg/L)

0 1990 1990 −

6 1988 660 99.8

180 1984 640 99.6

420 1960 630 97.8

1800 1930 620 95.6 aboth solution contained Ca

2+ and SO4

2- at a concentration of 2.3

times the concentration of concentrated brine (CB) i.e. [Ca2+

]

=1993 mg/L and [SO42-

] = 4830 mg/L

Figure ‎3.6 Precipitation behavior of supersaturated solution of CaSO4 in the presence (10 ppm) and

absence of DAPE 6

83

However, with the addition of DAPE 6 to the concentrated brine solution, [Ca2+

]

remained almost constant for about 180 min with 99.6 % scale inhibition. After the

elapse of 30 h (i.e. 1800 min), [Ca2+

] dropped from 1990 mg/L to 1930 mg/L resulting in

a scale inhibition of 95.6%. This indicates that the additive is very effective against

precipitation of CaSO4 at 50ºC in a 2.3 CB and thus suitable for its application in the

prevention of scaling in RO desalination plants.

3.4 Conclusions

Using Butler’s cyclopolymerization process, we have, for the first time, synthesized

cationic polyelectrolyte (CPE) 3 containing a pendant having three carbon spacer

separating the diethylphosphonate and NH+. Upon acidic hydrolysis of the phophonate

esters, CPE 3 was readily converted into pH-responsive PZA 4, DAPE 6 and ZAPE 7.

The solution properties of the polymers were correlated to the structurally similar

polyzwitterion (PZ) 9 having monoethylphosphonate and NH+ groups. Evaluation of the

antiscalant properties using concentrated brines revealed that DAPE 6 at a meager

concentration of 10 ppm is very effective in inhibiting the formation of calcium sulfate

scale, and as such it can be used effectively as an antiscalant in Reverse Osmosis plant.

84

4 CHAPTER 4: SYNTHESIS OF A

DIALLYLAMMONIOPROPANEPHOSPHONATE-ALT-

SULFUR DIOXIDE COPOLYMER AND ITS

EVALUATION AS AN ANTISCALANT IN

DESALINATION PLANT

Taken from Shaikh A. Ali, I. W. Kazi, and F. Rahman, Synthesis of a

diallylammoniopropanephosphonate-alt-sulfur dioxide copolymer and its

evaluation as an antiscalant in Desalination Plant Polymer International: DOI

10.1002/pi.4539

ABSTRACT

The cationic monomer, N,N-Diallyl-3-(diethylphosphonato)propylammonium chloride,

was cyclocopolymerized with sulfur dioxide in dimthylsulfoxide (DMSO) using

azoisobutyronitrile (AIBN) as initiator to afford a cationic polyelectrolyte (CPE) having a

(diethylphosphonato)propylpedent. The CPE on acidic hydrolysis of the diester groups

gave pH-responsive polyzwitterionic acid (PZA) which on treatment with one and two

equivalents NaOH gave zwitterionic/anionic polyelectrolyte (ZAPE) and dianionic

polyelectrolyte (DAPE), respectively. The solution properties of the CPE, PZA, ZAPE

and DAPE were investigated in detail by viscometric technique. For the purpose of

comparison, the solution properties of the polymers were correlated to the structurally

similar polyzwitterion (PZ) prepared from copolymerization of the corresponding

zwitterionic monomer ethyl 3-(N,N-diallylammonio)propanephosphonate and sulfur

dioxide. Evaluation of antiscaling properties using concentrated brine solutions revealed

that DAPE at a meager concentration of 10 ppm is very effective in inhibiting the

85

formation of calcium sulfate scale, and as such can be used effectively as an antiscalant in

Reverse Osmosis plant.

KEYWORDS: Polyelectrolyte; polyphophonobetaine; polyaminophosphonate;

calcium sulphate scale; antiscalant.

4.1 INTRODUCTION

The polymer architecture constructed via Butler’s cyclopolymerization protocol

involving diallylammonium monomers has been recognized as the eighth most important

structural feature for synthetic polymers.[190-191]

The cyclopolymerization has led to the

synthesis of a variety of cationic and anionic polyelectrolytes [192]

as well as polybetaines

(i.e. PZs) [25,130,193-194]

, and polyampholytes [195]

, all having five-membered rings

embedded into their backbones. The zwitterionic diallylammonio monomers with charges

of both algebraic signs in the same unit and having sulfonate, carboxylate, and

phosphonate functionalities attached to the alkyl pendents have provided entries into the

synthesis of a variety of pH-responsive polysulfo-[196]

, carbo-[197]

, and

phosphonobetaines [120-121,185,197,198-200]

as well as copolymers with sulfur dioxide.[139-

140,210,211,201], ,

Butler’s cyclopolymers are of significant scientific and technological interest [202-203]

:

Poly(diallyldimethylammonium chloride) itself has over 1000 patents and publications;

over 33 million pounds of the polymer alone are sold annually for water treatment, and

86

another 2 million pounds are used for personal care formulations.[3]

The synthetic PZs′

structural and behavioral similarities with biopolymers like life-mediating proteins or

DNA have offered many applications in various fields including medical [191-193,204]

,

bioseparations [201]

, and DNA assay[205]

. The high dipole moment of PZs make them

excellent polar host matrices in which only target ions can migrate. [206-207]

They also have

drawn attention in the field of ion exchange; their abilities to chelate toxic trace metals

(Hg, Cd, Cu, and Ni) have been exploited in wastewater treatment. [201,208],

As a result of strong intragroup as well as intra- and interchain electrostatic dipole-dipole

attractions among the dipolar groups, the PZs, unlike cationic or anionic polyelectrolytes,

are usually insoluble in salt-free water owing to their existence in an ionically cross-

linked network in a collapsed or globular conformation.[3,200,201,209-211]

A PZ exhibits anti-

polyelectrolyte behavior, i.e., enhancement in viscosity and solubility in the presence of

added salts (e.g. NaCl) owing to the neutralization of the ionic cross-links.[32,104,228]

, The

Na+ and Cl

- ions shield (i.e., neutralize) the negative and positive charges in a dipolar

group, respectively, to different extents thereby leaving a net charge, repulsion among

which leads to globule-to-coil transitions as a result of chain expansion.

Extraordinary chelating properties of aminomethylphosphonic acid groups have been

exploited to form polymer-metal ion complexes from wastewater.[145,149-150]

Ionomers

containing phosphonic acid groups have been used in dental composites [146]

proton

conducting polymer electrolyte fuel cells.[147,212]

, Our interest in pH-responsive ionic

polymers containing aminophosphonate groups led us to synthesize a cationic monomer 1

which is reported to give its homocyclopolymer in relatively low yields (49-61%)

87

(Scheme 4−1).[213]

We describe herein the cocyclopolymerization of 1 with SO2 to a

cationic polyelectrolyte 2 which would then be converted to a variety of pH-responsive

polymers: polyzwitterion-acid (PZA) 3, dianionic polyelectrolyte (DAPE) 5,

zwitterionic/anionic polyelectrolyte (ZAPE) 6 as outlined in Scheme 4−1. Antiscalants

are chemical substances

88

Synthesis protocol for the polyaminopropanephosphonate-alt-sulfur dioxide copolymers

Scheme ‎4-1

H+/H2O

7: zwitterion

NH (CH2)3

P OO

EtO

Cl

PZA 3

8: polyzwitterion (PZ)

H+

H2O

3: polyzwitterions-acid

(PZA)

2: cationic polyelectrolyte (CPE)

5: dianionic polyelectrolyte

(DAPE)

NaOH2 equiv.

6: zwitterionic/anionicpolyelectrolyte (ZAPE)

6 M HCl NaOH1 equiv.

4: cationic poly-

electrolyte (CPE)

Cl

[ ] n

NH

S

O

O

(CH2)3

P OHO

HO

[ ] n

N

S

O

O

(CH2)3

(Na+ -O)2P O

HCl

1 equiv.

Cl

[ ] n

NH

S

O

O

(CH2)3

(EtO)2P O

[ ] n

N

S

O

O

(CH2)3

P OO

Na+ -O

H

[ ] n

N

S

O

O

(CH2)3

P OO

HO

H

[ ] n

NH

S

O

O

(CH2)3

P OO

EtO

NaOH1 or 2 equiv

1: Cationic monomer

NH (CH2)3

(EtO)2P O

Cl

ZAPE 6 or DAPE 5

9: anionic poly-

elcetrolyte (APE)

[ ] n

N

S

O

O

(CH2)3

P O Na+ -O

EtO

NaOH

SO2

AIBNDMSO

SO2

AIBNDMSO

89

that reduce or prevent the formation of scales or precipitation which is one of the major

problems in operating desalination plants.[206]

One important objective of this work is to

investigate the effect of SO2 spacer on the antiscalant properties of the synthesized

polymer DAPE 5. The pH-responsive polyaminophosphonate-alt-sulfur dioxide

copolymer PZA 3 having the phosphonate and amine groups separated by a three-carbon

spacer along with the presence of backbone stiffening SO2 units would thus be prepared

for the first time via Butler’s cyclopolymerization protocol and used as a novel

antiscalant in inhibiting the formation of calcium sulfate scale. The work would pave the

way to synthesize and utilize many such sulfur dioxide copolymers having different

length of the spacer separating the amine and phosphonate functionalities.

4.2 EXPERIMENTAL


Elemental analysis was carried out on a Perkin Elmer Elemental Analyzer Series II

Model 2400. IR spectra have been recorded on a Perkin Elmer 16F PC FTIR

spectrometer. The 31

P, 13

C, and 1H NMR spectra of the polymers have been measured in

CDCl3 (using TMS as internal standard) or D2O (using HOD signal at 4.65 ppm and

dioxane 13

C peak at 67.4 ppm as internal standards) on a JEOL LA 500 MHz

spectrometer. 31

P was referenced with 85% H3PO4 in DMSO. Viscosity measurements

were made by Ubbelohde viscometer (having Viscometer Constant of 0.005718 cSt/s at

all temperatures) using CO2-free water under N2 in order to avoid CO2 absorption that

90

may affect the viscosity data. Molecular weights of some synthesized polymers were

determined by the GPC measurement performed on a Agilent 1200 series apparatus

equipped with a Refractive Index (RI) detector and PL aquagel-OH MIXED column,

using polyethylene oxide/glycol as a standard and water as eluent at a flow rate of 1.0

mL/ min at 25 ᴼC. Thermogravimetric analysis (TGA) experiments were carried out using

Shimadzu DTG-60H equipment. The samples were heated from 25 ºC to 800 ºC at 10 ºC

/min under air.

4.2.2 Materials

AIBN from Fluka AG was purified by crystallization from a chloroform-ethanol mixture.

DMSO was dried over calcium hydride overnight and then distilled at a boiling point of

64-65C (4 mmHg). For dialysis, a Spectra/Por membrane with a molecular weight cut-

off (MWCO) value of 6000-8000 was purchased from Spectrum Laboratories, Inc. The

amine salt N,N-diallyl-3-(diethylphosphonato)propylammonium chloride (1) was

prepared by bubbling dry HCl through a solution of N,N-Diallyl-3-

(diethylphosphonato)propylamine in ether as described.[214]

General procedure

4.2.2.1 copolymerization of monomer 1 with SO2

All the polymerizations were carried out using conditions as described in Table 4−1. In a

typical experiment (Entry 7, Table 4−1), SO2 (20 mmol) was absorbed in a solution of the

monomer 1 (20 mmol) in DMSO (5.2 g). The initiator AIBN (80 mg) was then added

under N2 and the reaction mixture was stirred using a magnetic stir-bar at 60 ᴼC for 5 h.

91

Table ‎4-1 Cyclocopolymerization of the cationic monomer 1 with sulfur dioxidea to cationic polyelectrolyte

(CPE) 2

The polymer was precipitated in acetone, grinded to powder, filtered and washed with hot

acetone. The resulting CPE polydiallyl(diethylphosphonato)propylammonium chloride-

alt-sulfur dioxide (2), a white polymer, was dried under vacuum at 55 ᴼC to a constant

weight. The onset of thermal decomposition (Closed capillary) at 250-260 ᴼC

(decomposed, turned black); (Found: C, 41.2; H, 7.4; N, 3.55; S, 8.3. C13H27ClNO5PS

Entry

Monomer

(mmol)

AIBN

(mg)

DMSO

(g)

Yield

(%)

Intrinsic

Viscosityb

(dL g-1

)

WM

(PDI)

1 10 15 2.6 19 0.154 − −

2

10 30 2.6 74 1.06 − −

3

10 50 2.6 76 0.382 − −

4

10 50 3.0 67 0.266 − −

5 10 70 2.6 85 0.976 176,000 2.1

6 20 70 5.2 80 0.432 64,500 2.2

7 20 80 5.2 72 1.27 245,000 2.1

aPolymerization reactions were carried out using 10 mmol each of the monomer and

SO2 in DMSO in the presence of azoisobutyronitrile (AIBN) at 60 oC for 5 h.

bViscosity of 1-0.0625 % polymer solution in salt-free and 0.1 N NaCl at 30

oC was

measured with a Ubbelohde Viscometer (K=0.005718). The average of three

readings (for the time of flow) having standard deviation within 0.2-0.4 seconds are

taken for the viscosity plots.

92

requires C, 41.54; H, 7.24; N, 3.73; S, 8.53 %); max (KBr) 3450, 2983, 2907, 2603, 2575,

1638, 1459, 1404, 1309, 1217, 1128, 1024, 964, 786 and 513 cm-1

. The 13

C NMR

spectrum revealed the presence of two sets of multiplet in a ratio of 73:27, respectively,

attributed to the cis and trans geometric isomers around the five-membered ring structure

of the polymers (Scheme 4−2, Fig. 4.3). P (202 MHz, D2O33.58(s, 1P).

cis-2 trans-2

ab b

a

ClN(CH2)3

(EtO)2P O

S

O

O

[ ] n

ab b

a

ClN(CH2)3

(EtO)2P O

S

O

O

[ ] n

H H

ab b'

a'

ClN(CH2)3

(EtO)2P O

S

O

O

H

[ ] n

A B

cis-5 trans-5

ab b

a

N(CH2)3

(Na+ -O)2P O

S

O

O

[ ] n[ ] n

ab b

a

N(CH2)3

(Na+ -O)2P O

S

O

O

Stereochemistry of the cyclopolymers

Scheme ‎4-2

93

4.2.2.2 Acidic hydrolysis of CPE 2 to PZA 3

CPE 2 (5.5 g, 14.6 mmol) (entry 7, Table 4−1) was hydrolyzed in a solution of

concentrated HCl (40 cm3) and water (30 cm

3) in a closed vessel at 90

ᴼC for 48 h. The

homogeneous mixture was dialyzed against deionized water for 24 h. PZA 3 precipitated

out inside the dialysis bag and dried under vacuum at 55 ᴼC to a constant weight (4.0 g,

97%). The polymer, even though soluble in the reaction mixture in the presence of HCl,

was found to be insoluble in water. The onset of thermal decomposition: (Closed

capillary) turns brown at 250 ᴼ

C and decomposed at 270 ᴼ

C (turned black). (Found: C,

37.9; H, 6.6; N, 4.8; S, 11.0. C9H18NO5PS requires C, 38.16; H, 6.40; N, 4.94; S, 11.32

%); max (KBr) ~3300 (very broad engulfing the CH stretching vibrations), 2917, 2668,

1461, 1409, 1300, 1121, 985, 924, 770, 713, and 513 cm-1

.

The PZA was soluble in HCl to give CPE 4: P (202 MHz, D2O): 29.93 (s) in 6M DCl.

4.2.2.3 Basification of PZA 3 to dianionic polyelectrolyte (DAPE) 5

A sample of PZA 3 (derived from hydrolysis of CPE 2 from entry 7, Table 4−1) (2.5 g,

8.83 mmol) was treated with 2.0 N NaOH (10.6 cm3, 21.2 mmol) and stirred. After the

mixture became homogeneous (10 min), another equivalent of NaOH (4.45 cm3, 8.9

mmol) was added, stirred briefly (1 min), and DAPE 5 was precipitated in methanol.

After filtration and washing with methanol, the white polymer 5 was dried under vacuum

at 55 ᴼC to a constant weight (2.75 g, 95%). The onset of thermal decomposition (Closed

capillary) brown at 270oC become dark brown at 320

ᴼC; (Found: C, 32.8; H, 5.1; N, 4.1;

94

S, 9.5%. C9H16NNa2O5PS requires C, 33.03; H, 4.93; N, 4.28; S, 9.80 %);max (KBr)

3440 (very broad engulfing the CH stretching vibrations), 2940, 2790, 1654, 1458, 1415,

1408, 1302, 1121, 1065, 975, 776, and 556 cm-1

. P (202 MHz, D2O): 22.28.

4.2.2.4 Basification of PZA 3 to ZAPE 6

A mixture of PZA 3 (derived from hydrolysis of CPE 2 from entry 7, Table 4−1) (0.90 g,

3.2 mmol) in water (6 cm3) was neutralized with 1.0 N NaOH (3.25 cm

3, 3.25 mmol).

After the mixture became homogeneous, the solution was then freeze-dried to obtain 6 as

a creamy white powder (0.93 g, 95%). The onset of thermal decomposition: (Closed

capillary) turns brown at 250oC and decomposed at 270

oC (turned black).; (Found: C,

35.1; H, 5.8; N, 4.4; S, 10.2. C9H17NNaO5PS requires C, 35.41; H, 5.61; N, 4.59; S,

10.50%); max (KBr) 3400 (very broad engulfing the CH stretching vibrations), 2944,

1654, 1421, 1306, 1229, 1128, 1069, 974, 778 and 552 cm-1

; P (202 MHz,

D2O21.57(s, 1P)

4.2.2.5 Synthesis and polymerization of zwitterionic Monomer 7 and conversion of the

resultant PZ 8 to PZA 3 and DAPE 5

Zwitterionic monomer 7

was synthesised and polymerized to obtain PZ 8 as

described.Thus SO2 (15 mmol) was absorbed in a solution of the monomer 7 (15 mmol)

in DMSO (3.75 g). The initiator AIBN (80 mg) was then added under N2 and the reaction

mixture was stirred using a magnetic stir-bar at 58 ᴼC for 48 h. The polymer was dialyzed

against deionized water for 48 h. The resulting solution of PZ 8 was freeze-dried to

95

obtain the white polymer (63%), which was stored in a desiccator. PZ 8 on treatment with

one equivalent NaOH was transformed to APE 9. Using procedure as described (vide

supra), PZ 8 was converted to PZA 3 and DAPE 5 by acidic hydrolysis followed by

treatment with two equivalents of NaOH.


The brine concentrations and temperatures encountered in Reverse Osmosis (RO)

desalination process were considered to study the precipitation and inhibition of calcium

sulfate (gypsum) using DAPE 5. A typical analysis of brackish water and reject brine

from RO plant at King Fahd University of Petroleum & Minerals (KFUPM), Dhahran,

Saudi Arabia is given in Table 4−3. The concentration of reject brine (i.e., concentrated

brine) at 70 % recovery (Table 4−3) was denoted as 1CB. Analysis of brine in RO Plant

at KFUPM revealed the concentration of Ca2+

in the brackish feed water and in the reject

brine as 281.2 and 866.7 ppm respectively; while the corresponding concentration of

SO42-

to be 611 and 2,100 ppm. [215]

The evaluation of the newly developed scale inhibitor

was performed in solution containing Ca2+

and SO42-

by 3 times the concentration in the 1

CB. It has been confirmed from solubility data of CaSO4 that 3 CB solutions would be

supersaturated with respect to CaSO4.


and SO42-

ions equals to 6 times the concentrated brine (CB)

were prepared by dissolving the calculated amount of CaCl2 and Na2SO4, respectively, in

deionized water. A solution of 6 CB calcium chloride (60 mL) containing DAPE 5 (20

ppm) was taken in a round bottom flask and heated to 50ºC 1ºC. A preheated (50 ºC)

96

solution of 6 CB sodium sulfate (60 mL) was added quickly to the flask, the content of

which was stirred at 300 rpm using a magnetic stir-bar. The resultant solution containing

10 ppm of DAPE 5 thus becomes 3 CB which is 3×866.7 mg/L i.e. 2600 mg/L in Ca2+

and 3×2100 mg/L i.e. 6300 mg/L in SO42-

.

Conductivity measurements were made at an interval of every 10 seconds initially to

quantify the effectiveness of newly developed antiscalant DAPE 5. The drop in

conductivity indicates the precipitation of CaSO4. Induction time was measured with a

decrease in conductivity when precipitation started. The experiments were continued till

equilibrium is reached. Visual inspection was carefully done to see any turbidity arising

from precipitation.

4.3 RESULTS AND DISCUSSION

4.3.1 Synthesis and Physical Characterization of the Polymers

The results of the polymerization under various conditions are given in Table 9. As

evident from the Table, increasing the initiator concentration led to an increase in the

yield of CPE 2 (entry 1 vs. 2). The highest yield (85%) was obtained using 7 mg of the

initiator and 0.26 g of DMSO per mmol of monomer 1 (entry 5) while polymerization in

the presence of 4 mg of the initiator per mmol of monomer 1 afforded the polymer with

the highest intrinsic viscosity (entry 7). We were gratified to obtain polymers with higher

viscosities and molar masses since degradative chain transfer between macroradical and

97

monomer via the abstraction of allylic or OCH2 proton of the ethoxy group are known to

decrease the molar masses. [216]

Acidic hydrolysis of CPE 2 afforded PZA 3 in excellent yield (97%). PZA 3 on treatment

with 2 and 1 equivalent of NaOH afforded DAPE 5 and ZAPE 6, respectively, in 95%

yields. ZAPE 6 contains an interesting blend of zwitterionic as well as anionic groups in

the same repeating unit.





converted into PZA 3, DAPE 5, and ZAPE 6. Note that both CPE 2 and PZ 8 were

converted to the same DAPE 5 and ZAPE 6 thereby providing us with an opportunity to

compare their solution properties.

Thermogravimetric analysis (TGA) curve of CPE 2 (Fig. 4.1) showed several fractions in

weight loss: the first weight loss of 11.6% in the temperature range 25-125 °C range was

attributed to the loss of moisture, the second loss of 12.5% in the temperature range 125-

200 °C was due to decomposition of the salt to release HCl. A loss of 20.8% in the range

200-321°C was attributed to the loss of SO2. The major loss of 46.3% in the range 321-

600°C was due to the combustion of nitrogenated organic fraction with the release of

CO2, NOx and H2O gases [242]

; the residual mass was found to be 9 % which may be

attributed to Na2O.1.5P2O5.[3]

98

Acidic hydrolysis of CPE 2 afforded PZA 3 in excellent yield (97%). PZA 3 on treatment

with 2 and 1 equivalent of NaOH afforded DAPE 5 and ZAPE 6, respectively, in 95%

yields. ZAPE 6 contains an interesting blend of zwitterionic as well as anionic groups in

the same repeating unit.





converted into PZA 3, DAPE 5, and ZAPE 6. Note that both CPE 2 and PZ 8 were

converted to the same DAPE 5 and ZAPE 6 thereby providing us with an opportunity to

compare their solution properties.

Thermogravimetric analysis (TGA) curve of CPE 2 (Fig. 1) showed several fractions in

weight loss: the first weight loss of 11.6% in the temperature range 25-125 °C range was

attributed to the loss of moisture, the second loss of 12.5% in the temperature range 125-

200 °C was due to decomposition of the salt to release HCl. A loss of 20.8% in the range

200-321°C was attributed to the loss of SO2. The major loss of 46.3% in the range 321-

600°C was due to the combustion of nitrogenated organic fraction with the release of

CO2, NOx and H2O gases [266]

; the residual mass was found to be 9 % which may be

attributed to Na2O.1.5P2O5.[267]

99

Figure ‎4.1 DTA-TGA curve of CPE 2

4.3.1.1 Solubility

The CPE 2 was found to be insoluble in acetone but soluble in methanol. While CPE 2,

DAPE 5 and ZAPE 6 were found to be readily soluble in salt-free water, PZA 3 remained

insoluble. However, in the presence of HCl, PZA 3 is transformed to CPE 4 and becomes

soluble. The critical (minimum) concentration (CSC) of HCl required to promote water

solubility of PZA 3 at 23 C was measured by titration of a 1% w/w polymer solution at

sufficiently high HCl concentration with deionized water. The CSC value, obtained by

visual determination of the first cloud point [206]

, was found to be 0.80 M HCl.

Overwhelming majority of reported polyzwitterions are found to be insoluble in salt-free

100

water, [160,206,215,231,217]

but soluble in the presence of added salts. Particularly, readily

polarizable iodide anions are known to be very effective in neutralizing the cationic

charges in the polymer chain thereby disrupting the zwitterionic interactions and

promoting water-solubility. However, 1% heterogeneous mixture of PZA 3 was found to

be insoluble in any amount of added salts of NaCl, KCl, KBr, KI, and CaCl2. It is worth

mentioning that the corresponding homocounterpart of PZA 3 was also found to be

insoluble in salt-free water, however, a meager 0.03 M NaCl was required to promote its

water-solubility.[239]

The possible rationale behind this difference in solubility behavior

could be attributed to the involvement of SO2 units in strong intra- and interchain H-

bonding involving P(O-)OH and NH+ in PZA 3 in addition to the normal zwitterionic

interactions.

4.3.1.2 Infrared and NMR spectra

The two strong absorptions at 1217 and 1024 cm-1

in the IR spectrum of CPE 2 were

attributed to the stretching frequency of P=O and P-O-C, respectively. For PZA 3, DAPE

5 and ZAPE 6, the corresponding P=O absorption peaks appeared at 985, 1065, and 1069

cm-1

, respectively. The P-O-C peak was missing in the hydrolyzed ester as expected. The

two strong bands at around ~1300 and ~1125 cm-1

were assigned to the asymmetric and

symmetric vibrations of SO2 unit in these polymers.

The absence of any residual alkene proton or carbon signal in the 1H and

13C NMR

spectra of the polymers, displayed in Figs. 4.2and 4.3, suggested the chain transfer

process [164]

for the termination reaction. The proton signals of 2 and 6 are shifted

101

downwards in comparison with that of dianionic 5 as a result of increased

electronegativity of the positive nitrogens in the former polymers (Fig. 4.2). For the

cyclopolymers, the earlier works using 13

C NMR analysis have amply demonstrated the

polymers having the architecture of a five-membered ring-embedded chain.[4,166,218-219]

The ring substituents at C-b can either be in the symmetrical cis (major) or

unsymmetrical trans (minor) dispositions (Scheme 4−2). Integration of the signals

yielded the cis/trans ratio of the ring substituents to be 75:25; similar ratio is observed for

many a Butler’s cyclopolymerization process.[52-55]

Note that the major cis form can exist

in two forms (A and B) in unequal proportion as indicated by the unequal splitting of the

acis or bcis signals (Fig. 4.3).

102

Figure ‎4.2 1H NMR spectrum of monomer 1, CPE 2, DAPE 5 and ZAPE 6 in D2O

The two weak lines of equal intensity for the minor trans-2 which can exist solely in one

form in which case C-a and C-a' or C-b and C-b' becomes nonequivalent (Fig. 4.3). The

spectrum of DAPE 5, however, is much simpler; the substituent at the trivalent nitrogen

undergoes fast inversion and as such looses its stereochemical integrity in the NMR time

103

scale. The splitting of the carbon signals in the cis or trans forms is not observed: Fast

equilibration averages the two cis forms of DAPE 5 (Fig. 4.3, Scheme 4−2).

Figure ‎4.3 13C NMR spectrum of monomer 1, CPE 2, and DAPE 5 in D2O

31P NMR signal for monomer 1, CPE 2, CPE 4, DAPE 5 and ZAPE 6 appeared at 31.4,

33.6, 29.9, 22.3 and 21.6 ppm, respectively (see experimental). The upfield shift of P

104

signal in 5 and 6 is attributed to the higher electron density around P as a result of the

negatively charged oxygens.

4.3.1.3 Viscosity measurements

The Huggins viscosity plots for CPE 2, DAPE 5 and ZAPE 6 (having identical degree of

polymerization) in salt-free water remain concave upwards like any polyelectrolytes (Fig.

4.4). In the high dilution regime, the reduced viscosities fall off rapidly with the decrease

in concentration. CPE 2, represented in the condensed form as R3NH+

is actively

involved in the equilibration represented by Eq.1 to form an increasing amount of the

neutral form R3N:. The placement of neutral form in the polymer chain reduces the

cationic charges thereby reducing repulsion and viscosity. Likewise, DAPE 5 and ZAPE

6 through involvement in the equilibrations (Eqs. 2 and 3) reduces overall charge

densities in the polymer chain and viscosity

105

0

5

10

15

20

25

30

35

40

0 0.2 0.4 0.6 0.8 1 1.2

C (g/dL)

s

p/C

(

dL

/g)

Figure 4.

In salt-free water

■ CPE 2

□‎‎ZAPE 6

▲‎DAPE 5

CPE 2: R3NH+

+ H2O ⇋ R3N: + H3O+

(1)

DAPE 5: R2NA(O)22-

+ H2O ⇋ R2NA(OH)O- + H3O

+ (2)

ZAPE 6: R2NH+A(O)2

2- + H2O ⇋ R2NH

+A(OH)O

- + H3O

+ (3)

. The sequence of decreasing reduced viscosity in salt-free water was found to be:

CPE 2 > ZAPE 6 > DAPE 5

Figure ‎4.4 The viscosity behavior of CPE 2, DAPE 5, and ZAPE 6 (from entry 7, Table 4−1) in salt-free

water 30oC using an Ubbelohde Viscometer

106

Dianionic 5 is unexpectedly found to have lower viscosity values than

zwitterionic/anionic 6 as a result of the former having neutral nitrogens in the polymer

backbone. Note that the increased distance between the negative oxygens in the

neighboring repeating units in DAPE 5 leads to less effective repulsion. It may be

possible that the less effective neutralization of the positive nitrogens by negatively

charged oxygens in ZAPE 5 leaves behind a net positive charge whose shorter distance

between the neighboring repeating units leads to repulsion and higher viscosity.

Table ‎4-2 Comparative viscositiesa of CPE 2, DAPE 5, ZAPE 6, PZ 8 and APE 9

polymer NaCl

(N) []

(dL/g)

Correlation

coefficient

(R2)

CPE 2 (entry 7, Table 9) 0.1 1.27 0.9990

DAPE 5b

0.1 1.67 0.9983

ZAPE 6b

0.1 1.96 0.9966

0.5 1.00 0.9936

1.0 0.831 0.9995

CPE 2 (entry 6, Table 9) 0.1 0.432 0.9903

DAPE 5c

0.1 0.915 0.9989

ZAPE 6c

0.1 0.945 0.9993

PZ 8

0 0.0545 0.9979

0.1 0.0678 0.9900

DAPE 5d

0.1 0.168 0.9990

APE 9d

0.1 0.146 0.9928 aViscosity of 1-0.0625 % salt-added polymer solution at 30 oC was measured with a

Ubbelohde Viscometer (K=0.005718). The average of three readings (for the time of flow)

having standard deviation within 0.2-0.4 seconds are taken for the viscosity plots. bderived via CPE 2 (entry 7, Table 9) . cderived via CPE 2 (entry 6, Table 9) . dderived via PZ 8.

107

Table ‎4-3 Analysis of feed water and reject brine showing major species in RO Plant at KFUPM, Dhahran.

Item Brackish Watera

Cations Feed (mg/l) Reject Brine at

70 % recovery

(mg/l)

Al3+

< 1.0 < 1.0

Ba2+

< 0.05 0.2

Ca2+

281.2 866.7

Cu2+

< 0.05 0.2

Fe2+

< 0.1 < 0.1

K+ 32.0 88.9

Mg2+

88.9 275.4

Mn2+

< 0.05 < 0.05

Na+ 617.2 1,653

P3+

< 0.1 0.88

Sr2+

3.98 12.1

Zn2+

< 0.05 0.07

Anions

Br- 5.9 15.8

Cl- 1,410 3,930

F- < 0.4 < 0.4

HCO3- 241 683

NO3- 7.7 19.1

PO43-

< 0.6 < 0.6

SO42-

611 2,100

Others

SiO2 29.8 81.4

TDS 3,329 9,730

I (moles/l) 0.06995 0.2087

pH 6.8 7.2

aSource: Dhahran brackish water, Butt et al., 1995(Ref.45).

Viscosity plots became linear in the presence of 0.1 N NaCl, and the sequence of

decreasing intrinsic viscosity was found to be (Fig. 4.5, Table 4−2):

ZAPE 6 > DAPE 5 > CPE 2

108

0.05

0.07

0.09

0.11

0.13

0.15

0.17

0.00 0.20 0.40 0.60 0.80 1.00 1.20

C (g/dL)

hsp/C

(d

L/g

)

■ DAPE 5

□ APE 9

▲ PZ 8

∆ PZ 8

0.1 N NaCl

Salt-free water

(a)

(b)

(c)

(d)

Derived from

PZ 8

Figure 6.

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

0 0.2 0.4 0.6 0.8 1 1.2

C (g/dL)

s

p/C

(d

L/g

)

(a)

(b)

(c)

(d)

(e)

(NaCl)

□ CPE 2 0.1 N

(Entry 7, Table 1)

Derived from CPE 2

■ ZAPE 6 0.1 N

● DAPE 5 0.1 N

▲ ZAPE 6 0.5 N

∆ ZAPE 6 1.0 N

Figure 5.

Figure ‎4.6 The viscosity behavior of CPE 2, DAPE 5, and ZAPE 6 (from entry 7, Table 4−1) in the presence of

NaCl at 30ᴼC using an Ubbelohde Viscometer

Figure ‎4.5 The viscosity behavior of PZ 8, DAPE 5 (via PZ 8), and APE 9 (via PZ 8) in 0.1 N NaCl at

30ᴼC using an Ubbelohde Viscometer.

109

Hydration shell of Na+ is generally fairly large; hence the distance of closest approach is

not sufficient to effectively neutralize the charge on the pendent phosphonate anions in 6

whereas the strongly binding Cl- ions do effectively shield the positive nitrogens in CPE

2. The dianionic DAPE 5 remained less viscous than ZAPE 6 for the reason discussed

above. The decrease and increase of intrinsic viscosity in the presence of an added salt is

a demonstration of “polyelectrolyte” and “anti-polyelectrolyte” behavior of a

polyelectrolyte (cationic or anionic) and a polyzwitterion, respectively.

Note that the

intrinsic viscosity of ZAPE 6 in 0.1 N, 0.5 N, and 1.0 N NaCl was found to be 1.96, 1.00,

and 0.831 dL/g, respectively. ZAPE 6 has dual groups of zwitterion and anion; it is the

anionic portion that dictates the viscosity behavior (Fig. 4.6). The presence of NaCl leads

to contraction and expansion of the polymer chains of a polyelectrolyte and

polyzwitterion, respectively. The “polyelectrolyte” effect of the anionic portion in ZAPE

6 dictates the behavior thereby leading to the decreasing intrinsic viscosity values in the

presence of increasing concentrations of NaCl.

Unlike polyelectrolytes, the viscosity plots for zwitterionic 8 in the absence or

presence of added salt (NaCl) remain linear (Fig. 4.6); the intrinsic viscosities in salt-

free and 0.1 N NaCl were found to be 0.0545 and 0.0678 dL/g, respectively. An increase

in the intrinsic viscosity in the presence of NaCl is a demonstration of the “anti-

polyelectrolyte” behavior of the PZ 8. As discussed earlier, the Cl- ions shield the positive

nitrogens more effectively than the shielding of phophonate anions by the hydrated Na+

ions. As a result, the zwitterionic moiety is left with a net negative charge that leads to

repulsion hence expansion of the polymer chains. While CPE 2, DAPE 5, and ZAPE 6

110

(derived from CPE 2) have intrinsic viscosity values of 1.27, 1.67, and 1.96 dL/g in 0.1 N

NaCl, respectively, the corresponding values for PZ 8, DAPE 5, and APE 9 (derived from

PZ 8) are determined to be 0.0678, 0.168, and 0.146 dL/g in 0.1 N NaCl (Table 4−2).

Note that transformation of PZ 8 to DAPE 5 leads to higher magnitude of viscosity

increment than that observed for the corresponding transformation of CPE 2 to DAPE 5.

This indicates that PZ 8 has much lower [] due to having zwitterionic groups that leads

to contraction of the polymer chains.

The solution behavior of ionic polymers presented above can be described

mathematically [239,220-222]

,in terms of electrostatic excluded volume v*:

where IB is the Bjerrum length, f is the total fraction of charged monomers, f is the

charge imbalance, and S is the Debye-Huckel screening parameter. The first term of eq 4

describes the screening of the attractive polyampholytic interactions among opposite

charges, while the screening of the Coulombic repulsive interactions among excess

charges is rationalized by the second term. Since the f = 0 for the electroneutral (±)

PZA 3 and (±) PZ 8, the second term of eq 4 vanishes; the solution behavior must then be

described by the first term describing the screening of the attractive zwitterionic

interactions. The negative electrostatic excluded volume (v*) thus indicates contraction to

a collapsed polymer chain which leads to PZA 3 being water-insoluble and PZ 8 having

)4(f4π)π(f

- *v2

2

B

2

B

SS

II

111

very low [] (Table 4−2). The water-insolubilty (±) PZA 3 has already been discussed

(vide supra), while unexpected water-solubility of (±) PZ 8 may be attributed to the steric

encumbrance of the ethoxy group which restricts the close encounter of the opposite

charges for the manifestation of intragroup, intra- and interchain attractive zwitterionic

interactions. For (± -) ZAPE 6f = 0.33; the charge imbalance seems to make the

second term more dominant and thus outweighs the contribution by the first term. The

resultant positive electrostatic excluded volume (v*) leads to expanded polymer chain as

ascertained by the higher viscosity values for ZAPE 6 over PZ 8 (Table 4−2) even though

both have identical degree of polymerization. As the salt (NaCl) concentration increases

(from 0 to 0.1 N), for electroneutral (±) PZ 8 the magnitude of the first and second term

increases and decreases, respectively. This is attributed to the more effective screening of

the positive nitrogens by Cl- ions than the screening of the negative oxygens by the Na

+

(vide supra). The unequal screening of the charges by NaCl thus makes the PZ 8 overall

negative; hence the contribution of the second term leads to the expansion of the polymer

chain and increase of the [] (Table 4−2). For ZAPE 6, however, the negative charge

imbalance (f) of 0.33 is screened by the Na+ ions and as a result the [] values

decreases with the increase in salt concentrations (Table 4−2).

4.3.2 Effectiveness of DAPE 5 as an antiscalant


CaCO3, CaSO4, Mg(OH)2), corrosion products, polymeric silica and suspended matter.

Davey [205] presented an excellent review on the inhibition of scaling by antiscalants by

their ability to sequestrate polyvalent cations so as to alter the crystal morphology at the

112

time of nucleation and subsequently inhibit growth rate of crystal formation. [1]

Commonly used anionic antiscalants such as condensed poly(phosphate)s,

organophosphates, and polyelectrolytes [223]

help prevent scale formation by sequestering

the cations. Extraordinary chelating compounds containing aminomethylphosphonic acid

group are able to form polymer-heavy metal ion complexes from waste water.[233,235]

For the current work, the precipitation behavior of a supersaturated solution of CaSO4

containing 2600 ppm of Ca2+

and 6300 ppm of SO42-

in the absence and presence of 10

ppm of DAPE 5 was investigated. Conductivity measurements were made at an interval

of every 10 seconds initially to quantify the effectiveness of the newly developed

antiscalant DAPE 5. Induction time was measured when precipitation started which is

observed by drop in conductivity. It was found that conductivity did not decrease for

about 1800 minutes with 100 % scale inhibition in the presence of 10 ppm of DAPE 5.

After that conductivity dropped from 17.35 mS/cm to 15.11 mS/cm as shown in Fig.

4.7b. Note that in the absence of antiscalant DAPE 5, the spontaneous precipitation

started within 500 seconds as indicated by the drop in conductivity (Fig. 4.7a: Blank).

The results indicate that the synthesized additive is very effective against precipitation of

gypsum at 50 °C and hence, suitable for use in inhibiting calcium sulfate precipitation in

RO plants. It is worth mentioning that the corresponding homocounterpart of DAPE 5 at

a concentration of 10 ppm was also found to be an effective antiscalant with a scale

inhibition of 95.6 % after the elapse of 1800 min.[239]

The copolymer DAPE 5 (the current

polymer) performed better thus ascertaining the beneficial effect of the presence of the

113

backbone stiffening SO2 units not only as an antiscalant but also in improving yield of its

formation as well as enhancement of solution viscosities.

Figure ‎4.7 Precipitation behavior of supersaturated solution of CaSO4 in (a) without DAPE 5 (b) 10ppm

DAPE 5.

114

4.4 Conclusions

Using Butler’s cyclopolymerization process, we have synthesized a new cationic

polyelectrolyte (CPE) 2, a copolymer of 1-alt-SO2, containing a pendant having three-

carbon spacer separating the diethylphosphonate and NH+

groups. CPE 2 was then

readily converted by acidic hydrolysis of the phophonate esters into pH-responsive PZA

3, DAPE 5 and ZAPE 6. The solution properties of the polymers were then correlated to

the type of charges and their densities on the polymer chain. Evaluation of antiscaling

properties revealed that DAPE 5 at a meager concentration of 10 ppm is very effective in

inhibiting the formation of calcium sulfate scale, and as such it can be used effectively as

an antiscalant additive in Reverse Osmosis plant.

115

5 CHAPTER 5: HEAVY METAL IONS EXTRACTION USING A

NOVEL POLYPHOSPHONATE RESIN

Shaikh A. Ali and Izzat W. Kazi

5.1 Introduction

Contamination from heavy metal ions has attracted tremendous attention owing to their negative

effects on the environment. These toxic pollutants are nonbiodegradable and can accumulate in the

human body causing a variety of diseases and disorders [224-225]

. Heavy metals such as lead and

copper, widely used in batteries, mining and tannery, can cause anemia, insomnia, renal damages,

central nervous system damage and dysfunction of the immune system [18- 20]

. A variety of

techniques like adsorption, precipitation, dialysis, ion exchange, reverse osmosis and extraction,

have been reported for the removal of metal contaminants. One of the most attractive among these

techniques is presumably the adsorption process due to the availability of different types of efficient

adsorbents [21- 24]

. Inorganic/organic polymer hybrid adsorbents have been widely investigated, and

their efficiency of metal ion removal has been attributed to the formation of a stronger chemical

bonding between Mn+

and, for instance, amine motifs in the hybrid materials [226-230]

. Recently

researchers have focused on the synthesis of zwitterionic cross-linked inorganic/organic hybrid

materials in removing heavy metal ions via electrostatic effects [231-235]

.

A titania-phosphonate hybrid porous material has been found to have a large capacity for selective

adsorption of Cd(II) ions [236]

. Considerable attention has been given to synthesize chelating agents

containing aminomethylphosphonate motifs owing to its extraordinary chelating properties in

116

extracting heavy metal ions from waste water [237]

. In this work, a novel cross-linked polymer

containing aminopropylphosphonate motifs has been synthesized and tested for its efficiency as an

adsorbent for the removal of heavy metal ions like Pb(II) and Cu(II) ions from aqueous solutions.

Desorption of the metal ions from the cross-linked polymer has also been investigated for the

recovery of the metal ions and recycling of the polymer.

5.2 Experimental


Perkin Elmer Elemental Analyzer Series 11 Model 2400 was used for Elemental analysis . while IR

analysis were performed on Thermo scientific FTIR spectrometer. 1H spectra were scanned in D2O

at +25 °C (using HOD peak at 4.65) on a JEOL LA 500 MHz spectrometer. A TESCAN LYRA 3

(Czech Republic) Equipped with Oxford, energy-dispersive X-ray spectroscopy (EDX) detector

model X-Max were used for Scanning electron microscopy images and EDX spectra.

5.2.2 Materials

2,2′-Azoisobutyronitrile (AIBN) from Fluka AG was purified by crystallization from a chloroform-

ethanol mixture. Dimethylsulfoxide (DMSO) was dried over calcium hydride overnight and then

distilled at a boiling point of 64-65C (4 mmHg).. All solvents used were of analytical grade. All

glassware was cleaned with deionized water.

http://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy

117

5.2.3 Synthesis of monomers

5.2.3.1 Hydrolysis of Monomer 1 to Diallylaminopropylphosphonic acid 2

Hydrolysis has been done by heating 20g; 72.6 mmol of monomer 1 in a round bottomed flask with

85 mL of 41% v/v HCl uder reflux at 105oC for 72 h. Nitrogen gas was purged at 100

oC to get rid

of excess HCl and water. The product was freeze dried to obtain a viscous liquid of

Diallylaminopropylphosphonic acid 2. A 1H NMR spectrum of a mixture containing a known

mass of this crude product and a known mass of ethanol in D2O revealed the purity of the product.

Integration of the signal of CH2P- proton of 2 at 3.11 versus CH2O of ethanol at 3.40 helped us to

determine the purity of the crude product. The crude product of 122 g contained 0.42 mol of 2,

thereby implying 84 % yield for the reaction. The crude sample of 0.290 g was found have 1 mmol

(0.191 g) of 2 (i.e. the crude product contained 66 %w/w monomer 2; the rest of the materials may

include HCl, H2O etc. The 1H NMR spectrum was very clean and was free of any undesired

products. The monomer 2 was used in the subsequent polymerization without any further

purification.

5.2.4 1,1,4,4-tetraallylpiperazinium dichloride 3

Monomer 3, a cross-linker, was prepared as described [238]

118

5.2.5 General Procedure for the Terpolymerization of 2 and 3 with Sulfur Dioxide

Polymerization was carried out by dissolving monomer 2 (36.7 mmol; 8.04 g) and crosslinker 3

(4.07 mmol; 1.30 g) in DMSO (12.22 g) in a 50 mL round bottomed flask. SO2 was absorbed by

gentle blowing it over the stirred surface of the solution . The reaction was initiated by adding

AIBN (272 mg) in a continuously stirred mixture at 65 °C under N2 for 16 h. The magnetic stir-bar

was stopped moving after 5h and the reaction mixture became a transparent swelled gel. At the end

of the elapsed time, the swelled gel of the cross-linked polyzwitterionic acid (CPZA) 4 was soaked

in water (12 h) with replacement of water several times. The swelled gel was then poured onto

acetone. The resin was filtered and dried at 70 °C under vacuum to a constant weight (5.8 g)

The onset of thermal decomposition (Closed capillary): The resin was stable up to 350 ᴼC, thereafter

slight decoloration to pale yellow; (Found: C, 50.3; H, 8.5; N, 6.4; S, 10.2 momomer 2 C7H13NO3P

(90 mol%) and monomer 3 C16H28Cl2N2 (10 mol%) requires C, 50.40; H, 8.34; N, 6.63); max (KBr)

3734, 3381, 2291, 1662, 1460, 1414, 1305, 1127, 1047, 973, 883, 781, 618, 563, and 438 cm-1

.

5.2.5.1 Basification of CPZA 4 to cross-linked dianionic polyelectrolyte (CDAPE) 5

CPZA 4 (6.33 g, ~ 22 mmol) was treated with NaOH (2.4 g, 60 mmol) in water (200 cm3) stirred at

room temperature for 1 h. The resulting gel then poured into another flask containing (200 mL

Methanol + 800 mg NaOH) solution. The polymer then filtered and washed several times with

Methanol. A turbid filtrate obtained, which on addition of acetone gave white fluffy precipitates.

119

The precipitates were filtered again. The residue was dried under vacuum at 70 °C to a constant

weight (6.04 g).

The onset of thermal decomposition (closed capillary): The resin was stable up to 350 ᴼC, thereafter

slight discoloration to pale yellow.

5.2.6 Sample characterization

FT-IR spectra have been recorded on a Perkin Elmer 16F PC FTIR spectrometer in the region of

4000-400 cm-1

. Ion exchange capacity (IEC) was determined by titremetric analysis method [Eq.

(1)]. The dried and weighed polymer (100 mg) was immersed in 50 ml of 0.1 M hydrochloric acid

for 24 h. The ion exchange capacity was determined from the decrease in acidity by titration with

0.1 M NaOH solution.

)1(W

mmolmmolIEC

fi

Where mmoli and mmolf are the initial and final amount of HCl in mmol, respectively. W is the

weight of the polymer in g [239]

.

5.2.7 Adsorption experiments

The adsorption properties of the cross-linked polymer CDAPE 5 for Pb2+

and Cu2+

ions were

determined by titration; the procedure for Pb2+

adsorption was as follow: A mixture of CDAPE 5

(50 mg) in 20 ml of 0.1 M Pb(NO3)2 in buffer solutions of different pH’s was stirred using a

120

magnetic stir-bar for 24 h. The resin was filtered and carefully washed with respective buffer

solution. The combined filtrate was titrated with 0.1 M EDTA solution using xylenol orange as

indicator to find out the amount of Pb2+

remained.

The adsorption capacity ( 2Pbq ) can be calculated using Eq. (2):

)2(/)( 0

2 gmmolW

VCCq

f

Pb

Where Co and Cf are the initial and final concentration of Pb2+

ions, respectively, W is the weight of

the polymer in gram and V is the volume of the solution in milliliter.

Similar procedure was conducted for adsorption of Cu+2

ions using a 0.1 M Cu(NO3)2

solution. The amount of Cu2+

ions left in the solution was determined by iodometric titration using

excess KI and 0.1 M Na2S2O3 solution [258,272,273]

Adsorption kinetic studies were carried out by stirring 0.1 M metal ion (M+2

) solution (100

mL) in a favored pH buffer with resin (250 mg) at different temperatures and determine the metal

ion concentration by taking a small amount of filtered aliquots at various time intervals. Adsorption

isotherms were constructed by determining the adsorption capacities of the resin at different metal

ion concentration ranging from 0.02 M to 0.1 M at ambient temperature. Thermodynamic

parameters G, H and S were calculated using data from experiments carried out at different

temperatures.

121


5.3.1 Synthesis of cross-linked polymer 4 and 5

Zwitterionic acid (ZA) monomer diallylaminopropylphosphonic acid 2 was synthesized by the

extensive acid hydrolysis of monomer 1. Butler’s cyclopolymerization of 2 has been reported to give

the cyclopolymer polyzwitterionic acid 5 (Scheme 5−1) [278]

. Cyclopolymerization of a variety of

N,N-diallyl ammonium salts, in fact, has led to the synthesis of an array of scientifically and

technologically important water-soluble cationic polyelectrolytes [240-245]

. The polymer-architecture

having five-membered cyclic units embedded in the backbone has been recognized as the eighth

major structural type of synthetic polymers. Over 33 million pounds of

122

Cl

Cl

OH

AIBN

DMSO

SO2

NaOHCrosslinked polyzwitterion (CPZA)

Crosslinked dianionic polyelectrolyte

(CDAPE)

2Cationic monomer

p q[ ] [ ]

N(CH2)3

P OO

O

S

O

O

N

NN

(CH2)3

P OO

O

S

O

O

Na

Na Na

NaOH

N(CH2)3

(EtO)2P O

HCl

1050C

1 3

4

5

NH (CH2)3

P OO

HO

NH (CH2)3

P OO

HO

S

O

O

p q[ ] [ ]

N

NN

H (CH2)3

P OO

HO

S

O

O

N

N Cl

Cl

Scheme ‎5-1

123

poly(diallyldimethylammonium chloride) are sold annually for water treatment and 2 million pounds

are used for personal care formulation [246]

ZA 1 underwent cyclocopolymerization in the presence of 10 mol% of cross-linker 1,1,4,4-

tetraallylpiperazinium dichloride 3 in DMSO in the presence of initiator AIBN to give the novel

cross-linked polyzwitterionic acid (CPZA) 4 in very good yields (Scheme 5−1). The results of the

polymerization under various conditions are given in Table 5−1. The yield is almost doubled by

doubling the initiator (entries 3 and 4 vs. 5 and 6). The higher concentration of the initiator is

required since the presence of diallyl moiety could result in the extensive degradative chain transfer

between the polymer radical and monomer [247]

. To the best of our knowledge, the synthesis of

CPZA 4 represents the first example of a cross-linked polymer (containing important

aminopropylphophonate motifs) by cyclopolymerization protocol.

CPZA 4, a swelled gel in water, shrank on soaking in acetone owing to the removal of water.

Basification with excess NaOH, led to cross-linked dianionic polyelectrolyte (CDAPE) 5 in

excellent yield. Elemental analyses revealed the incorporation of the monomers 2 and 3 in nearly

90:10 mol ratio, the same as the feed ratio. The multiple bands in the IR spectra in the region of

900–1150 cm−1

are attributed to the phosphonate P–O vibrations (Fig. 5.1C) [248-249]

124

Figure ‎5.1 IR spectra of (a) Cross-linked polyanion 5 loaded with Cu2+ (b) Cross-linked polyanion 5 loaded with

Pb2+.and (c) Cross-linked polyanion 5

5.3.2 Adsorption properties of CDAPE 5

The high ion exchange capacity (IEC) of the resin CDAPE 5, 5.02 mmol/g, ascertains the excellent

adsorption ability for metal ions (M2+

). The presence of chelating ligands –N: and phosphonate

motifs –P(=O)O22-

expected to be responsible for this chemical adsorption. The two strong bands at

972 and 1047 cm −1

in the IR spectrum of the resin 5 are attributed to the phosphonate P−O

vibrations,[250-251]

and the absorptions at 1127 and 1304 cm−1

were assigned to the asymmetric and

symmetric vibrations of SO2 unit (Figure 1C). The C−N absorption was found near 1460 cm−1

. The

peaks around 1660 cm−1

were determined the H−O−H bending vibration. The appearances of new

strong bands at 1382 (Fig. 1A) and 1383 cm-1

(Fig. 1 B) were attributed to the presence of ionic

nitrate group since the adsorption process was carried out in the presence of metal nitrates [35]

. The

Wavenumbers

1800 1600 1400 1200 1000 800 600 400

Tra

nsm

itta

nce

0

50

100

3420.1

4

2924.5

2

2360.4

42342.1

2

1636.3

1383.6

7

1300.7

5

1125.2

6

1006.6

6957.4

84

824.4

2772.3

51

711.6

04

668.2

14

505.2

58

Kazi_Pb_Co

a

b

c

a

b

c

a

b

c

a

b

c

125

presence of these strong bands thereby implies the ability of the resin to act also as an anion

exchanger at pH 4 for Pb2+

and pH 5 for Cu2+

. Note that absorption band attributed to the nitrate ion

is absent in the unloaded resin (Fig. 1C).

A comparison of the IR spectra of CDAPE 5 and Cu2+

and Pb2+

loaded CDAPE 5 (Figure 5.1)

reveals strong perturbations of the P−O peaks, implying a direct bond between metal ions and the

phosphonate group. The spectra revealed the increase in the intensity and broadness of the

phosphonate P−O vibrations as a result of the adsorption of the metal ions.[252]

5.3.3 Adsorption kinetics

The plots of adsorption capacity versus temperature for metal ions are shown in Fig 5.2 . It was

found that the adsorption equilibrium for Cu2+

and Pb2+

ions by CDAPE 5 reached in about 1.5h Fig

5.2.

Fig. 5.3. displays the maximum adsorption at three different temperatures Lagergren adsorption

kinetic model has been reported as a suitable tool to investigate the adsorption

126

Figure ‎5.2 Adsorption kinetic curves of Cu2+ and Pb2+ in 0.1 M solution at their optimum pH 4 and 5 respectively at a)

295 K b) 308 K c) 323 K.

Figure ‎5.3 Effect of temperature on adsorption capacity of CDAPE 5

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 1 2 3 4 5 6 7 8 9

qM

+2

(mm

ol.

g-1)

Time (h)

Cu_295 K

Cu_308 K

Cu_323 K

Pb_295 K

Pb_308 K

Pb_323 K

y = 0.0065x + 2.0102 R² = 0.9962

y = 0.0191x - 3.4974 R² = 0.9995

1.50

2.00

2.50

3.00

3.50

4.00

4.50

290 300 310 320 330

qM

+2

(m

mol.

g-1

)

Temperature (K)

Cu

Pb

127

properties of a polymer [258]

. The following equations express the linear first and second-order

kinetic equations (Eqs. 3 and 4) for the Lagergren model, respectively:

)3(303.2

log)(log 1tkqqq ete

)4(1

2

2 eet q

t

qkq

t

Where k1 and k2 are the first-order and second-order rate constant, respectively; qt and qe are the

adsorption capacities of the metal ions at time t and at equilibrium, respectively. Although Pb2+

and

Cu2+

both gave regression value (R2) above 0.9 for the first-order Lagergren kinetic model, but there

is a vast difference between the experimental adsorption capacity and the calculated adsorption

capacity so the graph representing the kinetic model has not been displayed, while the Cu2+

and Pb2+

were well fitted in the second-order Lagergren kinetic model (Fig. 5.3) with very close experimental

adsorption capacity and the calculated adsorption capacity (Table 5-1).

128

Figure ‎5.4 Lagergren second-order kinetic model for adsorption of Cu2+ and Pb2+ on CDAPE5 at a) 295 K b) 308 K

c) 323 K.

The values represented in Table 5−2 show that the rate constant (k2) for the removal of Pb2+

is

higher than for Cu2+

; however, CDAPE 5 adsorbs larger amount of Cu2+

at the longer periods of

time (Fig.5. 9, Table 5-1). The adsorption capacity of Cu2+

is thus found to be larger than that of

Pb2+

. The rationale for such difference could be attributed to the lower effective ionic radii of Pb2+

(4.5 Å) than that of Cu2+

(6 Å) and differences in the affinity of phosphonate motifs in the resin for

y = 0.5267x + 0.1608 R² = 0.9974

y = 0.4454x + 0.0735 R² = 0.9938

y = 0.5468x + 0.0563 R² = 0.9995

y = 0.2408x + 0.031 R² = 0.9987

y = 0.2315x + 0.0279 R² = 0.9995

y = 0.2269x + 0.0251 R² = 0.9989

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 2 4 6 8

t/q

t

Time (h)

Pb_295 K

Pb_308 K

Pb_323 K

Cu_295 K

Cu_308 K

Cu_323 K

129

the metal ions [293]

. The results revealed that the resin is an efficient adsorbent for removing both

lead and copper ions from aqueous solutions.

130

Table ‎5-1 Lagergren second–order kinetic model parameters for Cu2+ and Pb2+ adsorption

Metal ion Temperature qe_Calc k2 ha qe_Exp R

2

K (mmol g-1

) (h g mmol-1

) (h g mmol-1

) (mmol g-1

)

Cu+2

295 4.167 1.858 32.26 4.002 0.998

308 4.329 1.976 37.04 4.188 0.999

323 4.425 2.128 41.67 4.275 0.998

pb+2

295 1.901 1.729 6.250 1.879 0.997

308 2.247 2.713 13.70 2.274 0.993

323 1.832 5.324 17.86 1.779 0.999

aInitial adsorption rate h = k2 qe

2.

5.3.4 Effect of initial concentration on the adsorption of copper and lead ions

The adsorption capacity of CDAPE 5 increases with increasing concentrations of lead and copper

ions (Fig 5.5). The Langmuir isotherm is based on the assumptions that on structurally homogeneous

adsorbent, all adsorption sites are energetically equivalent and

Figure ‎5.5 The effect of initial concentration on the adsorption capacity of CAPE 5 at pH4 for Pb+2 and pH 5 for Cu+2

24 h at 25 ᴼC

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0 0.05 0.1 0.15

qM

+2

(mm

ol.

g-1)

C0 (mol.dm-3)

Cu

Pb

131

Figure ‎5.6 Langmuir isotherm of the adsorption of Cu2+ and Pb2+ ions on CAPE 5

identical as well as the intermolecular force decreases rapidly with distance. So it follows the

mechanism as a monolayer adsorption on the surface of the polymer. The Langmuir constants and

adsorption capacities can easily be calculated by linearized Langmuir isotherm equation (5) as

follows

)5(1

bQQ

C

q

C

mm

e

e

e

y = 0.2612x + 0.0255 R² = 0.9909

R² = 0.9899 y = 0.0992x + 0.009

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.00 0.05 0.10 0.15

Ce/

qe

(g

.mL

-1 )

Ce (mol.dm-3)

Langmuir Isotherm

Pb

Cu

132

where qe is millimoles of metal adsorbed per gram of the CDAPE 5; Ce is the metal residual

concentration in solution at equilibrium, Qm is the maximum specific uptake corresponding to the

site saturation and b is the ratio of adsorption and desorption rates, the Langmuir constant [253]

. Fig.

5.6 represents the plot of Ce/qe versus Ce. On the other hand, Freundlich isotherm model, , describe

heterogeneous adsorption systems with uniform energy; Eqs. 6 and 7 express the model:

)7(log1

loglog efe Cn

kq

Where qe and Ce are the equilibrium concentrations of metal ions on the adsorbed and the liquid

phase, respectively; kf and n represent the Freundlich constants, which can be calculated from the

slope and intercept of Fig. 5.7 which shows the plot of log qe versus log Ce.

)6(/1 n

efe Ckq

133

Figure ‎5.7 Freundlich isotherm of the adsorption of Cu2+ and Pb2+ ions on CAPE 5

The Temkin isotherm equation suggests that owing to adsorbent-adsorbate interactions, the heat of

adsorption of molecules in layer decreases linearly with coverage, and the adsorption is

characterized by a uniform distribution of the bonding energies (Temkin, 1940). The Temkin

isotherm can be expressed by the following equation:

………………….(8)

and can be linearized as:

…………..(9)

R² = 0.9933 y = 0.7054x + 1.4591

y = 0.6926x + 0.9992 R² = 0.9942

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

-2.00 -1.80 -1.60 -1.40 -1.20 -1.00 -0.80

log

qe

log ce

Fraundlich Isotherm Cu

Pb

134

where B corresponds to the adsorption potential of the adsorbent (KJ/mol), A is the Temkin isotherm

constant (L/g). A plot of qe versus lnCe (Fig. 5.8) is used to calculate the Temkin isotherm constants

A and B.

Fig. 5.6, 5.7 and 5.8 illustrate that the adsorption of both Cu2+

ad Pb2+

ions by CDAPE fitted well the

Langmuir, Freundlich and Temkin isotherm models, thereby implying that the adsorption may occur

as a monolayer as well as a heterogeneous surface adsorption. The Langmuir, Freundlich and

Temkin isotherm model constants are given in Table 5-2.

At a pH between 4 to 5, the zwitterionic phophonate motifs [i.e. NH+….

P(=O)(OH)O-] in CPZA 4

may partially change to zwitterionic/anionic motifs [i.e. NH+….

P(=O)(O-)2] which can influence the

adsorption of metal ions on the resin surface by electrostatic adsorption that follows Langmuir

adsorption model.

135

Figure ‎5.8 Temkin isotherm of the adsorption of Cu2+ and Pb2+ ions on CAPE 5

For the Langmuir isotherm model, separation factor or equilibrium parameter (RL) can be used to

describe the favorability of adsorption on the polymer surface by Eq. (10) [272]

:

)10()1(

1

0bCRL

Where Co is the initial M2+

concentration and b is the Langmuir equilibrium constant. A favorable

adsorption is indicated when the RL value is between 0 < RL <1, whereas the RL values outside the

range describes an unfavorable adsorption. The RL values for the adsorption of both metal ions are

given in Table 5-3, which reveals that RL values fall in the preferred region (0 < RL < 1). The results

thus declare that CDAPE 5 is a promising adsorbent for the removal of heavy metal ions in aqueous

solutions.

R² = 0.9878

y = 2.111x + 9.6681

y = 0.7816x + 3.6865 R² = 0.9885

0.00

1.00

2.00

3.00

4.00

5.00

6.00

-4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0

qe

(m

mo

l.g-1

)

ln Ce

TEMKIN Isotherm

Cu

Pb

136

Table ‎5-2 Langmuir Freundlich and Temkin isotherm model constants for Cu2+and Pb2+ adsorption

Temkin isotherm model

Table ‎5-3 The RL values based on the Langmuir isotherm model

Co

(mol dm-3

)

RL value

Pb2+

Cu2+

0.02 0.8273 0.8197

0.04 0.7054 0.6944

0.06 0.6149 0.6024

0.08 0.5449 0.5319

0.1 0.4892 0.4762

Langmuir isotherm model

Entry No

Metal ion Qm

(mmol g-1

) b

(dm3 mmol

-1)

R2

1

Pb+2

3.831 10.44 0.992

2

Cu+2

10.101 11.00 0.996

Freundlich isotherm model

Entry No Metal ion n kf R2

1 Pb+2

1.445 9.977 0.994

2 Cu+2

1.418 28.774 0.993

Entry No Metal ion B A R2

1 pb+2

0.781 112 0.988

2 Cu+2

2.111 97 0.987

137

5.3.5 Effect of pH and temperature on adsorption.

Adsorption experiments were performed at various pHs ranging between 2.8 – 5.3 by using acetate

buffer, to find out its effect on uptake of Pb2+

and Cu2+

ions. The optimum pH was found to be 4 for

Pb2+

and 5.3 for Cu2+

. pH has very strong effect on the adsorption capacities as can be seen in

Fig 5.9; the adsorption of Cu2+

at pH 2.8 is almost zero while it is 4.1 mmol/g at pH 5.3 (Fig 5.9)

Figure ‎5.9 pH dependence of metal uptake by CDAPE 5

This shows very beneficial property of the resin that optimum adsorption has to be done between pH

5 to 5.5 while desorption will be effective below pH 3. Hence, charging and recharging of metal ions

is pH controlled. At higher pH values, the hydrolysis of the metal ions occurs by the formation of

metal hydroxides, which compete with the metal ion uptake by the resin [254]

.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0 2 4 6 8

qP

b+

2

(m

mo

l.g-1

)

pH

Pb

Cu

138

The activation energy of the adsorption process can be calculated by plotting lnk2 versus 1/T (Table

5.1) as shown in Fig. 5.10. Using Arrhenius equation (Eq. 11), the activation energies were found to

be 3.84 and 31.86 kJ/mol for the adsorption of Cu2+

and Pb2+

, respectively. These Ea values are

relatively low in comparison to typical chemical reactions with activation energies of 65 – 250

kJ/mol, thereby indicating that the adsorption of the metal ions is relatively easy and a favored

process [294]

.

Adsorption experiments were also performed to obtain the thermodynamic parameters, and the

results are illustrated in Fig. 5.2 As can be seen from the Fig., the adsorption capacity increased by

increasing the temperature, suggesting that the adsorption process is endothermic, and the increased

swelling of the polymer permits greater diffusion of the metal ions [290]

.

)11(constant303.2

nk2 RT

El a

A plot of log (qe/Ce) versus 1/T is displayed in Fig. 5.11. The thermodynamic parameters G, H

and S were calculated using Vant-Hoff equation (Eq. 12), and are tabulated in Table 5-4 [234,235]

.

139

Figure ‎5.10 Arrhenius plot for adsorption of Cu2+ and Pb2+ on CDAPE5

Table ‎5-4 Thermodynamic Data for Pb2+ and Cu2+ adsorption

y = -3.8323x + 13.505 R² = 0.9902

y = -0.4621x + 2.1846 R² = 0.9986

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45

lnk 2

1/T X 103 ( K-1 )

Arrhenius plot

Pb

Cu

metal

ion Temp ΔG ΔH ΔS R2 Ea

KJ.mole-1

KJ.mole-1

J.K-1

mole-1

KJ.mole-1

Pb 295 -7.6512

6.043 46.420 0.999 31.859 308 -8.2546

323 -8.9509

Cu 295 -9.3019

1.428 36.374 0.995 3.841 308 -9.7748

323 -10.3204

140

Figure ‎5.11 Vant-Hoff's plot for adsorption of Cu2+ and Pb2+ on CDAPE 5

The negative G values ascertain the spontaneity of the adsorption process. As the

)12(303.2303.2

)(logR

S

RT

H

C

q

e

e

temperature increases the G values become more negative thereby indicating that the adsorption is

more favorable at higher temperatures. Favorable adsorption at higher temperatures is attributed to

the greater swelling of the resin and increased diffusion of metal ions into the resin. Greater

dissociation of zwitterionic phosphonate motifs, NH+….

P(=O)(OH)O- to zwitterionic/anionic motifs,

y = -0.0746x + 1.8997 R² = 0.9985

y = -0.3156x + 2.4244 R² = 0.9983

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45

log(

qe/

Ce)

1/T X 103 ( K-1 )

Vant-Hoff's plot

Cu

Pb

141

NH+….

P(=O)(O-)2, at elevated temperatures is also expected to increase the electrostatic attractions

between the metal ions and ion exchange groups. The positive values of H certify that the

adsorption is an endothermic process. In addition, it can be found in Table 5-4 that the S values

are positive, suggesting that the randomness increased during adsorption of metal ions as a result of

release of water molecules from the large hydration shells of the metal ions.

[ ]n

M+2

P

O

O

O

[ ]n

P

OO

OM+2

NN

Metal-complex: aminopropylphosphonate as tridentate and bidentate ligand

Scheme ‎5-2

As reported in the literature [291,292,296]

the aminomethylphosphonate motifs are potentially tridentate

ligands, having one coordination site at the nitrogen and two bonding sites at the phophonate motif,

aminomethylphosphonate have the similar structure except the spacer which is of three carbon.

Towards the weak acid range the formation of metal-complex using the aminophophonate motif as a

tridentate ligand (especially at low loads) is depicted in Scheme 5−2. At high loads, complexes

without the amino group would result using phophonate motif as a bidentate lignd.

142

5.3.6 SEM images and EDX

Scanning electron microscopy was used to examine the surface morphology of the unloaded and

loaded CDAPE 5 with Cu2+

and Pb2+

. Dried samples were sputter-coated for 6 min with a thin film

of gold and subjected to scan. In conjunction with SEM, the energy dispersive X-ray

(EDX).spectroscopy was also used to determine elemental composition of the resin before and after

the metal adsorption by randomly selecting areas on the solid surfaces. The EDX spectrum for

unloaded CDAPE 5 indicated the presence of C, N, O, Na, P, and S in the structure (Fig 5.12a);

whereas the spectra in Fig 5.12b,c revealed the presence of characteristic peaks for Cu and Pb,

respectively. Absence of Na peak in the loaded samples assures its cationic exchange with the metal

ions. A rough cracked surface of the unloaded sample (Fig 5.12a), allows greater area for

adsorption, whereas smoother and uniform surfaces of the loaded samples Fig 5.12b,c are due to the

adsorption of metal ions. The SEM images thus showed that CAPE 5 adsorbed both the metals, and

the adsorption process happened on the surface and throughout the polymer which was confirmed by

energy-dispersive X-ray spectroscopy (EDX analysis).

143

loaded CDAPE 5 with Cu2+

EDX of loaded CDAPE 5 with Cu

2

EDX of loaded CDAPE 5

with Pb2+

loaded CDAPE 5 with Pb2+

Unloaded CDAPE 5 EDX of Unloaded CDAPE 5

Figure ‎5.12 EDX and SEM images for unloaded and loaded CAPE 5 with Pb2+ and Cu2+.

a)

b)

c)

144

5.3.7 Desorption experiment

The recycling and reuse is an important criteria for the effective usage of adsorbent in industry.

Desorption experiment was conducted by stirring 100 mg of loaded resin in 2 M HNO3 for 30 min.

The amount of Cu2+

ions desorbed in the filtrate was determined after filtration, and the efficiency of

the desorption process was calculated by the ratio of desorbed amount of Cu2+

ions to the amount of

adsorbed Cu2+

ions on the resin. The percent efficiency of the desorption process is found to be

85.5% and 78.6% for Cu2+

and Pb2+

ions, respectively. It can be concluded that the novel cross-

linked polymer used in this work shows potential as an effective adsorbent for extraction and

recovery of metal ions from brackish as well as wastewater.

5.4 Conclusion

A novel cross-linked polyphophonate was prepared in excellent yield from inexpensive

starting materials. The resin was found to have an excellent adsorption capacity for Pb2+

and Cu2+

ions. The adsorption followed Langmuir, Freundlich and Temkin isotherm models as well as

Lagergren second-order kintetic model. The negative G’s and positive H’s ensured the

spontaneity and the endothermic nature of the adsorption process. The excellent adsorption and

desorption efficiencies implied the efficacy of the resin in removing as well recovering the metal

ions from aqueous solution. The effective recycling of the resin and its reuse would enable it to be

used in the treatment of contaminated water in industry.

145

6 CHAPTER 6 : ENVIRONMENTALLY BENIGN INHIBITORS

FOR GYPSUM SCALE

6.1 Introduction

Saudi Arabia has the largest water desalting capacity in the world with a share of 21 % of the

world desalting capacity (25.909x106 m

3/d) and 48 % of Gulf capacity (11.357x10

6 m

3/d) (IDA,

2000). In GCC countries, about 82 % of the desalted water is produced by Multi-Stage-Flash

(MSF) process and 12 % by Reverse Osmosis (RO) process. However, the total number of RO

plants operating in the Gulf region is much more than the MSF plants but, these units have small

production capacity and are used to desalinate brackish water for specific industrial or urban

applications. Moreover, high population growth in the country, rapid urbanization, phenomenal

industrial growth and agricultural development make water one of the most precious resources in

the Kingdom. Therefore, it is envisaged that different technologies involved in producing

desalted water are of strategic importance to the Kingdom.

The deposits commonly encountered in desalination process include mineral scales (i.e., CaCO3,

CaSO42H2O, CaSO4½H2O, CaSO4, Mg(OH)2), corrosion products, polymeric silica and

suspended matter. Davey presented an excellent review on the role of additives in precipitation

processes. Logan and Walker [255]

reported the possible mechanism for the prevention of scale

formation. Harris [256]

discussed the effect of various additives in retarding the precipitation of

alkaline scale (e.g. calcium carbonate, magnesium hydroxide) and sulfate scale in desalination

plants.

146

Poly(acrylic acid) and poly(acrylamide) are often used as water-soluble polymers with anti-scale

properties, but they do not exhibit biodegradability.[96,257]

These polymers pollute the natural

world, with grave environmental consequence. Therefore there is a demand for biodegradable

water-soluble polymer. Poly(amino acid), which has an amide linkage as well as a peptide, is

completely biodegradable [97- 99]

and as such it has attracted considerable attention as a candidate

for biodegradable, water-soluble polymer for industrial application. Sodium polyaspertte

(SPASP) a poly(amino acid) with carboxylic acid side chains, exhibit both biodegradability and

functionality such as chelating ability and dispersibility.

Among poly(amino acid) with carboxylic acid groups, poly(aspartic acid) (PASP) has been

prepared by thermal polycondensation of aspartic acid (ASP) in the presence of acid as a catalyst

as well as a solvent to form poy(succinimide) (PSI) followed by hydrolysis.[258-259]

. Matsubara;

et.al discussed a detailed characterization by NMR for the propagation & synthesis of

Polyaspartate and some of its derivatives [260]

. Sodium polyaspartate has been tested for its

calcium ion-chelating ability.[261]

Inhibition and delay of deposit formation in membrane

processes has been investigated using polyaspartic acids and their mixtures with surfactants and

emulsifiers in the presence of polyacrylates or phosphonates.[262]

. Polyaspartate and 1-

hydroxyethylidene-1,1-diphosphonic acid with wt. ratio of 1:20-1:1 has been used as a composite

scale inhibitor.[263]

. Another report discusses the effect of different factors on scale inhibition

performance of polyaspartic acid to calcium carbonate and on crystallization of calcium

carbonate.[264]

. A of composite Dendritic polymer and sodium of polyaspartic acid scale

inhibitor capable of inhibiting deposition of silica scale in water has been reported.[265]

The said

dendritic polymer is ethylenediamine core-based polyamide-amine dendritic polymer.

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147

Compound scale inhibitor containing polymer and organic phosphonic acid have been applied

for water treatment.[266]

The polymer based scale inhibitor is selected from ≥1 of polyacrylic

acid, acrylic acid derived polymer, acrylic acid and acrylic acid derivatives copolymer,

polymaleic acid, maleic acid derived polymer, maleic acid and maleic acid derivatives

copolymer, polyepoxy succinic acid, polyvinylpyrrolidone, vinyl pyrrolidone derived polymer,

sulfonated styrene derivatives polymer, polyaspartic acid, aspartic acid derivatives polymer.

The optimal preparation of scale inhibitor polyaspartic acid has been reported recently.[267]

A

Study on the function mechanism of phosphonic acid modified polyaspartic acid scale inhibitor

has been reported.[268]

In reverse osmosis systems with high silica water severe and irreversible membrane scaling can

be observed. A study [269]

report the results of laboratory experiments about the influence of Ca2+

and Mg2+

ions on the behavior of supersaturated solutions of silica in different test waters. The

applied different methods of analysis enabled the differentiation of three groups of silicates:

‘monomeric’, ‘polymeric’ and ‘filterable’. It has been shown, that the ‘polymeric silica’ is

mainly responsible for the membrane scaling. The kinetic of the formation of ‘polymeric silica’

is strongly influenced by the cations and the pH-value. Between pH 6.5 and 8.5 the

polymerization is relatively fast but it decreases to very low values at pH 5.5. Antiscalant

Osmotech 1309, based on phophonic acids, phophonocarboxylic acid and special polycarboxylic

acids, are efficient scale inhibitors against various minerals and designed specifically against

various minerals and designed especially against silica fouling. It has been demonstrated that the

use of a suitable antiscalant makes it possible to operate the plant at significantly higher recovery

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148

rates. At pH 7 the silica particles are negatively charged and repel each other. In the presence of

added salt, the charge repulsion is screened and aggregation and gel formation occur.

Silica inhibitors retard polymerization of monomeric silica. Examples of polymeric silica

dispersants are based on phophonate, carboxylate and sulfonates.[270]

Many of the developed

products are proprietary. Silica in water is in the reactive or unreactive form. The reactive form

refers to monomeric SiO4. The polymerized form results when the silica concentration exceeds

the saturation limit at the use conditions. Unreactive silica consists of polymerized silica as well

as colloidal and granular silica. Silica solubility limits water use in applications such as reverse

osmosis (RO). Silica concentrations above 150 to 180 mg/L at ambient temperatures will cause

accelerated fouling owing to polymerization to form colloidal silica which will foul membranes.

A scale inhibitor composed of main components and auxiliary agents have been used [271]

The

main components comprise hydroxyethylidene diphosphonic acid, sodium polyacrylate,

hydrolyzed poly(maleic anhydride), and poly(epoxysuccinic acid). The auxiliary agents

comprise sodium bisulfite, chlorine dioxide, and benzotriazole. The product has high scale

inhibition ratio (85%) for calcium carbonate, calcium sulfate, barium sulfate, calcium fluoride,

and silica scale in water. The product has been claimed to have synergistic effect, stable

performance, and low cost.

Sodium hexametaphosphate has been used as a silica-scale inhibitor to prevent or remove or

reduce scale deposits from concentrated water.[272]

149

In accordance with the principles of responsible care, a general product profile for ecologically

benign inhibitor systems has been proposed as follows: (1) excellent scale inhibition; (2) low

aquatic and human toxicity; (3) high biodegradability; (4) low water hazard class (maximum of

2); (5) good price/performance ratio; and (6) free of phosphorus, nitrogen, and heavy metals.[273]

.

Keeping these entire challenging requirements in mind, there is a need to develop antiscalants

that readily biodegrade and have low mobility for minimum environmental impact and perform

at cost-effective dose rates.

poly(aspartic) based inhibitors are currently, the most promising alternative to conventional

nondegradable inhibitors. In the present research we synthesize various polysuccinimide PSI and

sodium aspartate homo and copolymers with cyclic and aliphatic amine pendants in different

ratios. The anstiscaling properties of these inhibitors are found to be very promising even at very

low concentration as 2.5 ppm while treating it with 3 times the concentration of calcium and

sulfate found in concentrated brine (CB).

6.2 Experimental

6.2.1 Materials

L-Aspartic Acid (ASP) was purchased from (Fluka Chemie AG ), .1,3 dibromopropane AnalR,

BDH) potassium pthalimide, hydrazine hydrate, (Fluka Chemie AG) sulfolane N,N-

dimethylformamide (Fluka Chemie AG) o−phosphoric acid (85% certified ACS Fischer

Scientific), sulfuric acid (98% certified ACS Fischer Scientific), sodium hydroxide (Fluka

Chemie AG), pyrrolidine, piperidine and azepane (Fluka Chemie AG ) were used as received..

150

6.2.2 Physical methods

Melting points were recorded in a calibrated Electrothermal-IA9100- Digital Melting Point

Apparatus. Elemental analysis was carried out on a Perkin Elmer Elemental Analyzer Series 11

Model 2400. IR spectra were recorded on a Perkin Elmer 16F PC FTIR spectrometer. 1H,

13C

and 31

P NMR spectra were measured in CDCl3 (using TMS as internal standard) or D2O at +25

°C (using HOD peak at 4.65 and the 13

C peak of dioxane at 67.4 ppm as internal standard) on

a JEOL LA 500 MHz spectrometer. 31

P spectra were referenced with 85% H3PO4 in DMSO.

151

6.2.3 Synthesis of monomers

Diethyl (3- bromopropyl) phosphonate 2 was synthesized as described in literature [121,274]

while

diethyl 3-azidopropylphosphonate 3 is prepared as described in reference [275]

. The NMR spectra

of 2 and 3 match with those reported in the literature (Scheme 6-1). Repeated hydrogenation of

compound 3 by using procedure as described in the literature [319]

afforded unexpectedly a

mixture of diethyl 3-aminopropylphosphonate 4 and its dimer 5 in variable quantities under

different hydrogenating conditions. Note that the article reported the formation of

monophosphonate 4 alone; our hydrogenation procedure confirmed that the compound reported

is in fact 5 instead of their claim to be monophosphonate 4.

Compound 3 (12.4 g; 56 mmoles) in ethanol (85 mL) was hydrogenated at room temperature

using 1.5 g Pd/C at 3 atmospheres for 24 h. After filtration and removal of solvent the residual

liquid revealed the presence of 4 and 5 in a ratio of 1:1.2 . Silica gel TLC with ethyl

acetate/methanol/methanol (NH3) (4:1:1) revealed the presence of 4 and 5 with Rf value of 0.14

and 0.4 respectively. The compounds were separated by silica gel chromatography using

ether/methanol mixture as eluent which gave 5 (5.6 g) a light yellow liquid. Continued elution

gave 4 (4.3 g) also as a light yellow liquid.

Monomer 4 H (500 MHz,CDCl3), 1.33 (6H, t, J 7.0 Hz); 1.59 (2H, bs); 1.76 (4H m);

2.77 (2H, t, J 6.6 Hz) 4.10 (4H, m); C (125 MHz,CDCl3), 16.48 (2C, d, J 6.2 Hz); 23.04 (1C, d,

J 142.4 Hz); 26.48 (1C, s,); 42.51 (1C, d, J 16.5 Hz); 61.46 (2C, d, J 6.2 Hz) P (202.35

MHz,CDCl3), 32.46 (1P, t, J 9.8 Hz).

152

Dimer 5 H (500 MHz,CDCl3), 132 (12H, t. J 7.0 Hz); 1.77 (9H, m); 2.67 (4H, t, J 6.6 Hz);

410 (8H, m); C (125 MHz,CDCl3), 16.15 (4C, t, J 8.3 Hz); 22.60 (2C, d, J 12.4 Hz); 23.66 (2C,

d, J 6.2 Hz); 49.43 (2C, d, J 24.8 Hz); 61.19 (4C, d, J 6.2 Hz);

Dimer 5 (2.3 g, 11.8 mmol) was heated with 1:1 HCl (10.0 mL) at 100oC for 24 h. After removal

of solvent the residual liquid was analyzed by NMR: H (500 MHz, D2O), 1.60-1.77 (4H, m);

2.94 (2H, t, J 7.7 Hz) C (125 MHz, D2O), 20.31 (2C, s); 24.39 (2C, d, J 138.2 Hz); 48.46 (2C, d,

J 18.6 Hz), dioxane (67.40ppm) P (202.35 MHz, D2O), 28.79 (1P,t, J 12.2 Hz).

Monomer 4 was also hydrolyzed by the same procedure as above to get 6, and analyzed by NMR

H (500 MHz,D2O), 1.55-1.75 (4H, m); 2.86 (2H, m) C (125 MHz,CDCl3), 21.29 (1C, s); 24.20

(1C, d, J 136 Hz); 40.53 (1C, d, J 18.6 Hz) dioxane (67.40 ppm) P (202.35 MHz, D2O), 28.16

153

NH2

P O

O -

- O

7

Br

Br

P(OEt)3

Br

P OEtO

OEt

NaN3

N3

P OEtO

OEt

H2/Pd-C

NH2

P OEtO

OEt

HCl/H2O

NH3+Cl -

P OHO

OH

NaOH

1 2 3

4 6

NH2

P OEtO

OEt

4 5

+

P(OEt)2O

(EtO)2PO

NH

Scheme ‎6-1

154

Scheme ‎6-2

OH

OH

O

O

H2N H2SO4

N

O

O

[]

n

Scheme 2.

Aspartic acid 8

H3PO4

Sulfolane

H3PO4 30% wt/wt; 3h

180oC; 25mm Hg

1mm Hg, 1 h

Aspartic acid 8 Polysuccinimide 9 (molar mass 19000; DP 190)

Aspartic acid 8Polysuccinimide 9 (molar mass 100000; DP 1000)

200oC

105oC

~~

~~ ~~

~~

Polysuccinimide 9 (molar mass 7000; DP 70) ~~ ~~

155

Scheme ‎6-3

N

O

O

[]

n

Scheme 3.

n]

NaOH

0.77 equiv

NH

O

ONa+ -O

[

Sodium polyaspartate 10

NaOH

0.77n0.23n

Na O

NH

O

O

N

O

O

[]

[]

Sodium polyaspartate-ran-polysuccinimide 11

~~ (DP 70)

~~ (DP 70)

~~

Polysuccinimide 9 (molar mas 7000;DP 70) ~~

156

Scheme ‎6-4

[]

n

N

NH

O

O

[]

n

N

NH

O

O

N

O

O

[]

n

Scheme 4.

Polysuccinimide 9 (molar mass 7000; DP 70)

1 equiv

NH

NH

1 equiv

Poly(azepan-1-yl)aspartamide 13

Poly(pyrrolidin-1-yl)a spartamide 12 ~~ ~~~~(DP 70)

~~(DP 70)

157

Scheme ‎6-5

NH

Scheme 5.

0.5n0.5n

NH

0.5 equiv

NaOH

0.5 equiv

NaOH

0.5 equiv

N

O

O

[]

N

NH

O

O

[]0.5n

0.5n

[

N

NH

O

O

NH

O

ONa+ -O

[]

]

0.5 equiv

H2N(CH2)3P(OEt)2

O

0.5 equiv H

N

O

O

[] [

]0.5n0.5n

(CH2)3

P(OEt)2O

N

NH

O

O

]

[

0.5n

[N

O

O

]

N

NH

O

O

0.5n

Poly[(piperidin-1-yl)aspartamide-ran-

sodium aspartate] 17

~~(DP 70)

Poly[(piperidin-1-yl)aspartamide-ran-

polysuccinimide] 16 ~~(DP 70)

Poly[(pyrrolidin-1-yl)aspartamide-ran-

sodium aspartate] 15 ~~(DP 70)Poly[(pyrrolidin-1-yl)aspartamide-ran-

polysuccinimide] 14 ~~(DP 70)

~~(DP 70)

Poly[(3-diethoxyphosphonylprop-1-yl)a spartamide

-ran-polysuccinimide] 18

N

O

O

[]

n

Polysuccinimide 9 (molar mass:7000; DP 70) ~~

0.5n0.5n

N

NH

O

O

NH

O

ONa+ -O

[]

[]

158

Scheme ‎6-6

Scheme 6.

NH

0.5 equiv

0.5nN

O

O

[]

N

NH

O

O

[]0.5n

Poly[(azepan-1-yl)a spartamide-ran-

polysuccinimide] 19 Poly[(azepan-1-yl)a spartamide-ran-


NaOH

0.5 equiv

~~(DP 70) ~~(DP 70)

N

O

O

[]

n

~~

Polysuccinimide 9 (molar mass:7000; DP 70)

0.5n0.5n

N

NH

O

O

NH

O

ONa+ -O

[]

[]

159

Scheme ‎6-7

N

O

O

[]

n

0.5 equiv

N

O

O

[]

N

NH

O

O

Azepane

0.5 equiv NaOH

[]N

H

O

ONa+ -O

n

Scheme 7

N

NH

O

O

NH

O

ONa+ -O

[]

[]

~~ ~~


0.5n

0.5n0.5n

0.5n ][


polysuccinimide] 19

~~(DP 190)

~~(DP 190)



Sodium polyaspartate 10

~~(DP 190)

1 equiv NaOH

N

O

O

[]

n

0.5 equiv N

O

O

[]

N

NH

O

OAzepane


~~ ~~

0.5n

[]0.5n

~~


sodium aspartate] 20 ; (DP 1000)

160

6.2.4 General procedure for polymer Synthesis

6.2.4.1 PSI with Mw 7000

A mixture of H2SO4 (2.5 g) and L -Aspartic acid (50 g, 376 mmol) (entry 3, Table 1) was

thoroughly grinded in a porcelain mortar at room temperature. The mixture was then transferred

to a two-necked round bottomed flak fitted with a large air condenser and heated in an oil bath at

203 ºC under Nitrogen atmosphere. Water vapor, deposited in the condenser, was swept off by

N2 purge. The mixture was stirred continuously using a magnetic stir-bar. Clumps, formed after

30 min, were finely grinded again in mortar and heated for further 7 h. A pale white powdered

product (polysuccinimide 8 DP≈70 Scheme 2) was washed with several portions (300 mL) of hot

water to remove unreacted aspartic acid as well as H2SO4. Final wash has been done by methanol

(150 mL) and the product was dried under vacuum at 85oC for 2 h (till constant weight).

6.2.4.2 PSI with Mw 19000

A suspension of ASP (37.7 g, 388 mmol) (entry 1 Table 1) and 85% Phosphoric acid (1.62 g,

14.1 mmol) in sulfolane (120 g) was refluxed under N2 at 160 ºC in an oil bath for 5 h. The

reaction mixture containing the insoluble white product (polysuccinimide 8 DP ≈190 Scheme 2)

was filtered off and washed with methanol (100 mL) then several times with water until the

washing becomes neutral, and finally with methanol (100 mL). The residue was crushed and

dried under vacuum at 900C for 2 h (till constant weight).

161

6.2.4.3 PSI with Mw 100,000

L-Aspartic acid was mixed with 30 wt% phosphoric acid, and the mixture was heated at 180°C

for 3 h under reduced pressure (25 mm Hg) and then for 1 h under higher vacuum at 1 mm Hg.

The mixture was cooled to room temperature and dissolved in DMF (100 mL). The solution was

then poured into a large excess of water. The precipitated polymer (polysuccinimide 8 DP~1000

Scheme 2) was filtered, washed with water and methanol and then dried to a constant weight

under vacuum at 85°C. The procedure is expected to give PSI with an Mw of 100,000.

6.2.4.4 PSI derivatives

PSI (2.0 g, 20 mmol) (Table 2) was dissolve in DMF (10 mL) while stirring with a magnetic stir-

bar in a round bottomed flask. The solution was cooled to 0oC in an ice bath and amine

(pyrrolidine or piperadine or azepane or diethyl(3-aminopropyl)phosphonate, 10 mmol) was

added drop wise for 5 min. The mixture was stirred at room temperature for 7 h. After the

completion of reaction, the mixture was poured dropwise into vigorously stirr acetone (20 mL).

Pale white product of poly[(prrolidine-1-yl)aspartamide 12 (DP≈70); poly[(azepane-1-

yl)aspartamide] 13 (DP≈70) (Scheme 4); poly[(prrolidine-1-yl)aspartamide-ran-

polysuccinimide] 14 (DP≈70); poly[(piperidine-1-yl)aspartamide-ran-polysuccinimide] 16

(DP≈70); poly[(3-ethoxyphosphonylprop-1-yl)aspartamide-polysuccinimide] 18 (DP≈70)

(Scheme 5); poly[(azepane-1-yl)aspatamide-ran-polysuccinimide] 19 (DP≈70, 190 and 1000)

(Scheme 6 and 7) precipitated out. The clear supernatant solvent was decanted and the product

soaked overnight in a portion of fresh acetone. The product was filtered and washed with acetone

162

and dried under vacuum at 70oC for 1 h. Lumps formed were crushed, ground and dried again

under vacuum for further 1 h (till constant weight).

6.2.4.5 Alkaline hydrolysis of PSI/ PSI derivatives

PSI/ PSI derivative (10 g, 103 mmol) (Table 3) was added gradually while stirring with a

magnetic stir-bar to an ice cooled solution of NaOH (4.123 g, 103 mmol) in water (30 mL) for

5-8 min. Care must be taken to avoid lumping and solution is continued to be stirred at room

temperature for 3 h. After the completion of reaction, the mixture was poured dropwise onto a

vigorously stirring acetone (200 mL), extremely hygroscopic white sticky product of Sodium

Polyaspartate 10 (DP≈70), Sodium Polyaspartate-ran-polysuccinimide 11 (DP≈70) (Scheme 3);

poly[(prrolidine-1-yl)aspartamide-ran-sodium aspartate] 15 (DP≈70); poly[(piperidine-1-

yl)aspartamide-ran-sodium aspartate] 17 (DP≈70); (Scheme 5); poly[(azepane-1-yl)aspartamide-

ran-sodiumaspartate] 20 (DP≈70 and DP≈190) (Scheme 6 and 7)} precipitated out. The clear

supernatant solvent was decanted and soaked overnight in acetone. The product was filtered and

washed with acetone and dried under vacuum at 70oC for 1h. Lumps formed were crushed,

ground and dried under vacuum for 1 h (till constant weight).

163

Table ‎6-1 Polycondensation of Aspartic Acid

Exp # Solvent Acid Catalyst Reaction Reaction *Productive Mw

Temp Time Yield

OC h %

9 (DP ≈ 190) sulfolane H3PO4 160 6 63 19000

9 (DP ≈ 70) - H2SO4 203 7 48 7000

* Low yield is due to the suction of light weight powdered product during vacuum drying

Table ‎6-2 Synthesis of PSI derivatives

EXP # PSI Type of Molar Ratio DMF Reaction Reaction Yield

Mw Amine PSI : Amine Temperature Time

mL oC h %

14 (DP ≈ 70) 7000 Pyrrolidine 2:1 10 RT 17 95 14a (DP ≈ 70) 7000 Pyrrolidine 2:1 40 RT 12 92 16 (DP ≈ 70) 7000 piperidine 2:1 50 RT 15 88 19 (DP ≈ 70) 7000 Azepane 2:1 37 RT 15 84 13 (DP ≈ 70) 7000 Azepane 1:1 30 RT 15 74

18 (DP ≈ 70) 7000 Diethyl(3-aminopropyl)

phosphonate 2:1 10 RT 22 74 12 (DP ≈ 70) 7000 Pyrrolidine 1:1 40 RT 26 70

19 (DP ≈ 1000) 100,000 Azepane 2:1 37 RT 22 77 19 (DP ≈ 190) 19000 Azepane 2:1 37 RT 22 80

RT = Room Temperature

Table ‎6-3 Alkali hydrolysis of PSI and PSI derivatives

EXP # PSI Type of Molar Ratio Reaction Reaction Yield

Mw Amine polymer: NaOH Temperature Time

oC h %

10 (DP ≈ 190) 19000 - 1:1 RT 4 85 10 (DP ≈ 70) 7000 - 1:1 RT 3 98

11 (DP ≈ 70) 7000 - 1.3:1 RT 3 98 17 (DP ≈ 70) 7000 piperidine 2:1 1:1 RT 2 73 20 (DP ≈ 70) 7000 Azepane 2:1 1:1 RT 2 96 15 (DP ≈ 70) 7000 Pyrrolidine 2:1 2:1 RT 1 89

20 (DP ≈ 190) 19000 Azepane 2:1 2:1 RT 1 *58 RT = Room Temperature * Low yield is due to the extremely hygroscopic nature of the product, lost during

workup.

164


The brine concentrations and temperatures encountered in Reverse Osmosis (RO) desalination

process were considered to study the precipitation and inhibition of calcium sulfate (gypsum)

using a series of the newly synthesized environmentally benign antiscalants.

A typical analysis of brackish water and reject brine from RO plant at King Fahd University of

Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia is given in Table 4. The concentration

of reject brine (i.e., concentrated brine) at 70 % recovery and 98% salt rejection (Table 4) was

denoted as CB. A mathematical model is applied on the basis of analyzed feed water to find out

the concentrations of ions in Concentrated Brine. Analysis of brine in RO Plant at King Fahd

University of Petroleum & Minerals (KFUPM) revealed the concentration of Ca2+

in the

brackish feed water and in the reject brine as 281.2 and 943.3 ppm respectively; while the

corresponding concentration of SO42-

are 611 and 2,100 ppm [45]

. The evaluation of the newly

synthesized series of scale inhibitor was performed in solution containing Ca2+

and SO42-

3 times

of the concentrated brine (CB). It has been confirmed from solubility data of CaSO4 that 3 CB

solutions would be supersaturated with respect to CaSO4.

165

Table ‎6-4 Analysis of feed water and reject brine showing major species in RO Plant at KFUPM, Dhahran

Item Brackish Watera

Cations Feed

(mg/l)

Reject Brine at

70 % recovery;

98% salt rejection

(mg/l)

Al3+

< 1.0 < 1.0

Ba2+

< 0.05 0.2

Ca2+

281.2 943.3

Cu2+

< 0.05 0.2

Fe2+

< 0.1 0.7

K+ 32.0 88.9

Mg2+

88.9 300.7

Mn2+

< 0.05 < 0.05

Na+ 617.2 1,653

P3+

< 0.1 0.88

Sr2+

3.98 24.3

Zn2+

< 0.05 0.07

Anions

Br- 5.9 15.8

Cl- 1,410 3,977

F- < 0.4 < 0.4

HCO3- 241 792.1

NO3- 7.7 24.3

PO43-

< 0.6 < 0.6

SO42-

611 2,100

Others

SiO2 29.8 89.4

TDS 3,329 10,321

I (moles/l) 0.06995 0.2087

pH 6.8 7.2

aSource: Dhahran brackish water, Butt et al., 1995(Ref.45).

166


and SO42-

ions equals to 6 times the concentrated brine (CB) were

prepared by dissolving the calculated amount of CaCl2 and Na2SO4, respectively, in deionized

water. The solutions were filtered through membrane filters (0.45 μm, Millipore) and

standardized by EDTA complexometric titration (Metrohm autotitrator) and ion chromatography

(Dionex ICS-3000) for calcium and sulfate respectively.

A solution of 6 CB calcium chloride (60 mL) containing antiscalant (20 ppm) was taken in a

round bottom flask and heated at 40ºC 1ºC. A preheated (40 ºC) solution of 6 CB sodium

sulfate (60 mL) was added quickly to the flask, the content of which was stirred at 300 rpm

using a magnetic stir-bar. The resultant solution containing 10 ppm of antiscalant thus becomes

3 CB which is 3×943.3 mg/L i.e. 2830 mg/L in Ca2+

and 3×2100 mg/L i.e. 6300 mg/L in SO42-

.

The progress and the extent of the crystal growth process both in the presence and in the absence

of the inhibitors tested, was characterized by the decrease of the solution conductivity as a

function of time. Conductivity measurements were made at an interval of every 10 s initially and

then with a period of 10 min, to quantify the effectiveness of newly developed series of

antiscalants. The drop in conductivity indicates the precipitation of CaSO4. Induction time was

measured with a decrease in conductivity when precipitation started. The experiments were

continued till equilibrium is reached. Visual inspections were carefully done to see any turbidity

arising from precipitation.

167


6.3.1 Scale inhibition properties of the synthesized polymers

In Reverse Osmosis (RO) process, outcome of the feed water are product water and reject brine.

The dissolved salts in the feed water are concentrated in the reject brine stream. If

supersaturation occurs and their concentration exceeded the solubility limits, precipitation or

scaling will occur. The percent scale inhibition is calculated using the following Equation:

100][][

][][%

)(

2

)(

2

)(

2

)(

2

0

tblanktinhibited

tblanktinhibited

CaCa

CaCaInhibitionScale

where )(tinhibited

2

0][Ca

is the initial concentration at time zero, [Ca2+

] inhibited (t) and [Ca2+

]blank (t)

are the concentrations in the inhibited and blank solution (without antiscalant) at time t.

For the current work, the precipitation behavior of a supersaturated solution of CaSO4 containing

2600 ppm of Ca2+

and 6300 ppm of SO42-

in the absence and presence of antiscalants was

investigated. Conductivity measurements were made at an interval of every 10 s in case of

control sample (Blank; without antiscalants) while the interval was 10 min in case of inhibited

samples, to quantify the effectiveness of newly synthesized antiscalants. Induction Period was

measured when precipitation started which was observed by a drop in conductivity.

Induction Period and % inhibition of newly synthesized antiscalants at different dose

concentration are shown in Table 6−1 It is obvious that the hydrolyzed species 15, 17 and 20

168

have more antiscaling effect than unhydrolyzed 13,14,16,18 and 19, also higher molecular

weight polymers 19 (DP≈190 and DP≈1000) were found to be less effective than low molecular

weight polymers 19 (DP≈70). The ring size of the pedant amine also related inversely to the

CaSO4 scale inhibition i.e. (14 < 16 < 19). One more interesting feature revealed from Table 1 is

that the induction period decreases as we increase the ratio of pendant group from 2:1 to 1:1 (14

> 12 and 19 > 13). Moreover, results also indicate that the duration of the induction period is

greatly influence by changing the concentration of the antiscalants. As shown in Figure 5, the

crystallization reaction in the presence of copolymer (10 ppm) is preceded by an induction period

of several minutes to several hours after which the growth recommences with a measurable rate.

Note that in the absence of antiscalant, the spontaneous precipitation started immediately, as

indicated by the drop in conductivity (Fig. 1: Blank).

Figure ‎6.1 Precipitation behavior of CaSO4_3CB_40oC in the absence of antiscalant (blank)

15.0

15.5

16.0

16.5

17.0

17.5

18.0

18.5

19.0

19.5

20.0

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00

Co

nd

uct

ivit

y m

S/cm

Time min

Ca SO4_blank 3CB

169

Table ‎6-5 A trends of Induction period and inhibition Percentage of the synthesized polymers for CaSO4

Experimet #

Antiscalant Antiscalant Molecular

weight Concentration

Induction Period

inhibition

Name Code Mw mg/L min %

CaSO4-3CB

final Blank 0

1 10 (DP ≈ 190) SPASP 19000 10 600 12

2 10 (DP ≈ 70)

SPASP 7000

10 > 1200 91

3 10 (DP ≈ 70) 8 1100 11

4 10 (DP ≈ 70) 2.5 250

5 11 (DP ≈ 70) SPASP 1.3:1 7000

10 1000 14

6 11 (DP ≈ 70) 5 180

7 14 (DP ≈ 70) PrPSI 2:1 7000 10 25 17

8 16 (DP ≈ 70) PpPSI 2:1 7000 10 100 13

9 19 (DP ≈ 70) AzPSI 2:1 7000 10 >800 83

10 13 (DP ≈ 70) AzPSI 1:1 7000 10 600 3

11 18 (DP ≈ 70) PEPSI 2:1 7000 10 0 2

13 12 (DP ≈ 70) PrPSI 1:1 7000 10 0 2

14 17 (DP ≈ 70) PpSPASP 2:1

7000 10 >1200 97

15 17 (DP ≈ 70) 5 200 5

16 20 (DP ≈ 70) AzSPASP 2:1

7000

10 3000 6

17 20 (DP ≈ 70) 5 600

18 20 (DP ≈ 70) 2.5 130

19 19 (DP ≈1000) AzPSI 2:1 100,000 10 50 5

20 19 (DP ≈ 190) AzPSI 2:1 19000 10 30 0.01

21 15 (DP ≈ 70)

PrSPASP 2:1 7000

10 1800 15

22 15 (DP ≈ 70) 5 170

23 15 (DP ≈ 70) 2.5 130

24 20 (DP ≈ 190) AzSPASP 2:1 19000 10 140 15

25 Commercial Antiscalant

currently use in KFUPM RO

Plant 10 25 4

170

6.3.1.1 Effect of PSI- derivative on Induction Period of CaSO4 Scale

The effect of PSI derivatives (M w ~7000) on the crystallization of CaS04.2H20 form

supersaturated solution was studied by a series of experiments summarized in Table 1. Fig 2

shows that the crystallization reaction in the presence of PSI derivatives (10 ppm) is preceded by

an induction period of several minutes several hundred minutes after which the growth

recommences with a measurable rate. PSI-azepane has much longer induction period more than

800 min than piperidine and pyrrolidine derivatives which have 10 and 25 min of induction

period respectively.

Figure ‎6.2 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm) antiscalant showing Pendent Effect

on Scale Inhibition

15

15.5

16

16.5

17

17.5

18

18.5

19

19.5

20

-25 175 375 575 775

Co

nd

uct

ivit

y m

S/cm

Time min

PSI-derivatives Effect on Induction period

19 (DP~70)

16 (DP~70)

14 (DP~70)

18 (DP~70)

Commercial

Antiscalant

Blank 3CB

171

Commercially available antiscalants formulation also have induction period of only 25 minutes

while in case of PSI-propyl phosphonate diester immediate precipitation occur as the control

sample (without antiscalants).

6.3.1.2 ‎ ‎ w of Sodium Polyaspartate on CaSO4 scale inhibition

The inhibiting behavior of the additives also depends on the weight average molecular weight of

the polyaspartate back bone shown in Fig 3. It reveals that higher Mw (≈19000) Polyaspartate 10

(DP≈190) has induction period of only 600 min while 10 (DP≈70) low Mw (≈7000) has more

than 1200 min.

Figure ‎6.3 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm) antiscalant showing effect of SPSI

Mw

15

16

17

18

19

20

0 200 400 600 800 1000 1200 1400

Co

nd

uct

ivit

y m

S/c

m

Time min

Effect of SPASP Mw

10 (DP~70)

10 (DP~190)

Blank

172

6.3.1.3 Effect of Mw of PSI- derivative on CaSO4 scale inhibition

As far as the weight average molecular weight is concern PSI-derivatives also have the similar

trend as that of corresponding sodium polyaspartate with the exception that 19 (DP≈1000) (M w

~100,000) has little more induction period (50 min) than 19 (DP≈190) (Mw ≈19000) has 30 min,

while the one with lowest Mw ≈7000 has more than 900 min.

Figure ‎6.4 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm) antiscalant showing effect of M w of

PSI- derivative on CaSO4 scale inhibition

15

16

17

18

19

20

0 200 400 600 800 1000

Co

nd

uct

ivit

y m

S/c

m

Time min

Effect of Mw on CaSO4 scales

19 (DP~70)

19 (DP~190)

19 (DP~1000)

Blank

173

6.3.1.4 Effect of Sodium Polyaspartate derivatives on CaSO4 inhibition

It is quite obvious from Figure 5 that the pendant cyclic amine group increases the scale

inhibition efficiency of polyaspartate to a great extent. 20 (DP≈70) azepane sodium aspartate, 7-

membered cyclic amine derivative, has the largest induction period of >3000 min among all of

the synthesized polymers in Table1. The induction period is then gradually decreases with

decrease in the ring size of the pendant group i.e. 15 (DP≈70) PrSPASP, 5-membered (1800 min)

and 17 (DP≈70) PpSPASP, 6-membered is in between these two. On the other hand partially

hydrolyzed 11 (DP~70) sodium polyaspartae without any pendant has induction period of only

900 min (Figure 5), while completely hydrolyzed 10 (DP~70) has induction period of >1200

min.

Figure ‎6.5 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm) antiscalant showing effect of Sodium Polyaspartate derivatives on CaSO4 inhibition

15

16

17

18

19

20

0 1000 2000 3000 4000

Co

nd

uct

ivit

y m

S/c

m

Time min

Effect of Pendent on CaSO4 scales

20 (DP~70)

17 (DP~70)

15 (DP~70)

11 (DP~70)

Blank

174

6.3.1.5 Effect of pendant ratio

The inhibiting behavior of the additives also depends on the pendant ratio as shown in

Figure 6.6, 13 (DP≈70) having 1:1 ratio of PSI:Azepane has shorter induction period while the

copolymer 19 (DP≈70) having lower ratio i.e. 2:1 has longer. Similarly 14 (DP≈70) has

pyrrolidine:PSI of 2:1 showing induction of 25 min while 12 (DP≈70) (PSI:Pyrolidine; 1:1)

precipitated as same as control sample, with no induction period.

Figure ‎6.6 Precipitation behavior of CaSO4_3CB_40oC in the presence (10 ppm) antiscalant showing effect of

Pendant Ratio

15

16

17

18

19

20

0 200 400 600 800 1000

Co

nd

uct

ivit

y m

S/cm

Time min

Effect of Pendant Ratio 19 (DP~70)

13 (DP~70)

14 (DP~70)

12 (DP~70)

Blank

175

6.3.1.6 Effect of antiscalant dose concentration

It is apparent from Figure 6.7 that the induction period increases with the increase in dose

concentration of antiscalants though it is not linear.

Figure ‎6.7 Precipitation behavior of CaSO4_3CB_40oC at 2.5 ppm, 5 ppm and 10 ppm antiscalant concentration

a) 10 (DP≈70); b) 15 (DP≈70); c) 20 (DP≈70) and d) Commercial Antiscalant

As shown in many graphs, the crystallization reaction in the presence of copolymer is preceded

by an induction period of several minutes to several thousand minutes, later the growth

recommences with a measurable rate observe by sharp drop in conductivity.

15

16

17

18

19

20

0 1000 2000 3000 4000

Co

nd

uct

ivit

y m

S/c

m

Time min

Concentrtation effect of 20 (DP~70) 10ppm

5.0ppm

2.5ppm

Blank

15

16

17

18

19

20

0 250 500 750 1000 1250 1500 1750 2000C

on

du

ctiv

ity

mS

/cm

Time min

Concentrtation effect of 15 (DP~70) 10ppm

5.0ppm

2.5ppm

Blank

15

16

17

18

19

20

0 200 400 600 800 1000 1200

Co

nd

uct

ivit

y m

S/c

m

Time min

Concentration Effect of 10 (DP~70)

on CaSO4 scales

10ppm

8.0ppm

2.5ppm

Blank

15

16

17

18

19

20

0 50 100

Co

nd

uct

ivit

y m

S/c

m

Time min

Commercial antiscalant (RO KFUPM)

10ppm

5ppm

Blank

aa b

a

ca d

a

176

The equilibrium inhibition percentage in almost all of the above experiments are very low

(Table1), this clearly indicates that the large rate constant following the induction period, reflect

the increased number of growth sites formed during the nucleation process.

In addition, the duration of the induction periods is greatly influenced by changing the

concentrations of antiscalants. The striking effect of the polyaspartates on the induction periods

with subsequent growth of CaSO42H2O observed in the present study may be explained by an

incorporation of polyaspartates into the growing crystals. During the induction period, most of

the active growing sites may be poisoned by adsorbed polyaspartates molecules, However, some

of the growth sites of lower energy may still be free to grow, and the reaction proceeds at a very

slow rate. The changes in solution conductivity (concentration) during this stage may be too

small to be detected. After these slowly advancing steps cover the poisoned sites, the adsorbed

molecules are incorporated into growing crystal and the crystal growth can resume at a rate

comparable to that of unpoisoned systems. The results presented in this study clearly show that

in the desalination of KFUPM brackish water, the role of polyaspartates is to prolong the

induction period and thus minimize the fouling of membranes by CaSO42H2O. In the RO

application of these polyaspartates as antiscalants, the presence of induction period, followed by

a growth rate comparable to that in the absence of polyaspartates, may be perfectly acceptable

provided that the induction period is longer than the period required for membrane protection

from fouling.

177

6.3.2 EDX and SEM images

Scanning electron microscopy (SEM) analysis shown in Fig 6.8, a monoclinic CaSO4 crystal is

formed in blank solution, featuring a regular shape and compact structure. Crystals formed in

the solutions with antiscalants have irregular shapes and loose structures. Fig. 6.9 shows that in

the presence of Sodium Polyaspartate 10 (DP ≈ 70), a CaSO4 crystal loses its sharp edges, and its

morphology is modified from elongated stick forms to thin flakes. In the presence of

poly[(azepane-1-yl)aspartamide-ran-sodiumaspartate] 20 (DP ≈ 70) and poly[(prrolidine-1-

yl)aspartamide-ran-sodiumaspartate] 15 (DP ≈ 70) the crystal morphology also changes to

smaller fragments (Figs 6.10 and 6.11). The modification of crystal exhibits a cotton wool-like

shape in case of CaCO3 (Fig 6.12). Since various types of crystal faces have different surfaces,

inhibitor molecules are adsorbed at different rate onto each type of face lattice structure.

Consequently alterations in crystal shape occur during outgrowth that is, the crystal cannot grow

normally in accordance with an array of crystal lattices strictly, causing the crystals to become

distorted or increasing the internal stress of crystals. Increase in stress could result in crystal

fractures and prevention of deposition of microcrystallites [276]

.

178

Figure ‎6.8 EDX and SEM images of gypsum formed from 3CB CaSO4 after 30 seconds at 40 oC while no antiscalant

added.( Blank)

Ca

Ca

Ca

S

O

Ca

S

0 1 2 3 4 5 6 7 8 9 10

keVFull Scale 1104 cts Cursor: 3.228 (12 cts)

Spectrum 1

179

Figure ‎6.9 EDX and SEM images of gypsum formed from 3CB CaSO4 after 1200 minutes at 40 oC while using 10

ppm of Sodium Polyaspartate 10 (DP ≈‎70) as antiscalant

CuCu Cu

CuCa

CuCa

Ca

S

O

Ca

S

0 1 2 3 4 5 6 7 8 9 10


Spectrum 1

180


ppm of poly[(azepane-1-yl)aspartamide-ran-sodiumaspartate] 20 (DP ≈‎70) as antiscalant

Cu Cu

Cu

Cu

CuCa

CaCa

S

O

Ca

S

0 1 2 3 4 5 6 7 8 9 10


Spectrum 1

181


ppm of poly[(prrolidine-1-yl)aspartamide-ran-sodiumaspartate] 15 (DP ≈‎70) as antiscalant

CuCa

Cu

Cu

Cu

CaCu

Ca

S

O

Ca

S

0 1 2 3 4 5 6 7 8 9 10


Spectrum 1

182

Figure ‎6.12 EDX and SEM images of gypsum formed from 1CB CaCO3 after 50 minutes at 40 oC while using 75 ppm

of poly[(azepane-1-yl)aspartamide-ran-sodiumaspartate] 20 (DP ≈‎190) as antiscalant

CuCuCu

Cu

Cu

Ca

Ca

O

Ca

Ca

0 1 2 3 4 5 6 7 8 9 10


Spectrum 1

183

6.4 Conclusion

In comparing the efficacy of the inhibitors, the performance criterion proposed by Reitz [108]

can

be adopted. In RO desalination, the residence time of the saline water inside the permeators is

less than 15 min. If, according to Reitz [108]

, a scale inhibitor at a certain dose level can keep a

scale-forming salt in solution for at least 15 min (i.e., if it can help achieve an induction period of

15 min), it can be considered as an effective inhibitor at that dose level against that particular

scaling.

The results indicate that almost all of the synthesized green additives are very effective with only

10 ppm dose concentration against precipitation of gypsum at 40 °C and 3CB brine

concentrations except 18 (DP≈70) and 12 (DP≈70). Hydrolyzed SASP-derivatives are more

efficient than unhydrolyzed PSI-derivatives. AzSPASP was found to be the most effective

antiscalant with the induction period of > 3500 min with 10 ppm dose concentration.

10 (DP≈70), 11 (DP≈70),20 (DP≈70) and 15 (DP≈70) can be used as an effective antiscalant for

CaSO4.2H2O even at a dose concentration of only 2.5 ppm in RO plant.

184

7 CHAPTER 7: CONSTRUCTION OF A NOVEL AQUEOUS

TWO-PHASE SYSTEMS WITH PH-RESPONSIVE

DIALLYLAMMONIOPROPANEPHOSPHONATE-alt-

SULFUR DIOXIDE CYCLOCOPOLYMER AND

POLYETHYLENE GLYCOL.

7.1 Introduction

Aqueous two-phase systems (ATPSs) have been considered as an economical and efficient

downstream separation technique which offer many advantages such as low viscosity, little

emulsion formation, absence of organic volatile solvents, high extraction efficiency, low energy

consumption, short process time, reliable scale-up, and a biocompatible environment [277]

The aqueous two-phase system has been extensively studied during the recent years.[278-286]

. The

most commonly used polymer systems are based on poly(ethylene glycol) (PEG) and dextran. In

some cases the polymers have been modified with hydrophobic groups and biospecific ligands

for the affinity partitioning of biomolecules.[75,287-291]

PEG has few functional groups and it is

difficult to attach affinity ligands to it. It would be rewarding to synthesize and introduce novel

polymers, which can form two-phase system and has many functional groups that can be used for

modification.

Poly(N-vinylacetamide) (poly(NVA))-dextran system has been studied [78,292-295]

for protein

(myoglobin) separation. Recently ATPS has been proved to be an alternative to chromatography.

The ATPS screening procedure was applied to a model system composed of PEG4000 and PO4

185

and an industrial separation task. The chosen model systems allowed a reduction of up to 50%

host cell protein (HCP) with a recovery of greater than 95% of the target proteins[296]

. The effect

of pH on the two-phase equilibrium behaviour of an {1-butyl-3-methylimidazolium bromide +

potassium citrate} ATPS in order to obtain information about the salting-out effect produced by

the addition of a kosmotropic salt [ were investigated [297]

. A Liquid-liquid extraction using

ATPSs using different molar masses (ranging from 400 to 4000) of PEG and potassium

phosphate at varying pH from 6 to 11, showed that only high molecular mass PEG in low

concentrations showed pH- dependency. [298]

.

Polyelectrolytes are a worthwhile alternative for polymers in ATPS because of their better

solubility. Polyelectrolytes are polymers that dissociate in aqueous solutions into a charged

polymeric backbone and the corresponding number of mobile counterions. Although the

charging of the polymer backbone increases the solubility of the respective system components

and shrinks (decreases) the region of liquid–liquid immiscibility, enrichment of target

concentrations can be obtained during extraction. The properties of polyelectrolyte solutions

strongly depend upon (1) their degree of neutralization, which is the ratio of charged monomer

groups to the total number of monomers along the polyelectrolyte backbone, (2) the counterions

used for neutralization, e.g. Na+, Li

+, K

+ or NH4

+ etc., (3) the extent of counterion condensation

which determines the ultimate conformation of polyion chain in solution and (4) the molar mass

and concentration of the polyelectrolyte[299]

. The phase behavior of polyelectrolyte–salt ATPS

moreover strongly depends on the choice of the salt. Liquid-liquid equilibria (LLE) model of

ATPS containing poly(acrylic acid) of different degrees of neutralization or poly(vinyl

pyrrolidone), has been studied using perturbed-chain statistical associating fluid theory (PC-

SAFT).[300]

.

186

Ionic polymers including PZs and polyampholytes have the potential to be effective components

in the construction of ATPSs. The ATPSs involving PZs, which seem to mimic biomolecules

like proteins, is expected to impart greater influence in bioseparation involving monomeric

amino acids or proteins. With this in mind, herein we report, the effect of pH and salt

concentration on the phase diagram data of new ATPSs involving pH-responsive dianionic

polyelectrolytes (PZA∙SO2) 2-and PEG. The charge types and their densities on the polymer

chains of the PZA∙SO2 can be controlled by allowing it to equilibrate with the polyzwitterions

(PZA∙SO2) 2 and zwitterionic/anionic polyelectrolyte (ZAPE) 3 under the influence of added

NaOH. Note that ZAPE 3 has an interesting blend of zwitterionic and anionic motifs in the same

repeating unit. The solubility behaviors of the polymers dictate that dianionic polyelectrolyte

(DAPE) 4 could be a promising component for the construction of recycling ATPS since the pH-

responsive polymer can be precipitated at a lower pH value by its conversion to water-insoluble

(PZA∙SO2) 2. Experimental

7.1.1 Materials

The synthesis of the pH- sensitive polymer PZA∙SO2 2 from CPE 1 has been carried out as

described elsewhere (Scheme7−1) [301]

. Polyethylene glycol (PEG) of number average molecular

weight ( nM ) of 35000 was purchased from MERCK-Schuchardt. All solvents used were of

analytical grade.

187

4dianionic polyelectrolyte

(DAPE)

3zwitterionic/anionic

polyelectrolyte (ZAPE)

2polyzwitterionic acid

(PZA)

[ ]n

N

S

O

O

(CH2)3H

P OO

HO

[ ]n

N

S

O

O

(CH2)3H

P OO

Na+ -O

n

N

S

O

O

(CH2)3

(Na+ -O)2P O

NaOH1 equiv.

[ ]

NaOH1 equiv.

1

cationic polyelectrolyte (CPE)

H+/H2OCl

[ ] n

NH

S

O

O

(CH2)3

(EtO)2P O

Scheme ‎7-1

188

7.1.2 Phase compositions and phase diagram of PEG –PZA∙SO2 systems

7.1.2.1 The NMR Method

Various sets of two phase systems were produced by mixing PZA∙SO2 2 and PEG (35000) in

0.3 M as well as 0.6 M NaCl at 1.0,1.5 ad 2.0 equivalent NaOH. The composition of the systems

are described in Tables 7−1,7−2 and 7−3

The mixtures were stirred thoroughly and centrifuged for a period of 15-20 min to make sure a

complete phase separation. After equilibration at 23°C for 24 h, the volume and the density of

the top layers (~1.03 g/cm3) and bottom layers (~1.06 g/cm

3) were measured. The

1H NMR

spectra of both layers were measured after exchanging H2O by D2O (Figure 7.1). The top and

bottom layers were found to be overwhelmingly rich in PEG and PZA∙SO2, respectively. The 1H

NMR spectra of (b) sample from the bottom phase of system 2 of Fig. 7.1 b (Table 7-3) (vide

infra), and (a) sample from top phase of system 3 of Fig. 7.1a (Table 7-3) (vide infra), are

displayed in Fig. 7.1.

189

Figure ‎7.1 1H NMR spectra of ((a)‎Top‎Phase,‎system‎3:‎(PZA∙SO2 2, PEG, 0.3N NaCl, 2.0 equiv. NaOH). b) Bottom

phase,‎system‎2:‎(PZA∙SO2‎2,‎PEG,‎0.3N‎NaCl,‎2.0‎eqiuv.‎NaOH).

The 1H NMR signals for the sixteen protons of PZA∙SO2 2 appeared in the ranges 1.17 – 1.65,

2.45 - 3.05 and 3.10-3.60 ppm while the partially overlapping four-proton singlet at 3.6 were

attributed to the PEG (Fig. 7.1a & 7.1 b)Careful integration of the signals in the ranges 2.25 -

3.05 and 3.10-3.60 ppm revealed their respective areas in a 1.23:1.00 ratio . Note that the

signals in the range 2.45 - 3.05 is free of any overlapping signal and its area (A) is used to

calculate the area (B) under 3.10-3.60 attributed to PZA∙SO2 2 as A×(1.00/1.23). The area (C)

under four-proton overlapping singlet at 3.6 for the PEG was calculated as [D - A×(1.00/1.23)]

a

b

190

where D is the total area in the range 3.10-3.60 ppm belonging to the PEG as well as a part of

PZA∙SO2 2. So, the area for a single H for PZA∙SO2 2 and PEG becomes [A+ B]/16 and C/4,

respectively. The mole ratio of PEG/PZA∙SO2 (i.e. the ratio of area of single H of PEG and

PZA∙SO2) thus becomes:

(1) B]/16 [A

C/4

DAPEofH1forArea

PEG ofH1ofArea

PZA.SOmol

PEG mol

2

1H NMR measurements allowed us to determine the mole ratios. The tie lines were constructed

using the systems in Tables 7−1,7−2 and 7−3. Weight percent of each polymer is determined by

using the Equations 2 and 3 as described in our earlier work [26, 91]

)2(}])/[]([])/[]{([

])/[])([/(05.44/][ 00

tbb

tDAPE

bDAPEPEGDAPEPEGV

DAPEPEGMWDAPEPEGDAPE

.Where, subscript t and b represent top and bottom phase, respectively. [PZA∙SO2] and [PEG]

represent concentration of the repeating units in mmol of repeat unit cm-3

. [PZA∙SO2]0 and

[PEG]0 represent total mass in mg of the polymers and V represents the volume in cm3. Molar

masses of the repeat units of the PZA∙SO2 and PEG were taken as 283.28 and 44.05,

respectively. [PEG]/[PZA∙SO2] represents molar ratio of the polymers as determined by 1H

NMR integration.

The mass of polymer PZA∙SO2 in the bottom phase is then calculated using:

PZA∙SO2b

= [PZA∙SO2b]V

b × 283.28 mg (3)

191

Once one of the polymer concentrations is known in a phase, then the rest of the concentrations

and weight percents of the polymers in the two phases are easily calculated from the known

volume, density and mass of the two phases.

7.1.2.2 Binodals by turbidity method

The turbidity experiments were carried out at laboratory temperature 23°C as described

elsewhere [302-303]

. Thus about 1.5 g of a stirred solution (~10-15 %w/w) of PZA∙SO2 2 (in the

presence of appropriate equivalent of NaOH) in x N NaCl (x = 0.3 or 0.6 N) was titrated with a

known weight of a concentrated solution (~20 %w/w) of the PEG in x N NaCl until the

transparent system turned turbid. Then a known weight of an x N NaCl solution was added until

the system became transparent again. At this point, the composition of the two polymers

corresponds to a point on the binodal curve. The process was repeated to obtain more points

using more PEG to make the mixture turbid followed by addition of x N NaCl to make it

transparent. In order to obtain points on the other end of the binodal, the concentrated solution

of the PEG was titrated with the PZA∙SO2 2 solution using same way as described above.

192

Table ‎7-1 Phase Composition of the [POEa + PZA.SO2b]‎System‎at‎296‎K‎(1.0‎equiv.‎NaOH,‎mNaCl‎of‎0.3‎mol•kg−1)

shown in Figure 7.1

NMR method

System

Total system Top phase Bottom phase Volume

ratioc

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

1 4.45 4.87 8.81 0.383 0.183 9.80 1.06

2 4.05 4.13 7.40 0.456 0.307 8.57 1.19

3 3.71 3.70 6.00 0.803 0.685 7.46 1.33

4 3.11 3.13 4.78 0.854 0.840 6.00 1.33

Turbidity method

System

Binodal data

System

Binodal data

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

a 0.501 7.03 g 3.58 1.36

b 0.832 5.59 h 4.11 1.01

c 1.34 4.42 i 4.69 0.720

d 1.86 3.53 j 5.66 0.507

e 2.33 2.81 k 7.04 0.326

f 2.86 2.24 l 10.1 0.219 apoly(oxyethylene) of molar mass 35.0 kg mol

-1.

bpoly[hydrogen 3-(diallylammonio)

propylphosphonate-alt-sulfur dixide]. cVolume ratio of top and bottom phase.

193


shown in Figure 7.1

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ apoly(oxyethylene) of molar mass 35.0 kg mol

-1.

bpoly[hydrogen 3-(diallylammonio)

propylphosphonate-alt-sulfur dixide]. cVolume ratio of top and bottom phase

NMR method

System

Total system Top phase Bottom phase Volum

e ratioc

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

1 4.62 4.62 9.79 0.246 0.111 8.95 0.944

2 4.10 4.10 7.94 0.305 0.181 8.33 1.09

3 3.67 3.57 7.10 0.430 0.410 6.76 1.00

4 3.12 3.12 5.89 0.470 0.561 5.72 0.971

Turbidity method

System

Binodal data

System

Binodal data

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

a 0.251 7.56 g 2.67 2.11

b 0.619 5.51 h 3.54 1.45

c 1.03 4.39 i 4.21 1.12

d 1.46 3.62 j 6.10 0.47

e 1.87 3.08 k 8.72 0.233

f 2.25 2.59

194


shown in Figure 7.1

NMR method

System

Total system Top phase Bottom phase Volum

e ratioc

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

1 4.65 4.65 10.7 0.137 0.0910 8.36 0.800

2 4.22 4.10 9.37 0.132 0.172 7.38 0.821

3 3.75 3.72 8.04 0.323 0.192 6.87 0.889

4 3.01 3.02 5.90 0.366 0.472 5.42 0.917

Turbidity method

System

Binodal data

System

Binodal data

POE

w ×100

PZA.SO2

w ×100

POE

w ×100

PZA.SO2

w ×100

a 0.251 6.01 g 3.03 1.32

b 0.652 4.39 h 3.69 0.821

c 1.11 3.36 i 4.33 0.612

d 1.73 2.66 j 4.98 0.460

e 2.17 2.15 k 6.53 0.313

f 2.55 1.76 l 7.38 0.242 apoly(oxyethylene) of molar mass 35.0 kg mol

-1.

bpoly[hydrogen 3-

(diallylammonio)propylphosphonate-alt-sulfur dixide]. cVolume ratio of top and bottom

phase.

195

Table ‎7-4 Values for constant parameter A introduced in equation 5 and equation 6 along with the rmsd of the model

from the experimental data of the partition coefficients

7.2 Results and Discussion

7.2.1 Solution properties

PZA∙SO2 2 is a pH-responsive polyelectrolyte that permits several equilibrations involving

ZAPE 3, ZAPE + DAPE 5, DAPE 4, , and PZA 2 (Scheme7−2).

System PZA∙SO2

a POE

b

A1 rmsd A2 rmsd

POE + PZA∙SO2 + 1.0 equiv NaOH -0.352 0.00621 0.441 0.929



apoly[PZA-alt-sulfur dioxide].

bpoly(oxyethylene) of molar mass 35.0 kg mol

-1.

196

4dianionic polyelectrolyte

(DAPE)

NaOH2 equiv.

3zwitterionic/anionic

polyelectrolyte (ZAPE)

NaOH1 equiv.

2polyzwitterionic acid

(PZA)

[ ]n

N

S

O

O

(CH2)3H

P OO

HO

[ ]n

N

S

O

O

(CH2)3H

P OO

Na+ -O

n

N

S

O

O

(CH2)3

(Na+ -O)2P O

0.5n

N

S

O

O

(CH2)3

(Na+ -O)2P O

N

S

O

O

(CH2)3H

P OO

Na+ -O

NaOH0.5 equiv.

HCl0.5 equiv.

NaOH0.5 equiv.

HCl1 equiv.

HCl2 equiv.

[ ]

[ ] [ ]0.5n

ZAPE+DAPE5

Scheme ‎7-2

The dominance of a particular form would depend on the pH of the medium. Note that the The

type of charges and their densities on the polymer backbone can be controlled by addition of

NaOH or HCl. In the presence of 0, 1, 1.5, and 2 equivalents of NaOH, the dominant form in the

equilibrations is expected to be PZA∙SO2 2, ZAPE 3, ZAPE+DAPE 5, and DAPE 4, respectively

197

(Scheme 7−3). Note that all the forms are soluble in salt-free water except PZA∙SO2 2, in which

the zwitterionic interactions are so strong which requires high salt concentration to disrupt the

intra- and interchain attractive interactions and permit its water solubility. PZA∙SO2 2 upon

addition of 1 equiv NaOH gives water-soluble ZAPE 3. One of the important advantage of

having PZA∙SO2 as a component in an ATPS is that it can be used as a water-soluble polymer in

the form of 3, 4 and 5 above a certain minimum pH and below which it can be recycled by

precipitating out in the form of water-insoluble PZA∙SO2 2. The solubility behavior (as presented

above) and its relationship with the hydrodynamic volume of a polymer chain can be rationalized

using eq 4. The screening of the attractive polyampholytic interactions between opposite charges

and repulsive Coulombic interactions between similar charges can be described

mathematically[304-307]

by the first and second term of eq 4, respectively:

)4(f4π)π(f

- *v2

2

B

2

B

SS

II

where v* is the electrostatic excluded volume, IB is the Bjerrum length, f is the total fraction of

charged monomers, f is the charge imbalance, and S is the Debye-Huckel screening parameter.

The solution behavior of ionic polymers with or without charge symmetry is then described by

v*: a negative and a positive excluded volume implies contraction and expansion of a polymer

chain, respectively. For a electroneutral (±)PZA∙SO2 2, the solution behavior is described by the

screening of the attractive polyampholytic interactions since the second term of eq. 4 becomes

zero as a result of f = 0. The negative v* electrostatic excluded volume indicates contraction to

a collapsed polymer chain. The electroneutrality of (±)PZA∙SO2 2 cannot be maintained in the

presence of added salt NaCl; it acquires an overall anionic charge since the cationic nitrogens are

198

more effectively screened by Cl- ions, than the anionic PO3

- by the Na

+. As a result, the presence

of NaCl makes v* value a less negative thus helping the polymer coil to expand thereby resulting

in increased solubility of the polymer.

7.2.2 Effect of NaCl and NaOH on the binodal of PZA∙SO2 2-PEG ATPS

The phase diagrams of PZA∙SO2 2-PEG-H2O systems are shown in Fig 7.2. In the phase

diagrams, the %w/w of the polymer rich in the top and bottom phase is assigned the y- and x-

axis, respectively. The PEG and PZA∙SO2 preferred to stay at the top and bottom phase,

respectively. The tie lines in the phase diagrams for each total system of composition Atotal were

constructed by 1H

NMR method which is used to determine the compositions Atop and Abottom of

the polymers in equilibrium in the top and bottom phases, respectively. The tie lines are helpful

in the construction of ATPS with suitable volume ratio of the top and bottom phases as

determined by the ratio of the tie line lengths of Atotal-Abot and Atotal-Atop. The binodal curves

were obtained by the turbidity method. The experimental data are shown in Tables 7−1,7−2 and

7−3

199

Figure ‎7.2 Phase‎diagram‎(■‎and‎□‎represent‎data‎obtained‎by‎respective‎(NMR‎and‎turbidity‎method)‎of‎‎PZA.SO2

treated with: a) 1.0 equvi NaOH; b) 1.5 equvi NaOH; c) 2 equiv. NaOH)-PEG-Water (0.3 N NaCl) at

23oC.; d) effect of different pH on binodal plane.

0

2

4

6

8

10

12

0 2 4 6 8 10

100 w

PE

G

100 wPZA.SO2

(%w/w)

0

2

4

6

8

10

12

0 2 4 6 8 10

100 w

PO

E

100 wPZA.SO2

0

1

2

3

4

0 2 4 6 8 10

100 w

PO

E

100 wPZA.SO2

Turbidity method NMR method

1.0 equvi NaOH; 0.3M NaCl

0

2

4

6

8

10

12

0 2 4 6 8 10

10

0 w

PO

E

100 wPZA.SO2

■1.0 equvi NaOH □1.5 equvi NaOH

►2.0 equvi NaOH 0.3M NaCl

a b

c d





0

1

2

3

4

0 2 4 6 8 10

10

0 w

PE

G

100 wPZA.SO2

e

200

The binodals ascertain the segregative phase separation behavior of the polymers, and their

symmetrical shape imply that the two polymers may have very similar hydrodynamic volumes.

The phase formation happening at total polymer concentrations of below 10 %w/w, could be

useful from an industrial point of view. The effect of salt concentration on the binodals is shown

in Fig. 7.2d. The binodal curves are shifted downward with the increase in concentration of

NaCl. The increase in the salt concentration leads to a decrease in electrostatic repulsion between

the poly-electrolyte chains[308-310]

leading to a compact coiled structure (Fig. 7.3 For PZA∙SO2 2,

addition of salt is thus expected to decrease the hydrodynamic volume of the polymer chain,

which in turn makes it less compatible with the PEG thereby requiring lesser amounts of

polymers for phase separation to occur. Changing the NaCl concentration from 0.3 N to 0.6 N,

leads to a greater contraction of polymer chain of PZA∙SO2 2.

The effects of NaCl concentration and the types of backbone charges (depending on the amount

of added NaOH) on the binodal curves are displayed in Fig. 7.2. The binodal curves are also

shifted downward with the increase in concentration of NaCl from 0.3 N to 0.6 N in the presence

of 1.0, 1.5 or 2.0 equivalent of NaOH (Fig. 7.3e). Note that the ZAPE 3 (~33% negative charge)

in the presence of 0.5 and 1 equivalent NaOH becomes DAPE/ZAPE (=)/(± −) 5 and DAPE (=)

4 with a respective charge imbalance (f) of 0.60 and 1.0 in favor of the negative charges. The

size of the polymer chain increases with the increase in f and leads to lesser size-mismatch in

the case of DAPE 4 thereby making it the more compatible with the PEG. Since all three species

(i.e. 3, 4 and 5) have excess negative charges in the polymer backbone, the addition of added salt

(NaCl) has thus demonstrated polyelectrolyte effect (Fig. 7.3) by decreasing the hydrodynamic

volume of the polymers.

201

Figure ‎7.3 Effect of added salt on the conformation of polyelectrolytes and polyzwitterions

202

Figure ‎7.4 Effect of 0.5 ad 1.0 equivalent NaOH on ZAPE 3

7.2.3 The Correlation of the Phase Diagrams Using the Method of Diamond and Hsu

The consistency of the tie-lines of the [PZA∙SO2 4-PEG-H2O (NaCl)] systems was checked using

the following correlation developed by Diamond & Hsu [311]

based on Flory- Huggins theory:

LnK1= A1(w1’’- w1’) (5)

And

LnK2 = A2(w2’’ – w2’) (6)

where w'' and w' are the polymer weight percent in the top and bottom phase, respectively, the

slopes A1 and A2 are functions of the polymer molecular weight and the interactions between the

polymers and water, K1 and K2 represent the partition coefficient (Ct/Cb) of the polymer between

the top and bottom phase, and the subscripts 1 and 2 represent polymer 1 (PZA∙SO2 2) and

ZAPE DAPE ZAPE + DAPE

203

polymer 2 (PEG). Straight line plots for the correlation results ascertain the satisfactory

representation of the phase behaviour by this model (Figure 7.5).

Figure ‎7.5 Correlation of the Phase diagram of PZA.SO2 (NaOH)-PEO-H2O (NaCl) systems using the Diamond and

Hsu method : using the tie lie data of (a) Figure1, (b) Figure 2, and (c) Figure 3

-6

-4

-2

0

2

4

6

0 2 4 6 8 10Ln

K

(w" - w')

-6

-4

-2

0

2

4

6

0 2 4 6 8 10 12Ln

K

(w" - w')

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0 2 4 6 8 10 12

Ln

K

(w" - w')

(a)

(b)

(c)

204

7.3 Conclusions

In this work a pH-responsive polyaminophosphonate PZA∙SO2 2 was used in the construction of

aqueous two-phase systems with PEG. The effect of pH and salt on the binodal curves was

investigated. The two polymers were found to form ATPS at low concentrations, where the

addition of NaOH changed the charge types and their densities on the polymer chains. The

increasing concentration of NaCl shifted the binodals downward thereby requiring lesser

concentration of the polymers to form ATPS. One of the most interesting aspects of PZA∙SO2 2

is its almost zero solubility in water. The solubility behavior thus makes it a suitable component

for the construction of ATPSs where the polymer can be effectively removed and recycled. The

aminopropylphosphonate residues in 4 and 3 mimic biomolecules like proteins, and as such the

ATPSs may be used in bioseparation involving monomeric amino acids or proteins. Variable

charge densities in the polymer backbone may be exploited in selecting and separating certain

proteins in the newly developed ATPSs.

205

References

[1] Gill, J. S. (1999). Desalination, 124, 43-50.

[2] Anton, P.; Laschewsky, A. Makromol Chem 1993, 194, 601-624.

[3] Wielema, T. A.; Engberts, J. B. F. N. Eur Polym J 1987, 23, 947-950.

[4] Ali, S. A.; Rasheed, A. Polymer 1999, 40, 6849-6857.

[5] Ali, M. M.; Perzanowski, H. P.; Ali, S.A. Polymer 2000, 41, 5591-5600.

[6] Albertsson, P. A. Partition of cell particle and macromolecules; John Wiley: New

York, 1986.

[7] Walter, H.; Brookes, D. E.; Fisher, D. Partitioning in Aqueous Two-Phase systems:

Theory, Methods, Uses and Application to Bio-technology; Academic Press: Orlando,

1989.

[8] Johansson, H. O.; Magaldi, F. M.; Feitosa, E.; Pessoa J. A., J. Chromatogr. A. 2008,

1178, 145-153.

[9] Su, C. K.; Chiang, B. H.. Process Biochem. 2006, 41, 257-263.

[10] Benavides, J.; Aguilar, O.; Lapizco-Encinas, B. H.; Rito-Palomares, M., Chem. Eng.

Technol. 2008, 31, 838–845.

[11] Andrews, B. A.; Schmidt, A. S.; Asenjo, J. A., Biotechnol. Bioeng. 2005, 90(3), 380-

390.

[12] Albertsson, P. A.; Tjerneld, F., Methods Enzymol. 1994, 228, 3-13.

[13] Dissing, U.; Mattiasson, B., Biotechnol. Appl. Biochem. 1993, 17, 15-21.

[14] Bergfeldt K; Piculell L; Tjerneld F., Macromolecules 1995, 28, 3360-3370.

[15] Svensson, M.; Linse, P.; Tjerneld, F., Macromolecules 1995, 28, 3597-3603.

[16] Liu J.; Ma Y.; Xu T.; Shao G.; J. Hazard. Mater. 178 (2010) 1021-9.

[17] Vinodh R.; Padmavathi R.; Sangeetha D., Desalination. 267 (2011) 267-276.

[18] Camci-Unal G.; Pohl N.L.B., J. Chem. Eng. Data. 55 (2010) 1117-1121.

[19] . Kiefer R.; Höll W.H., Ind. Eng. Chem. 40 (2001) 4570-4576.

[20] . Güçlü G.; Gürdağ G.; Özgümüş S., J. Appl. Polym. Sci. 90 (2003) 2034-2039.

206

[21] . Kesenci K.; Say R, A., Eur. Polym. J. 38 (2002) 1443-1448.

[22] Geckeler K. E., Pure. Appl. Chem. 73 (2001) 129-136.

[23] Hong W.U.; In Y.J.; Uo M.L.; Shuping B.I., Wine , and Rice, Anal. Chem. 23 (2007)

1109-1112.

[24] Shahtaheri S.J.; Khadem M.; Golbabaei F.; Rahimi-Froushan A.; Ganjali M.R., Int.

J. Occup. Saf. Ergo. 13(2007) 137-145.

[25] Kudaibergenov, S.; Jaeger, W.; Laschewsky, A. Advances in Polymer Science 2006,

201, 157-224.

[26] Singh, P. K.; Singh, V. K.; Singh, M. e-Polymers 2007, 030, 1-34

[27] Salamone, J. C.; Volksen, W.; Olson, A. P.; Israel, S. C. Polymer 1978, 19, 1157-

1162.

[28] Skouri, M.; Munch, J. P.; Candau, S. J.; Nyret, S.; Candau, F. Macromolecules 1994,

27, 69-76.

[29] Butler, G. B. Cyclopolymerization and cyclocopolymerization; Marcel Dekker: New

York, 1992.

[30] Hoover M. F., J. Macromol. Sci. (A) 1970, 4, 1327

[31] Chemical Economics Handbook, pp. 581-10111, 581-50221, 582-1012D, Stanford

Research Institute, Menlo Park, CA 1983

[32] Butler, G. B., Acc. Chem. Res. 1982, 15, 370 .

[33] Johns S. R.; Willing R. I.; Middleton S.; Ong A. K., J. Macromol. Sci., Chem A,

1976, 10, 875

[34] J. E. Lancaster, L. Baccei, and H. Panzer, J Polym. Sci. Polym. Lett. Ed., 1976, 14,

549

[35] R. M. Ottenbrite and W. S. Ryan, Jr., Ind. Eng. Chem. Prod. Res. Develop., 1980,

19, 528

[36] S. Harada, and M. Katayama, Makromol. Chem., 1966, 90, 177.

[37] S. A. Ali, S. Z. Ahmad and E. Z. Hamad, J. Appl. Poly. Sci., 1996, 61, 1077

[38] S. A. Ali, M. I. M. Wazeer, S. Zaka Ahmed, J. Appl. Poly. Sci., 1998, 69, 1329-1334

[39] S. A. Ali, S. Z. Ahmed, E. Z. Hamad and M. I. M. Wazeer, Polymer, 1997, 38,

3385-3393

207

[40] S. A. Ali, A. Rasheed and M. I. M. Wazeer, Polymer, 1999, 40, 2439-2446

[41] S. A. Ali and Aal-e-Ali, Polymer, 2001, 42, 7961-7970

[42] H. A. Al-Muallem, M. I. M. Wazeer and S. A. Ali, Polymer, 2002, 43, 4285-4295

[43] S. A. Ali, M. A. J. Mazumder and H. A. Al-Muallem, J. Poly. Sci., Part A, 2003,

41, 172-184

[44] M. A. J. Mazumder, Y. Umar, S. A. Ali, Polymer, 2004, 45, 125-132

[45] H.A. Al-Muallem, M. I. M. Wazeer and S. A. Ali, Polymer, 2002, 43, 1041-1050

[46] S. A. Ali, H. A. Al-Muallem and M.A. J. Mazumdar, Polymer, 2003, 44, 1671-1679.

[47] J. C. Salamone, C. C. Tsai, A.P. Olson, A. C. Watterson, Adv. Chem. Ser., 1980,

187, 337

[48] D. N. Schulz, D. G. Peiffer, P. K. Agarwal, J. J. Kaladas, L.Soni, H. Handwerker and

R. T. Gardener, Polymer, 1986, 27, 1734

[49] E. Volpert, J. Selb, F. Candau, Macromolecules, 1996, 29, 1452

[50] F. Candau, A. Ohlmacher, J. P. Munch, S. J. Candau, Rev. Institute Franscais du

Petrole, 1997, 52, 133-137

[51] C. S. Patrikios, W. R. Hertler, T. A. Hatton, Biotechnology and Bioengineering,

1994, 44, 1031

[52] C. L. McCormic.; Bock J.; Schulz D. N, in Encyclopedia of Polymer Science and

Engineering, 2nd ed., John Wiley & Sons, Inc. New York, vol. 1989, 17, pp 730-784

[53] C. S. Patrikios, W. R. Hertler, T. A. Hatton, Amer. Chem. Soc. 1994, 207, 161,

[54] C. J. Jang, W. R. Hertler, T. A. Hatton, ACS Symposium Series, 1994, 548, 257

[55] J. E. Booth, H. G. Flock, M. F. Hoover, J. Macromol. Sci.-Chem. 1970, 4, 1419,

[56] J. E. Glass, Water soluble Polymers, Adv. Chem. Ser. 213 (EOR Appl. Water Sol

Poly.).

[57] F. Rullens, N. Deligne, A. Laschewsky, M. Devillers, J. Materials Chemistry, ,

2005, 15(16), 1668-1676.

[58] S. E. Kudaibergenov, Adv. Poly. Sci., 1999, 144 115Springer-Verlag.

[59] D. J. Liaw, C. C. Huang, E. T. Kang, Curr. Trends. Polym. Sci. 1999., 4, 117,

[60] P. Mary, D. D. Bendejacq, J. Phys. Chem. B, 2008, 112, 2299-2310

208

[61] S. Kudaibergenov, W. Jaeger, A. Laschewsky, Advances in Polymer Science 2006,

201 157-224

[62] A. Ohsugi, H. Furukawa, A. Kakugo, Y. Osada, J. P. Gong, Macromol. Rapid

Commun. 2006, 27, 1242-1246

[63] P. Albertsson, Partition of Cell particles and Macromolecules, 3rd Ed. Wiley, N.Y.

1986

[64] H. Walter, D. E. Brooks and D. Fischer (eds), Partitioning in Aqueous Two-Phase

systems, Academic Press, New York 1985.

[65] N. L. Abbot, D. Blankschtein and T. A. Hatton, Bioseparation, 1990, 1, 191

[66] P. A. Albertson and F. Tjerneld, Methods Enzymol., 1994, 228, 3

[67] U. Dissing and B. Mattiasson, Biotechnol. Appl. Biochem., 1993, 17, 15

[68] K. Begfeld, L. Piculell, and F. Tjerneld, Macromolecules, 1995, 28, 3360

[69] M. Svensson, P. Linse, and F. Tjerneld, Macromolecules, 1995, 28, 3597

[70] M. Lu, P. A. Albertsson,G. Johansson, and F.Tjerneld, J. Chromatogr., A., 1994,

668, 215

[71] U. Sivars, K. Bergfeldt, L.Pictulell, and F. Tjerneld, J. Chromatography., B., 1996,

680, 43

[72] G. Birkenmeier and M. Kunath, J. Chromatogr., B, 1996, 680, 97

[73] M. Akashi, S. Nakono, and A. Kishida, J. Polym. Sci., Part A, Polym. Chem. Ed.,

1996, 34, 301

[74] J. S. Hong, T. Nakahara, H. maeda, Y. Kikunaga, A. Kishida, and M. Akashi,

Colloid Polym. Sci., 1996, 8, 274

[75] E. J. Hamad, W. Ijaz, Sk. A. Ali, and M. A. Hastaglu, Biotechnol. Prog., 1996, 12,

173

[76] Xiao-ge Ba, Jin-xing Lin, Zhao-fa Qiu, Huaxue Shijie 2007, 48(4), 240-242, 251,.

[77] H. A. Al-Muallem, M. I. M. Wazeer and S. A. Ali, Polymer, 2002, 43, 1041-1050.

[78] S. A Ali, H A. Al-Muallem and M I. M. Wazeer, J. Poly. Sci., Part A, Polym Chem,

2002, 40, 2464-2477

[79] S. M. Waziri, B. F. Abu-Sharkh and S. A. Ali, Fluid Phase Equilibria, 2003. 205,

275-290

209

[80] M. Waziri, B. F. Abu-Sharkh and S. A. Ali, Biotechnology Progress, 2004, 20(2),

526-532..

[81] Patricio, P. d. R.; Mesquita, M. C.; Mendes da Silva, L. H.; Hespanhol da Silva,

M.C. J Hazard Mater 2011, 193, 311-318.

[82] Lacerda, V. G.; Mageste, A. B.; Santos, I. J. B.; Mendes da Silva, L. H.; Hespanhol

da Silva, M. do C. J Power Sources 2009, 193, 908-913.

[83] Bulgariu, L.; Bulgariu, D. Sep Purif Technol 2011, 80, 620-625.

[84] Bulgariu, L.; Bulgariu, D. J Chromatogr A 2008, 1196-1197, 117-124.

[85] Aguinaga-Diaz, P. A.; Guzman, R. Z., Sep Sci Technol 1996, 31, 1483-1499.

[86] Al-Shammiri, M., M. Safar and M. Al-Dawas , Desalination 2000, 128, No. 1, 1-16.

[87] Spiegler, KS; Laird, A , Principles of Desalination; 1980, 2nd ed

[88] Logan, D. and. Walker J.L.1982. Scale Control in High Temperature MSF

Evaporators with Concurrent Acid and Inhibitor Treatment, Calgon Corporation,

Pittsburgh, Pennsylvania.

[89] Harris, A.. Desalination Technology, Ed. A. Porteous, 1983, pp. 44-48.

[90] Dalvi, G. A., Mohammad, N. M. K. Al-Sulami, S. Al-Radwan, R. and Sahul, K.

1999. Technical Report No. TR 3803/APP 95001, SWCC.

[91] Matsumura, S. Mada, S. Yoshikawa, S. . Polymer Mater. Sci. Eng 1990. 62:984.

[92] Ouchi, T. Shiratani, M. Jinno, M. Hirao, M. Ohya, Y.. Macromol. Chem., Rapid

Commun. 1993, 14:825.

[93] Hayashi, T. Iwatsuki, M.. Biopolymers. 1990, 29:549.

[94] Jain, G. L., Ray, A. R.. Macromol. Chem. 1981, 182:2557.

[95] Nakato, T. Kusono, A. Kakuchi, T.. J. Polym. Sci.: Part A: Polym. Chem. 2000

38:117-122.

[96] Zarges, W. Groth, T. Joentgen, W. Groschl, A..USP 6, 2001, 187,195 B1, Feb 13.

[97] Braun, G. Hater, W. Kolk, C. zum. Dupoiron, C. Harrer, T. Götz, T., Desalination,

2010, 250:982-984.

[98] Zuback, J. E. 2009. Desalination of water containing high silica content, PCT Int.

Appl., WO 2009102442 A1 20090820.

[99] Rajan, K. S. Murase, J. Martell, A. E.. New multidentate ligands. VII. 1969

javascript:;

javascript:;

210

[100] Westerback, S. J. Martell, A. E. Nature 1956. 178, 321-322.

[101] Yamashoji, Y. Matsushita, T. Shono, T.. Technol Rep Osaka Univ 1985. 35 (1800-

1818):331-337.

[102] Armitage, , B. A.; Bennet, D. E.; Lamparski, H. G.; O’Brien, D. F. Adv polym Sci

1996, 126, 54.

[103] Haruta, M.; Kageno, K.; Soeta, M.; Harada, S. Jpn Kokai Tokkyo Koho 1975,

50072987 19750616.

[104] Elliot, M.N. , Desalination, 1970, 8, 231-236.

[105] Leung, W. H. and G. H. Nancollas., J. Cryst. Growth, 1978 44, pp. 163-167.

[106] Busch, B. D., U.S. Patent July 1981 4,279,768, 21 - C.A.

[107] Addadi, L., S. Weinstein, E. Gati, I. Weissbuck and M. Lahov. J. Am. Chem. Soc.,

1982 104, 4610-4617

[108] Reitz, R. L.., Proceedings of the 12th Water Supply Improvement Association, 1984

vol 1, Session IV, pp. 1-26.

[109] Butt,F.H., F. Rahman, and U. Baduruthamal 1997. Vol. 109, pp. 323-332.

[110] Amjad, Z. Desalination, 1985, v. 54, pp. 263-276.

[111] Smith, A.; Logan, D.; Nehus, H. & Delitsky, M.Desalination, Elsevier, 1985, 54,

277-289

[112] M. Oner et al. Journal of Crystal Growth 186 1998 427Ð, 437

[113] Elimelech, M.; Zhu, X.; Childress, A. & Hong, S. Journal of membrane science,

Elsevier, 1997, 127, 101-109

[114] M.G. Lioliou Journal of Colloid and Interface Science 2006 303 164–170

[115] Reidelsberger, K.; Jaeger, W. Designed Monomers and Polymers 1998, 1, 387-407

[116] Ali, S. A.; Abu-Thabit, N. Y.; Al-Muallem, H. A. J Polym Sci Part A: Polym chem

2010, 48, 5693-5703.

[117] Westerback, S.; Martell, A. E. Nature 1956, 178, 321.

[118] Yamashoji, Y.; Matsushita, T.; Shono, T. Technol Rep Osaka Univ 1985, 35, 331.

[119] Singh PK, Singh VK, Singh M. e-Polymers 2007;030:1-34.

[120] Lowe AB, McCormick CL. Chem Rev 2002;102:4177-4189.

211

[121] Waziri M, Abu-Sharkh BF, Ali SA. Biotechnol Progr 2004;20:526-532.

[122] Lee W.F, Lee, C.H. Polymer 1997;38:971-9.

[123] Butler GB. Cyclopolymerization and Cyclocopolymerization. New York: Marcel

Dekker, 1992

[124] Ali SA, Mazumder MAJ, Al-Muallem HA. J Polym Sci Part A: Poly Chem 2003;

41:172-84.

[125] Ali SA, Al-Muallem HA, Mazumder MAJ. Polymer 2003;44:1671-79.

[126] Umar Y, Abu-Sharkh BF, Ali SA. Polymer 2005;46:10709-10717.

[127] Ali SA, Umar Y, Abu-Sharkh BF, Al-Muallem HA. J Pol Sci Part A: Poly Chem

2006;44:5480-5494.

[128] Nakaya T, Li YL. Prog Polym Sci 1999; 24:143.

[129] Mou L, Singh G, Nicholson JW. Chem Commun 2000;5:345-346.

[130] Perrin R, Elomaa M, Jannasch P. Macromolecules 2009;42:5146-5154.

[131] Lafitte B, Jannasch P. J Polym Sci Part A: Poly Chem 2005;43:273-286.

[132] Westerback S, Martell AE. Nature 1956;178:321

[133] Yamashoji Y, Matsushita T, Shono T. Technol Rep Osaka Univ 1985;35:331.

[134] Al-Muallem HA, Wazeer MIM, Ali SA. Polymer 2002;43:4285-4295.

[135] Felty WK. J Chem Educ 1978;55:576.

[136] Barbucci R, Casolaro M, Ferruti P, Barone V, Lelji F, Oliva L. Macromolecules

1981;14:1203.

[137] Barbucci R, Casolaro M, Nocentini M, Correzzi S, Ferruti P, Barone V.

Macromolecules 1986;19:37.

[138] Pike RM, Cohen RA. J Polym Sci 1960;44:531-8.

[139] Wilema TA, Engberts JBFN. Eur Polym J 1990;26:415-421.

[140] Ali SA, Aal-e-Ali. Polymer 2001;42:7961-7970.

[141] Walsh DJ, Cheng GL. Polymer 1984;25:499.

[142] Monroy Soto, Galin VM. J. C. Polymer 1984;25:254-262.

212

[143] Schultz DN, Peiffer DG, Agarwal PK, Larabee J, Kaladas JJ, Soni L, Handwerker H,

Gardner RT. Polymer 1986;27:1734-42.

[144] Butler GB, Angelo RJ. J Am Chem Soc 1957;79:3128-31.

[145] Ali SA, Ahmed SZ, Wazeer MIM, Hamad EZ. Polymer 1997;38:3385-93.

[146] Lancaster JE, Baccei L, Panzer HP. J Polym Sci Part C: Polym Lett 1976;14:549-54.

[147] Butler GB. Acc Chem Res 1982;15:370.

[148] Vynck VD, Goethals E., J. Macromol Rapid Commun 1997;18:149.

[149] Ali SA, Rasheed A. Polymer 1999;40:6849-57.

[150] Vorobeva AI, Vasileva EV, Gaisina KA, Puzin YI, Leplyanin GV. Polym Sci, Ser A

1996;38:1077-80.

[151] Salamone JC, Volksen W, Olson AP, Israel SC. Polymer 1978;19:1157-62.

[152] Barbucci, R.; Casolaro, M. ; Ferruti, P. ; Nocentini, M. Macromolecules 1986;

19:1856.

[153] G. B. Butler, Cyclopolymerization and cyclocopolymerization, Marcel Dekker, New

York (1992).

[154] P. K. Singh, V. K. Singh, M. Singh, e-Polymers, 030, 1-34 (2007).

[155] W. Jaeger, J. Bohrisch, A. Laschewsky, Prog. Polym. Sci., 35, 511–77 (2010).

[156] N. Y. Abu-Thabit, H. A. Al-Muallem, S.A. Ali, J. Appl. Polym. Sci., 120, 3662-3673

(2011).

[157] G. B. Butler, J. Polym. Sci., A: Polym. Chem., 38, 3451-3461 (2000).

[158] F. C. McGrew, J. Chem. Ed., 35, 178-186 (1958).

[159] S. K.; Tripathy, J. Kumar, H. S. Nalwa, editors: Handbook of polyelectrolytes and

their applications, vols. 1–3. Stevenson Ranch, CA: American Scientific Publ.,

(2003).

[160] H. Dautzenberg, W. Jaeger, J. Koetz, B. Philipp, C. Seidel, D. Stscherbina,

Polyelectrolytes—formation, characterization, and application, Hanser Publishers,

Munich, Vienna, New York (1994).

[161] S. A. Ali, M. A. J. Mazumder and H. A. Al-Muallem, J. Polym. Sci., A: Polym.

Chem., 41, 172-184 (2003).

[162] H. A. Al-Muallem, M. I. M. Wazeer, S. A. Ali, Polymer, 43, 4285-4295 (2002).

213

[163] O. C. S. Al-Hamouz and S. A. Ali, J. Polym. Sci., A: Polym. Chem., 50, 3580 (2012)

[164] A. V. Dobrynin, M. Rubinstein, J. Phys. II , 5, 677-695 (1995).

[165] P. G. Higgs, J. F. Joany, J. Chem. Phys., 94, 1543-54 (1991).

[166] H. Ohno, K. Ito, Chem. Lett., 751-752 (1998) .

[167] M. Yoshizawa, H. Ohno, Chem. Lett., 889-890 (1999).

[168] G.Y.N. Chan, T.C. Hughes, K.M. McClean, G.A. McFarland, X. Nguyen, S.J.

Wilkie, G. Johnson, Biomaterial s, 27, 1287-1295 (2006) .

[169] Y.-Z. You, C.-Y. Hong, C.-Y. Pan, Nanotechnology, 17, 2350-2354 (2006).

[170] S. E. Kudaibergenov, Polyampholytes: Synthesis, Characterization, and Application,

Plenum Corporation, New York (2002).

[171] J. C. Salamone, W. C. Rice,.; H. F. Mark, N. M. Bikales, C. G. Overberger, G.

Menges, J. I. Kroschwitz, In Encycl. Polym. Sci. Eng Eds., John Wiley & Sons, Inc.,

New York, Vol. 11, 514-530 (1987) .

[172] D. Filippini, P. Asberg, P. Nilsson, O. Inganas, I. Lundstrom, Sensors and Actuators

B: Chemica, 113, 410-418 (2005).

[173] B. A. Armitage, D. E. Bennet, H. G. Lamparski, D. F. O’Brien, Adv. Polym. Sci.,

126, 54 (1996).

[174] N. Y. Abu-Thabit, I. W. Kazi, H. A. Al-Muallem, S. A. Ali, Eur. Polym. J., 47,

1113-1123 (2011).

[175] S. A. Ali and O. C. S. Al-Hamouz, Polymer, 53, 3368-3377 (2012).

[176] B. Akgun, E. Savci, D. Avci, J. Polym. Sci. A: Polym. Chem., 50, 801–810 (2012).

[177] Z. S. Bilgici, O. D. Ordu, M. Isik, D. Avci, J. Polym. Sci. A: Polym. Chem., 49,

5042–5048 (2011).

[178] Y. Yamashoji, T. Matsushita, T. Shono, Technol. Rep. Osaka Univ., 35, 331 (1985).

[179] R. J. Davey, The Role of Additives in Precipitation Processes, Industrial

Crystallization 81, Eds. S. J. Jancic and E. J. de Jong, North-Holland Publishing Co.,

123-135 (1982).

[180] F. H. Butt, F. Rahman, U. Baduruthamal, Desalination, 103, 189-198, 1995.

[181] R. M. Pike, R. A. Cohen, J. Polym. Sci., 44, 531-8 (1960).

214

[182] J. C. Salamone, W. Volksen, A. P. Olson, S. C. Israel, Polymer, 19, 1157-1162

(1978).

[183] G. B. Butler, R. J. Angelo, J. Am. Chem. Soc., 79, 3128 (1957).

[184] S. A. Ali, S. Z. Ahmed, M. I. M. Wazeer, E. Z. Hamad, Polymer, 38, 3385 (1997) .

[185] J. E. Lancaster, L. Baccei, H. P. Panzer, J. Polym. Sci . Polym. Lett. Edn., 14, 549

(1976).

[186] G. B. Butler, Acc. Chem. Res., 15, 370 (1982).

[187] V. D. Vynck, E. J. Goethals, Macromol. Rapid Commun., 18, 149 (1997).

[188] K.S. Spiegler, and A.D.K. Laird, Principles of Desalination, Part A, 2nd edn.,

Academic Press, New York (1980).

[189] H. David. S. Hilla, S. Alexander, Ind. Eng. Chem. Res., 50, 7601–7607 (2011).

[190] Butler GB, J Polym Sci A: Polym Chem 38:3451-3461 (2000).

[191] McGrew FC, J Chem Ed 35:178-186 (1958).

[192] Butler GB, Cyclopolymerization and cyclocopolymerization, Marcel Dekker, New

York (1992).

[193] Singh PK, Singh VK, Singh M, e-Polymers 030:1-34 (2007).

[194] Jaeger W, Bohrisch J, Laschewsky A, Prog Polym Sci 35:511–577 (2010).

[195] Abu-Thabit NY, Al-Muallem HA, Ali SA, J Appl Polym Sci 120:3662-3673 (2011).

[196] Ali SA, Mazumder MAJ, Al-Muallem HA, J Polym Sci A: Polym Chem 41:172-

184 (2003).

[197] Al-Muallem HA, Wazeer MIM, Ali SA, Polymer, 43:4285-4295 (2002).

[198] Ali SA, Al-Hamouz OCS, Polymer 53:3368-3377 (2012).

[199] Akgun B. Savci E, Avci D, J Polym Sci A: Polym Chem 50:801–810 (2012).

[200] Bilgici ZS, Ordu OD, Isik M, Avci D, J Polym Sci A: Polym Chem 49:5042–5048

(2011).

[201] Ali SA, Al-Muallem HA, Mazumder MAJ, Polymer 44:1671-1679 (2003).

[202] Tripathy SK, Kumar J, Nalwa HS, editors: Handbook of polyelectrolytes and their

applications, vols. 1–3. Stevenson Ranch, CA: American Scientific Publ, (2003).

215

[203] Dautzenberg H, Jaeger W, Koetz J, Philipp B, Seidel C, Stscherbina D,

Polyelectrolytes—formation, characterization, and application, Hanser Publishers,

Munich, Vienna, New York (1994).

[204] Salamone JC, Rice WC,; Mark HF, Bikales NM, Overberger CG, Menges G,

Kroschwitz JI, In Encycl Polym Sci Eng Eds, John Wiley & Sons, Inc., New York,

Vol. 11, 514-530 (1987).

[205] Filippini D, Asberg P, Nilsson P, Inganas O, Lundstrom I, Sensors and Actuators B:

Chemica 113:410-418 (2005).

[206] Ohno H, Ito K, Chem Lett 751-752 (1998).

[207] Yoshizawa M, Ohno H, Chem Lett 889-890 (1999).

[208] Salamone JC, Rice WC,. H. F. Mark, N. M. Bikales, C. G. Overberger, G. Menges, J.

I. Kroschwitz, In Encycl. Polym. Sci. Eng Eds., John Wiley & Sons, Inc., New York,

Vol. 11, 514-530 (1987) .

[209] Wielema TA, Engberts JBFN, Eur Polym J 23:947-950 (1987).

[210] Dobrynin AV, Rubinstein M, J Phys II 5:677-695 (1995).

[211] Higgs PG, Joany JF, J Chem Phys 94:1543-1554 (1991).

[212] Kazi IW, Rahman F, Ali SA, Polym Eng Sci DOI 10.1002/pen.23548.

[213] Davey RJ, The Role of Additives in Precipitation Processes, Industrial

Crystallization 81, Eds. Jancic SJ and de Jong EJ, North-Holland Publishing Co.,

123-135 (1982).

[214] Kazi IW, Rahman F, Ali SA, Polym Eng Sci DOI 10.1002/pen.23548

[215] Pike RM, Cohen RA, J Polym Sci 44:531-538 (1960).

[216] Martinez-tapia HS, Cabeza A, Bruque H, Pertierra P, Garcmh S, Aranda MAG, J

Solid State Chem 151:122-129 (2000).

[217] Butler GB, Angelo RJ, J Am Chem Soc 79:3128-3131 (1957).

[218] Butler GB, Acc Chem Res 15:370-378 (1982).

[219] Candau F, Joanny J-F, Salamone JC, Polyampholytes (Properties in Aqueous

Solution);. Ed.; CRC Press: Boca Raton, FL 7:5462-5476 (1996).

[220] Wittmer J, Johner A, Joanny J-F, Europhys Lett 24: 263-268 (1993).

[221] Everaers R, Johner A, Joanny J-F, Europhys Lett 37:275-280 (1997).

216

[222] Spiegler KS, Laird ADK, Principles of Desalination, Part A, 2nd edn., Academic

Press, New York (1980).

[223] David H, Hilla S, Alexander S, Ind Eng Chem Res 50:7601–7607 (2011).

[224] J. Liu, Y. Ma, T. Xu, G. Shao, J. Hazard. Mater. 178 (2010) 1021-9

[225] R. Vinodh, R. Padmavathi, D. Sangeetha, Desalination. 267 (2011) 267-276.

[226] Q. Zhang, B. Pan, W. Zhang, B. Pan, Q. Zhang, Ind. Eng. Chem. Res. 47 (2008)

3957-3962.

[227] G.P. Kumar, P.A. Kumar, S. Chakraborty, M. Ray, Sep. Purif. Technol. 57 (2007)

47-56.

[228] M. Laatikainen, K. Sirola, E. Paatero, Colloid Surface A. 296 (2007) 191-205.

[229] Y. Tao, L. Ye, J. Pan, Y. Wang, B. Tang, J. Hazard. Mater. 161 (2009) 718-22.

[230] Z.-Y. He, H.-L. Nie, C. Branford-White, L.-M. Zhu, Y.-T. Zhou, Y. Zheng,

Bioresour. Technol. 99 (2008) 7954-8.

[231] J. Liu, Y. Ma, Y. Zhang, G. Shao, J. Hazard. Mater. 173 (2010) 438-44.

[232] J. Liu, T. Xu, Y. Fu, J. Membrane Sci. 252 (2005) 165-173.

[233] P. Innocenzi, E. Miorin, G. Brusatin, A. Abbotto, L. Beverina, G.A. Pagani, et al.,

Chem. Mater. 14 (2002) 3758-3766.

[234] J. Liu, T. Xu, Y. Fu, J. Non-Cryst. Solids. 351 (2005) 3050-3059.

[235] W.-jyh Liang, C.-pang Wu, C.-yu Hsu, P.-lin Kuo, J. Polym. Sci. A: Polym. Chem.

44 (2006) 3444-3453.

[236] X. J. Zhang, T. Y. Ma, Z. Y. Yuan, J. Mater. Chem. 18 (2008) 2003-2010.

[237] K. Riedelsberger, W. Jaeger.,Des. Monomers Polym., 1 (1998) 387-407.

[238] S. A. Ali, S. Z. Ahmed, E. Z. Hamad, J. Appl. Polym. Sci. 61 (1996) 1077-1085.

[239] G.-jin Hwang, H. Ohya, J. Membrane Sci. 140 (1998) 195-203.

[240] S.A. Ali, S.Z. Ahmed, M.I.M. Wazeer, E.I. Hamad, Polymer. 38 (1997) 3385-3393.

[241] G.B. Butler, J. Polym. Sci. A: Polym. Chem. 34 (1996) 913-923.

[242] Shaikh A. Ali, N. Y. Abu-Thabit, H. A. Al-Muallem, J. Polym. Sc., Part A: Polym

chem. 48 (1996) 5693-5703.

217

[243] Ottenbrite, R. M. And Ryan, Jr. W. S., Ind. Engg. Chem. Prod. Res. Dev. 1980;

19:528-32.

[244] Chemical Economics Handbook. Menlo Park (CA): Stanford Research Institute,

1983. p. 581-10111, 581-5022L, 581-1012D.

[245] Ottenbrite RM, Shillady DD. In Polymeric Amines and Ammonium Salts; Goethals,

E. J. Ed.; Pergamon Press: Oxford, 1980; pp 143.

[246] Butler, G. B. Cyclopolymerization and cyclocopolymerization; Marcel Dekker: New

York, 1992.

[247] G.B. Butler, R.J. Angelo, J. Am. Chem. Soc. 79 (1957) 3128-3131.

[248] A. Cabeza, X. Ouyang, C.V.K. Sharma, M.A.G. Aranda, S. Bruque, A., Inorg. Chem.

41 (2002) 2325-2333.

[249] H.S. Martinez-tapia, A. Cabeza, H. Bruque, P. Pertierra, S. Garcmh, M.A.G. Aranda,

J. Solid State Chem. 151 (2000) 122-129.

[250] Martinez-tapia, H. S.; Cabeza, A.; Bruque, H.; Pertierra, P.; Garcmh, S.; Aranda, M.

A. G., J. Solid State Chem. 2000, 151, 122−129.

[251] Cabeza, A.; Ouyang, X.; Sharma, C. V. K.; Aranda, M. A. G.; Bruque, S.; Clearfield,

A., Inorg. Chem. 2002, 41, 2325−2333.

[252] Sahni, S. K.; Bennekom, R. V.; Reedijk, J. A., Polyhedron 1985, 4, 1643−1658

[253] K.H. Chong, B. Volesky, Biotechnology and Bioengineering, 47(4) (1995) 451–460.

[254] S. Veli, B. Pekey, Fresenius Environ. Bull. 13 (2004) 244–250.

[255] Logan, D. and. Walker J.L.1982. Scale Control in High Temperature MSF

Evaporators with Concurrent Acid and Inhibitor Treatment, Calgon Corporation,

Pittsburgh, Pennsylvania.

[256] Harris, A.. Desalination Technology, Ed. A. Porteous, 1983, pp. 44-48.

[257] S. Matsumura, S. Mada, S. Yoshikawa, polymer Mater. Sci. Eng., 62, 984, 1990.

[258] K. Harada, J. Org. Chem., 24, 1662, 1959.

[259] M. Tomida, T. Nakato, S. Matsunami, T. Kakuchi, Polymer, 38, 4733-4736, 1997.

[260] K. Matsubara, T. Nakato, M. Tomida, Macromolecules, 30, 2305-2312, 1997.

218

[261] T. Nakato, A. Kusono, T. Kakuchi, J. Polym. Sci.: Part A: Polym. Chem., 38, 117-

122, 2000.

[262] W. Zarges, T. Groth, W. Joentgen, A. Groschl, USP 6,187,195 B1, Feb 13, 2001

[263] H. Li, C. Liu, J. Li, Y. Xu, B. Li, Faming Zhuanli, Shenqing (2011), CN 102030421

A 20110427.

[264] C. Chen, H. Yang, S. Li, X. Liu, Y. Zhou, Wuhan Ligong Daxue Xuebao (2010),

32(18), 70-73.

[265] B. Zhang, F. Li, Y. Chen, Faming Zhuanli Shenqing (2011), CN 101962233

A 20110202.

[266] Y. Zhang, L. Xing, Z. Cao, C. Ping, S. Xu, Y. Ma, Faming Zhuanli Shenqing (2010),

CN 101928074 A 20101229.

[267] G. Jing, S. Tang, S. Li, L. Xing, L. Kong, (, Environment Materials and Environment

Management Pt. 1) (2010), 113-116, 694-697.

[268] Z. Liang, F. Hu, G. Dong, J. Li, Guangdong Huagong (2008), 35(8), 13-14, 90.

[269] Gerd B.; Wolfgang H.; Christian zum K.; Claire D.; Timo H.; Thomas G.,

Desalination, 250. 982-984, 2010.

[270] Zuback, Joseph Edward, PCT Int. Appl. (2009), WO 2009102442 A1 20090820.

[271] Ma, Yulian; Wang, Huichang; Li, Dongxia; He, Wusheng; Guo, Guihua; Guo,

Weicheng; Wang, Qiang; Zhou, Xiaochun, , Faming Zhuanli Shenqing Gongkai

Shuomingshu (2008), CN 101254413 A 20080903.

[272] Kawada, Ichiro, Jpn. Kokai Tokkyo Koho (1999), JP 11000662 A 19990106

[273] D. Hasson, H. Shemer, A. Sher Ind. Eng. Chem. Res. 2011, 50, 7601–7607

[274] Ali SA, Abu-Thabit NY, Al-Muallem HA. J Polym Sci Part A: Poly Chem

2010;48:5693–703

[275] Kandikere. R P.; Nagavarakishore P.;Hariprasad G.; Kattesh. K., J. Am. Chem. Soc.

2000, 122, 1554-1555

[276] Dan Liu, Wenbo Dong, Fengting Li, Franck Hui, Jean Lédion Desalination 304

(2012) 1–10

[277] Deive, F.J.a , Rivas, M.A.b , Rodríguez, A. J. Chem. Thermodynamics 43 (2011)

1153–1158

javascript:;

http://www.scopus.com/authid/detail.url?authorId=6507315650&eid=2-s2.0-79955600640



219

[278] P. Albertsson, Partition of Cell particles and Macromolecules, 3rd

Ed. Wiley, N.Y.

(1986)

[279] H. Walter, D. E. Brooks and D. Fischer (eds), Partitioning in Aqueous Two-Phase

systems, Academic Press, New York (1985)

[280] N. Baskir, T. A. Hatton and U. W. Sutter, Biotechnol. Bioeng.,34, 541 (1989)

[281] N. L. Abbott and T. A. Hatton, Chem. Eng. Prog. Aug. 31 (1988)

[282] N.L. Abbot, D. Blankschtein and T. A. Hatton, Bioseparation, 1, 191 (1990)

[283] P. A. Albertson and F. Tjerneld, Methods Enzymol., 228, 3 (1994)

[284] U. Dissing and B. Mattiasson, Biotechnol. Appl. Biochem., 17, 15 (1993)

[285] K. Begfeld, L. Piculell, and F. Tjerneld, Macromolecules, 28, 3360(1995)

[286] M. Svensson, P. Linse, and F. Tjerneld, Macromolecules, 28, 3597 (1995)

[287] Walter, G. Johansson, and D. E. Brooks, Anal. Biochem., 197, 1 (1991)

[288] G. Johansson, V. S. Shanbhag, J. Chromatogr., 284, 62 (1984)

[289] G. Johansson and M. Joelsson, J. Chromatogr., 392, 195 (1987)

[290] U. Sivars, K. Bergfeldt, L.Pictulell, and F. Tjerneld, J. Chromatogr., B.,680, 43

(1996)

[291] G Birkenmeier and M. Kunath, J. Chromatogr., B, 680, 97 (1996)

[292] M. Akashi, E. Yashima, T. Yamashita, N.Miyauchi, S.Sugita, and K. Maruno, J.

Polym.Sci.,Part A, Polym. Chem.Ed., 28, 3487 (1990)

[293] M. Akashi, E. Yashima, T. Yamashita, and N.Miyauchi, J. Polym. Sci., Part A,

Polym. Chem.Ed., 31, 1153 (1993)

[294] J. S. Hong, T. Nakahara, H. maeda, Y. Kikunaga, A. Kishida, and M. Akashi,

Colloid Polym. Sci., 8, 274 (1996)

[295] A. Kishida, S. Nakano, Y. Kikunaga, M. Akashi, J. Appl. Polym. Sci. 67, 255 (1998)

[296] Stefan A. Oelmeier, Florian Dismer, Ju¨ rgen Hubbuch Biotechnology and

Bioengineering, Vol. 108, No. 1, January 1, 2011

[297] Zafarani-Moattar, M.T. , Hamzehzadeh, S. Fluid Phase Equilibria Volume 304,

Issue 1-2, 15 May 2011, Pages 110-120



http://www.scopus.com/source/sourceInfo.url?sourceId=26899&origin=recordpage

220

[298] Da Silva Padilha, G. , Ferreira, J.F., Alegre, R.M., Tambourgi, E.B. Acta Scientiarum

- Technology Volume 33, Issue 1, 2011, Pages 1-4

[299] S. Naeem, G. Sadowski, Fluid Phase Equilibria. 299 (2010) 84–93

[300] S. Naeem, G. Sadowski, Fluid Phase Equilibria 306 (2011) 67– 75

[301] Ali, S. A.; Al-Hamouz, O. C. S., Polymer, (2012) 53, 3368

[302] Al-Muallem, H. A.; Wazeer, M. I. M.; Ali, S. A., Polymer, (2002) 43, 1041.

[303] Ali, S. A.; Ahmed, S. Z.; Wazeer, M. I. M.; Hamad, E. Z., Polymer, (1997) 38, 3385.

[304] Candau, F.; Joanny, F., Polyampholytes. Properties in Aqueous Solution, In

Polymeric Materials Encyclopedia, Salamone J, F. Ed. CRC Press: Boca Raton,

(1996); pp 5462.

[305] Everaers, R.; Johner, A.; Joanny, J. F., Europhys. Lett., (1997) 37, 275.

[306] Higgs, P. G.; Joanny, J. F., J. Chem. Phys., (1991) 94, 1543.

[307] Wittmer, J.; Johner, A.; Joanny, J. F., Europhys. Lett., (1993) 24, 263.

[308] Dobrynin, A. V.; Rubinstein, M.; Joanny, J.-F., Macromolecules, (1997) 30, 4332.

[309] Sukhishvili, S. A.; Granick, S., J. Chem. Phys., (1998) 109, 6861.

[310] Van, d. S. H. G. M.; Cohen, S. M. A.; De, K. A.; Bijsterbosch, B. H., Langmuir,

(1992) 8, 2538.

[311] Diamond, A. D.; Hsu, J. T., AIChE Symp. Ser., (1992) 290, 105.







221

Vitae

Name :Izzat Wajih Kazi

Nationality :Pakistani

Date of Birth :3/6/1967

Email :[email protected]

Address :KFUPM, P.O.Box: 1523, Dhahran, 31261, Saudi Arabia.

Alternative Email :[email protected]

Educational Qualifications:

PhD. Chemistry, King Fahd University of Petroleum and Minerals, 2013, (Thesis title:

Synthesis and Application of Some Ionic Polymers as Antiscalants and Components for

Aqueous Two-Phase Systems).

M.Sc. Chemistry, King Fahd University of Petroleum and Minerals, 1999 (Differential

Electrolytic Potentiometric Detector in Flow Injection Analysis).

B.Sc. Chemistry, 1990, Karachi University, Karachi, Pakistan

2013 - kfupm

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