The Islamic University – Gaza

Research and Graduate Affairs

Faculty of Science

Department of Chemistry

Template Synthesis of Iminodiacetic Acid Polysiloxane

Immobilized Ligand Systems and Their

Metal Uptake Capacity

المثبتة على أنظمة البولي حمض األسيتيكمينو ثنائي أالتحضير القالبي لمتصلة

الفلزات بعض أيونات على امتصاص سايلوكسان ودراسة قدرتها

Submitted by

Mohammad Khamees Selmi

Supervised by

Prof. Dr. Nizam M. El-Ashgar

Analytical Chemistry

Chemistry Department, Faculty of Science

The Islamic University of Gaza

A Thesis Submitted in Partial Fulfillment of Requirements for the Degree

of Master of Science in Chemistry

Chemistry Department

Gaza – Palestine

هـ 1434 – 2013م

II

III

DECLARATION

"I hereby declare that this manuscript is my own work and that, to

the best of my knowledge and belief, it contains no material

previously published, or written by another person, nor material

which to a substantial extent has been accepted for the award of

any other degree of the university or other institute, except

where due acknowledgment has been made in the text"

Signature: Moh. K. Selmi

Name: Mohammad Khamees Selmi

Date: September, 2013.

Copy Rights;

All Rights Reserved: No part of this work may be reproduced, translated or stored in

any kind of a retrieval system, without a prior permission of the author.

IV

ABSTRACT

Template Synthesis of Iminodiacetic Acid Polysiloxane

Immobilized Ligand System and Their

Metal Uptake Capacity

Two different routes for the synthesis of insoluble porous solid

functionalized ligand system bearing iminodiacetic acid chelating ligand of

the general formula P-(CH2)3N-(CH2COOH)2 (where P- represents [Si-O]n

polysiloxane network) were achieved by sol-gel template method in

presence of CTAB surfactant to formed porous materials. The first route

was achieved by the modification of 3-aminopropylpolysiloxane with

ethylchloroacetate, followed by hydrolysis with HCl to form the

polysiloxane iminodiacetic acid ligand system; P-(CH2)3N-(CH2COOH)2

(P-IDA-I). The second route was achieved by the reaction of

diethyliminodiacetate with 3-iodopropylpolysiloxane to form immobilized-

polysiloxane diethyliminodiacetate system. The diethyliminodiacetate

polysiloxane immobilized ligand system was then hydrolyzed by HCl to

form the iminodiacetic acid ligand system P-(CH2)3N-(CH2COOH)2

(P-IDA-II). Elemental analysis, 13

C NMR, XPS and FTIR results showed

that the surfactant have improved the silica network structure and increased

the metal uptake capacity of the ligand system. Thermogravimetric

analysis studies showed significant stability of the immobilized ligand

systems upon complexation with metal ions. The new functionalized ligand

systems exhibit high capacities for uptake of the metal ions

(Ni2+

, Cu2+

and Pb2+

).

Keywords: Metal Uptake, iminodiacetic Acid, diethyliminodiacetate,

surfacatants, immobilized-polysiloxane ligand systems.

V

ملخص

المثبتة على أنظمة البىلي سايلىكسان حمض األسيتيكمينى ثنائي أالتحضير القالبي لمتصلة

الفلزات بعض أيىنات على امتصاص ودراسة قذرتها

خ خحضش اماب خظت ثائ أسخاث -ح اسخخذا ساس خخف بطشمت اظ

األ واشوبت عى أظت ابى ساىوسا اظبت واسات راث اظغت

P-(CH2)3N-(CH2COOH)2 حث حث(P- شبىت ابى ساىوسا[Si-O]n) وره ف

أخ ححس اخشوب اشبى (Surfactant)راث افاعت اسطحت CTABوخىد ادة

ادة.

أىبشوب بى ساىوسا وره بخفاعها ع -3ح ححمك اساس األوي بخعذ خظت

إث وىسو أسخاث إلخاج ثائ إث أسخاث األ ث خبع ره اخح اائ دىعاث

ثىوس باسخخذا ح اهذسووىسه إلخاج اظغت احضت خظت احضشة وي اإل

P-(CH2)3N-(CH2COOH)2 , .(P-IDA-I)حائ ح أسخه األ راث اظغت:

ىدذ ابشوب بى -3أا اساس اثا فمذ ح ححممه بخفاع ثائ إث أسخاث األ ع

ساىوسا, إلحالي دىعت ثائ إث أسخاث األ زساث اىد و ث اخح اائ

ظت دىعاث اإلثىوس باسخخذا ح اهذسووىسه إلخاج اظغت احضت خ

, P-(CH2)3N-(CH2COOH)2 احضشة وي حائ ح أسخه األ راث اظغت:

.(P-IDA-II)

وأخهضة اخشخض Elemental Analysis) حب خالي خائح اخح اعظشي )

, وطاف اش اىوي اغاطس (FTIR)اطف واخ شج طاف األشعت ححج احشاء

(13

C NMR)طاف األشعت است افىحىاىخشوت , و(XPS) , بأ سشفاوخج ايCTAB لذ

ع عى ححس شبىت اسىا احات خظت ووزه صادة لذسة اخظت احضشة عى

(Thermogravimetric Analysis)اخظاص أىاث افضاث وا بج طشق اخح احشاسي

بأ يان دسخت ثباث حىظت خظت اشحبطت بظا ابى ساىوسا عذ االسحباط باىاث

افضاث اذسوست. إ اخظت ادذذة اشحبطت بظا ابى ساىوسا أظهشث لذسة عات

الخظاص اىاث فضاث اى و احاط واشطاص.

VI

DEDICATION

To my father and my mother who

taught me how to give

To my wife who supported me wholeheartedly

To my children

To my brothers and sister

To all my friends who spare no effort to help

To all of them I dedicate this work

VII

Acknowledgement

Praise be to Allah, the lord of the worlds and peace and blessings of

Allah be upon the noblest of the Prophets and Messengers, our Prophet

Mohammad.

This work has been carried out in the chemistry laboratories at the

Islamic university of Gaza, Palestine.

I wish to express my great thanks to Prof. Nizam M. El-Ashgar,

Professor of Analytical Chemistry and the former Dean of Faculty of

Science at the Islamic University of Gaza, the Supervisor of this work, for

his kind assistance, continuous and valuable advices.

I would like also to express my deepest gratitude and appreciation to

Prof. Issa M. El-Nahhal, Professor of Inorganic Chemistry at Al-Azhar

University of Gaza for supporting me during the experimental part

of my work.

I would like to thank Prof. Adel Awadalla, previous Head of the

Chemistry Department at the Islamic University of Gaza for great

assistance

and support.

I would like to express my deepest gratitude to Prof. Baker M.

Zabut, Professor of Biochemistry at the Islamic University of Gaza, he and

his coworkers that gave me a chance to study a master by inaugurate this

program in chemistry department.

I am also most grateful to all my professors in chemistry department

at the Islamic University of Gaza for the facilities they have

generously provided me.

VIII

I would like to thank all the technicians and staff of the chemistry

department in the Islamic university Gaza, especially Mr. Faraj Adwan

and Mr. Mohammed Matter for their help.

I would like also to express my thanks to all friends in the

master program for the great and lovely time that we spent together,

especially Mr. Mohammed Abu-Kmail for the nice spirit and stimulating

discussion all the time.

Finally, my thanks to everyone who helped me in my work,

that I may forgot him.

IX

TABLE OF CONTENTS

CHAPTER ONE

INTRODUCTION

Aim of this Research…………………………………………………………… 1

1.1 Definition of Heavy Metals …….....…………………….………..…………. 3

1.2 Extraction and Separation of Heavy Metals ………….…………..…………. 3

1.3 Criteria for Metal Ion Removal Method .……………….………..…………. 4

1.4 Types of Extraction Techniques. ………….….…..……..………..…………. 4

1.4.1 Solvent Extraction …………………………..………….……………….. 4

1.4.2 Polymer Filtration …………………..…..…………..………..…………. 5

1.4.3 Polymeric Ion Exchange Materials …………………..………..………... 5

1.5 Silica Based Solid Supports ……………………………..………..…………. 7

1.5.1 Silica Gel …………..………...……………...………………..…………. 7

1.5.2 Modification of Silica Gel ……………………………………………… 8

1.5.2.1 Physical Adsorption …………………………..…………………... 8

1.5.2.2 Chemical Immobilization …………...……………………..…..….. 8

1.5.3.3 Preparation of Chelating Sorbents Based on Silica Gel …………... 9

1.5.4.4 Preconcentration and Elution …………………...…………………. 9

1.6 Analytical Applications of Chelating Sorbents Based on Silica Gel ……….. 9

1.6.1 Polysiloxane Immobilized Ligand Systems …………..………..……….. 10

1.6.1.1 Definition of Polysiloxanes ………………………..……………. 10

1.6.1.2 Polysiloxanes Advantages …………...…………………………… 11

1.6.2 Preparation of Polysiloxane Immobilized Ligand System ….…………. 11

1.6.2.1 The Sol-Gel Process …………………………………..…………. 12

1.6.2.2 Steps of Sol–Gel Process ………………………………………… 12

X

1.6.2.2.1 Hydrolysis……………………………………………….. 12

1.6.2.2.2 Polycondensation………………………………………... 14

1.6.2.2.3 Gelation…………………………………………………. 16

1.6.2.2.4 Drying…………………………………………………… 16

1.6.2.2.5 Aging……………………………………………………. 16

1.7 Porous Materials……………………………………………………………... 17

1.8 Synthesis of Silica Networks Using Templates……………………………… 18

1.8.1 Template Definition……………………………………………………… 18

1.8.2 Surfactant-Templated Synthesis of Silica Networks…………………….. 18

1.8.2.1 Surfactants…………………………………………………………. 18

1.8.2.2 Types of Surfactants…………………...…………………………... 19

1.8.3 Synthesis Strategies of Mesoporous Materials………………...………… 19

1.8.4 Removal of Templates…………………………………………………… 20

1.8.5 Interactions Between Templates and Silica Precursors….………………. 21

1.8.6 Structures of Mesoporous Materials According to Surfactant Type…….. 22

XI

CHAPTER TWO

EXPERMINTAL PART

2.1 General Techniques …………………………………………..…..…………. 24

2.1.1 CP-MAS Solid State NMR Experiments ……………………....……..…. 24

2.1.2 X-ray Photoelectron Spectroscopy (XPS) ……………..……..…………. 24

2.1.3 Thermogravemetric Analysis …………….………..………………. 24

2.1.4 Elemental Analysis …………………………………......…….………… 25

2.1.5 Atomic Absorbtion Spectrophotometry ……………………..…..……... 25

2.1.6 Infrared Spectrophotometry …………………………..……..…….……. 25

2.1.7 pH Measurements ……………………………………..……..…………. 25

2.1.8 Shaking Techniques ……...………………………………..…..…..……. 25

2.2 Reagents and Materials ……………………………………….…..…………. 26

2.3 Metal Ions Solutions …………………………………..………….…………. 26

2.3.1 Standard Solutions ………………………..…………..….…..…………. 26

2.3.2 Stock Solutions ……………………………………..………..…………. 26

2.4 Buffer Solutions for pH Control……………..……………………………… 26

2.5 Preparations of Polysiloxane Iminodiacetic Acid Immobilized Ligand

System (P-IDA)……………… ………………………..……………………

27

2.5.1 Preparation of P-IDA-I from 3-Aminopropylpolysiloxane……………… 27

2.5.1.1 Preparation of 3-Aminopropylpolysiloxane Ligand System

(P-MA)…………………………………… ………………………

27

2.5.1.2 Preparation of polysiloxane Immobilized Diethyliminodiacetate

(P-DIDA-I)……………….. ……………..………………………..

27

2.5.1.3 Preparation of Polysiloxane Immobilized Iminodiacetic Acid

Ligand System (P-IDA-I)……………………………... ………….

28

XII

2.5.2 Preparation of P-IDA-II from 3-Iodopropylpolysiloxane………………. 28

2.5.2.1 Preparation of 3-Iodopropyltrimethoxysilane (L-I)……………….. 28

2.5.2.2 Preparation of Porous Polysiloxane 3-

Iodopropypolysiloxane Ligand System (P-

I)…….…..……………………………………

29

2.5.2.3 Preparation of Polysiloxane Immobilized Iminodiacetic Acid

Ligand System (P-IDA-II)….…………….……………………..

29

2.5.2.3.1 Preparation of Diethyliminodiacetate (DIDA)……………. 29

2.5.2.3.2 Immobilization Step………………………………………. 30

2.5.2.3.3 Hydrolysis Step………………………………………….. 30

2.6 Metal Uptake Experiments……………………...…………………………… 31

2.6.1 Effect of Shaking Time……………………..……………………………. 31

2.6.2 Effect of pH……………………………………………………………… 31

2.6.3 Effect of Shaking……………………………………...…………………. 32

2.6.4 Effect of Temperature …………….…………..…………….…………... 32

XIII

CHAPTER THREE

RESULTS AND DISCUSSTIONS

3.1 General Synthetic Methods of Polysiloxanes ……………..………………… 34

3.1.1 First Route: Preparation of P-IDA-I from 3-Aminopropylpolysiloxane. 35

3.1.1.1 Template Preparation of Porous Polysiloxane

3-Aminopropylpolysiloxane Ligand System (P-MA)…………..

35

3.1.1.2 Preparation of the P-DIDA-I and P-IDA-I Ligand Systems …... 36

3.1.2 Second Route: Preparation of P-IDA-II from 3-Iodopropylpolysiloxane. 37

3.1.2.1Template Preparation of Porous Polysiloxane

3- Iodopropypolysiloxane Ligand System (P-I) ………………...

37

3.1.2.2 Preparation of the P-DIDA-II and P-IDA-II Ligand Systems…… 38

3.2 FTIR Spectra ……………………………………………………..….………. 41

3.3 13C NMR Spectra ……………………………………………………………. 45

3.4 XPS Results ………………………………………………………...……... 46

3.5 Thermal Analysis………………………………………………… …………. 55

3.6 Metal Uptake Capacity ………………...……………………………………. 60

3.6.1 Effect of Surfactant Concentration……………………………………… 60

3.6.2 Effect of pH……………………………………………………………... 61

3.6.3 Effect of Temperature on Metal Uptake of P-IDA-I……………………. 62

3.6.4 Effect of Shaking………………………………………………………... 63

3.6.5 Comparison Between the Uptake of Different Metal Ions……………… 63

3.6.6 Effect of Shaking Time…………………………………………………. 64

Conclusion……………………………………………………………………….. 67

REFERENCES………………………………………………………………… 69

XIV

LIST OF SCHEMES

Scheme 1.1: Formation of polysilicic acid ……………………………………. 7

Scheme 1.2: Acid catalysis hydrolysis………………………..……………..…... 13

Scheme 1.3: Base catalysis hydrolysis………………………………..….……... 13

Scheme 1.4: Polycondensation of alkoxysilanes……………………..…………. 14

Scheme 1.5: Sol-Gel process…………………………………...…………...…... 15

Scheme 1.6: Aging process…………………………………...…………………. 16

Scheme 1.7: Cetyl Trimethyl Ammonium Bromide (CTAB)……………...…… 19

Scheme 3.1: Synthesis of polysiloxane mesoporous 3-aminopropypolysiloxane

ligand system (P-MA)……………………………………..……..

35

Scheme 3.2: Preparation of the P-DIDA-I and P-IDA-I ligand systems…….… 36

Scheme3.3:Template synthesis of polysiloxane mesoporous

3-iodopropypolysiloxane ligand system (P-I)…………………. …

37

Scheme 3.4: Preparation of the P-DIDA-II and P-IDA-II ligand systems…........ 38

XV

LIST OF FIGURES

Figure 1.1: Representative of the synthetic procedure of silica networks by

using surfactants as templates …………………………..………... 20

Figure 1.2: Interactions between inorganic species and different kinds of

surfactants in the formation of mesoporous materials…….……

22

Figure 3.1: FTIR spectra for (a) P-MA/CTAB, (b) P-MA, (c) P-DIDA-I and

(d) P-IDA-I, ligand systems (D-samples)...……….……..…..

42

Figure 3.2: FTIR spectra for (a) P-I/CTAB, (b) P-I, (c) P-DIDA-II and

(d) P-IDA-II, ligand systems (D-samples) ……..................…...

44

Figure 3.3: CP/MAS NMR 13

C spectra for (a) P-MA, (b) P-DIDA-I and

(c) P-IDA-I immobilized ligand systems of (D-samples)……….....

46

Figure 3.4: CP/MAS NMR 13

C spectra for the immobilized P-I/CTAB system

of (D-samples) ……………………………………..…………...

47

Figure 3.5: CP/MAS NMR 13

C spectra for the P-IDA-II system of (D-samples) 47

Figure 3.6: Survey regions of immobilized monoamine polysiloxane (a) (P-

MA/CTAB) in presence of CTAB and (b) after removal of CTAB.

48

Figure 3.7: Survey regions of (a) P-DIDA-I and (b) P-IDA-I…………….….. 49

Figure 3.8 (a): N1s regions from P-MA...………………………………………. 50

Figure 3.8 (b): N1s regions from P-IDA-I ……………………………………. 50

Figure 3.9: Survey regions of the (a) P-I/CTAB material and (b) P-I after

removal of CTAB ………..………………………....……...…...… 51

Figure 3.10:High resolution C1s regions from (a) P-I, (b) P-DIDA-II and

(c) P-IDA-II……………………………..……………………...… 52

Figure 3.11:High resolution N1s region for (a) P-I (b), P-DIDA-II and

(c) P-IDA-II……………….…………………………………...…. 53

Figure 3.12 (a): Thermograms of P-I prepared in absence of CTAB………..… 56

XVI

Figure 3.12 (b): Thermograms of P-I prepared in presence of CTAB …….….... 56

Figure 3.12 (c): Thermograms of P-I after CTAB was removed ………………. 57

Figure 3.13 (a): Thermograms of P-IDA-II………………….……………….… 58

Figure 3.13 (b): Thermograms of P-IDA-IIcopper (II) complex……………..… 59

Figure 3.14: Uptake of Cu (II) by P-IDA-I (D) and P-IDA-II (D) versus pH

values………………………………………………………………

61

Figure 3.15: Uptake of Cu(II) by P-IDA-I (D) versus temperatures……………. 62

Figure 3.16: Cu(II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time…….. 65

Figure 3.17: Ni(II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time…..… 65

Figure 3.18: Pb (II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time….. 66

XVII

LIST OF TABLES

Table 3.1: Immobilized polysiloxanes P-M(P-IDA-I) and P-I(P-IDA-

II) prepared at different CTAB/TEOS molar

ratios………..….…….

35

Table 3.2: Elemental analysis data for the polysiloxane-immobilized P-MA,

P-DIDA-I, P-IDA-I, P-I, P-DIDA-II, P-IDA-II(Dsamples) ……….

39

Table 3.3: XPS data and % surface composition of P-MA and its derivatives 54

Table 3.4: XPS data and % surface composition of P-I and its derivatives… 54

Table 3.5: Copper uptake by P-IDA-I and P-IDA-II at different concen-

trations of Surfactants……………..………………………..……..

60

Table 3.6: Copper uptake by P-IDA-II with and without shaking………...... 63

Table 3.7: Comparison between the uptake of different metal ions………… 64

XVIII

ABBRIVIATIONS

P-I 3-Iodopropylpolysiloxane

P-MA 3-Aminopropylpolysiloxane

P-DIDA diethyliminodiacetate polysiloxane

P-IDA polysiloxane-immobilized iminodiacetic acid

DIDA diethyliminodiacetate

CTAB Cetyl Trimethyl Ammonium Bromide

TEOS Tetraethylorthosilicate

TMOS Tetramethylorthosilicate

XPS X-ray Photoelectron Spectroscopy

TGA Thermogravemetric Analysis

FTIR Fourier Transform Infra Red

CP-MAS NMR Cross Polarization Magic Spinning Nuclear Magnetic

Resonance

SPE Solid Phase Extraction

1

Aim of this research

This work concerns with template synthesis of some of functionalized

chelating polysiloxane in presence of surfactants and to obtain porous

structure for the polymer which can be used for analytical applications such

as extraction, preconcentration and separation of some toxic heavy metals

from aqueous solutions.

2

CHAPTER ONE

INTRODUCTION

3

1.1. Definition of Heavy Metals.

Heavy metals can be defined as any metals or metalloids have density

more than 4 g/cm3, or 5 times or more greater than water [1,2], heavy

metals could enter the body system through food, air, water and bio-

accumulate over a period of time [1]. They are introduced and spread into

the environment through a number of industrial processes [3].

Some of heavy metals cause toxicity even if the concentrations are

very low and this is the main reason behind the price in the interest all over

the world [4], whereas others are biologically essential and become toxic at

relatively high concentrations, they combine with body's biomolecules, to

form stable biotoxic compounds, thus distortion their structures and

hindering them from the bioreactions of their functions [5].

Heavy metals combine with proteins and formed toxic complexes

and they can inactivate important enzyme systems [2].

1.2 Extraction and Separation of Heavy Metals.

Because of the toxicity of heavy metals there is an urgent need

for separation and preconcentration of the trace metals from different

media [6].

Direct determination using various instrumental methods is not

possible of trace metal ions present in various samples like natural and

waste water, biological and alloy samples, Because of matrix effects and

low concentration of metal ions in these samples, separation and

preconcentration of heavy metals can be occurred with various techniques

such as liquid–liquid extraction, precipitation technique, carbon adsorption,

distillation, evaporation, electrolytic concentration, capillary zone

electrophoresis, and use of chelating resins. However, the solid-phase

extraction of metal ions has gained rapid acceptance because of various

4

advantages, the extraction of metal ions using chelating resins is a very

important method since it does not involve the use of toxic chlorinated

organic solvents [7].

These techniques have been developed to remove the toxicity of

heavy metals because heavy metals are a non-degradable [3,8].

1.3 Criteria for Metal Ion Removal Methods [9].

1. A high metal ion sorption capacity.

2. Selective removal of one metal ion.

3. Operational across a range of pH values.

4. Reduction of metal ion concentrations to very low levels.

5. Mechanical and chemical integrity for an extended lifetime.

6. Economically available.

1.4. Types of Extraction Techniques.

There are several techniques were used to remove metal ions from

aqueous solutions, three of them are solvent extraction, ion exchange, and

polymer filtration [9].

1.4.1 Solvent Extraction.

In this method two immiscible liquids should be used to separate

materials according to their preference for each of them [10] .liquids used

in solvent extraction method are usually water and an organic solvent and

the extractant add to the organic solvent which used to chelate metal ions,

the complete solvent extraction can be carried out by following steps: [9]

1. Transfer of the metal ion from aqueous phase into the organic phase.

2. Removal of co-extracted materials for the purpose of increased purity.

3. Transfer of metal back into a pure aqueous phase for further processing.

4. Purification by treatment with a third aqueous phase.

5

1.4.2 Polymer Filtration.

It is an example of using water soluble chelating complexing agents

to selectively extract metal ions from aqueous solution [11]. For polymer

filtration, polymers are designed to form an ionic interaction or a

coordination complex with a target metal ion [12].

The polymer agent should be high molecular weight, chemical and

mechanical stability, low cost, low toxicity and reused. polyethyleneimine

is the most common one, it water soluble with a large degree of amine

groups which used as donor atoms in complex formation which provide a

greater degree of selectivity as a result of the specificity of complex

formation but it is toxic and cannot be used in water treatment applications,

some of acidic polymers include polyacrylic acid and polyvinyl sulfonic

acid are nontoxic and are relatively cheap. Unfortunately, they display low

selectivity for target metal ions relative to the polyamines [9].

1.4.3 Polymeric Ion Exchange Materials.

In this method ion exchanger does not dissolve and it has

heterogeneous nature of ion exchange materials which leads to flexible

and versatile metal removal processes with many advantages, at any

definitions of ion exchange materials the following points should be

taken into account [9]:

1. Insoluble materials carrying reversible fixed ions that exchanged for

other ions of the same sign.

2. A phase containing osmotically inactive insoluble carrier of

electrical charge.

3. An insoluble material that permits the exchange of ions between two or

more ionized species located in different phases.

6

There are great similarities between Ion exchange and sorption. In

both a solid extracts a dissolved species. But the difference between them is

that Sorption removes species from solution without replacement the ions.

In contrast, ion exchange must satisfy balance of charge of the solution by

exchange ions with the solution, and the functional groups immobilized on

a solid support [13].

Chelating ion exchange materials is selective method. Therefore,

depending on the functional group it can have preference for one type of

metal ion over another, and it can be readily functionalized with a wide

range of ligands [14]. For an example, Amber lite IRC-748 resin has been

functionalized with an iminodiacetic acid chelating group; these groups

allow the resins to extract large amounts of metal ion at low pH [9].

The incorporation of chelating groups onto inorganic and

hybrid solid supports finding its way into an increasing

number of applications in areas such as extraction, recovery

and separation of metal ions from aqueous solutions which

prepared by the sol–gel method [15-23]. [15,16,17,18,19,20,21,22,23].

Chelating solid phases can be made by immobilizing appropriate

chelating agents on the support matrices for selective trace-metal analysis,

silica based chelating resins are most commonly used because

immobilization reactions on silica surface relatively simple and

reproducible, especially when compared to immobilization on organic

polymers, which involve complicated multi-step reactions [7].

To remove trace metals, solid-phase extraction (SPE) has become the

most commonly method often used, the basic principle of SPE is the

transfer of analytes from the aqueous phase to the active sites of the

adjacent solid phase, naphthalene, silica and silica gel, glass beads,

cellulose, polyurethane foam, molecular imprinted polymers and other

7

supports, are types of solid phase sorbent were developed to allow more

effective extractions [24].

1.5 Silica Based Solid Supports.

1.5.1 Silica Gel.

A lot of work has been done with organic ligand grafted onto silica

surface by chemical treatment. In this process organic ligand with metal

chelating ability is directly attached or can be easily loaded on silica gel to

produce the required immobilized ligand system [25].

Synthesis of silica gel

The formation of silica gel can be obtained following two steps , the

formation of a wet gel then drying it to produce many forms of silica, wet

gel can be formed by the condensation of sodium silicate or other same

materials, silica is regarded as polymers of silicic acid consisting of

interlinked SiO4, if silicon tetrachloride is hydrolyzed Polysilicic acid will

be obtained [25,26] as shown in the( scheme 1.1)

Si Cl

Cl

Cl

Cl

n

nH2O Si OHOH

OH

OHn

Si OHOH

OH

OHn

Si OO

OH

OHn

+ 4

Silicon tetrachloride Silicic acid

Silicic acid Polysilicic acid

scheme 1.1

Alkoxysilanes have been used as precursors for silica synthesis, after

mixing of tetrachlorosilane or tetraalkoxysilane with water, silica sols will

8

be formed and by condensation small three dimensional siloxane network

are formed and the viscosity of the medium increased and at gel point the

gel will be formed [25]

advantages of silica gel

There are a lot of advantages in use of silica gel as an adsorbing

agent, it does not swell or strain, has good mechanical strength and thermal

stability, presence of silanol groups on the surface of silica gel cause low

interaction, binding and extraction of ionic species [27].

1.5.2 Modification of the silica gel

Two steps can be used to modified silica gel surface to obtain solid

sorbents with greater selectivity, physical adsorption and chemical

immobilization [28].

1.5.2.1 Physical Adsorption.

Here the organic compound will be adsorbed directly on the Si-OH

group either by passing the reagent solution through a column packed with

the adsorbent, nor by shaking the adsorbent in the reagent solution [28].

1.5.2.2 Chemical Immobilization.

In this way, a covalent bond is formed between the silica gel surface

groups and organic chelating ligand, thereby increasing the efficiency,

sensitivity and selectivity of the analytical applications than ion, simple

immobilization of the ligand on the silica surface by adsorption or

electrostatic interaction or hydrogen bond formation is the most convenient

ways to develop a silica surface [28].

9

1.5.2.3 Preparation of Chelating Sorbents Based on Silica Gel.

Two routs have been used to synthesis a lot of the polymeric

chelating sorbents:

1. The first one is the insertion of an appropriate functional group on the

surface of polymeric support and activated it.

2. The second is the immobilization of ligand with silica gel, and it is

widely used for preconcentration, separation and determination of trace

metal ions [24].

1.5.2.4 Preconcentration.

Chelating agents immobilized on silica gel support can form

complexes with metal ions only in certain pH ranges, so metal ions can

forms chelates with the chelating agent on the silica gel support and thus

are retained by the sorbent, but the impurities are not [24].

1.6 Analytical Applications of Chelating Sorbents Based on Silica Gel.

Extraction of metal ions using chelating sorbents has several

advantages over the conventional methods [24]:

1. Selective determination of metal ions by using a chelating sorbent.

2. There is no difficult phase separation, which is caused by the mutual

solubility between water and organic solvent layers.

3. It is an economical method since it uses only a small amount of ligand.

4. Trace metal ions at very low concentrations can be determined

5. Change in color intensity demonstrates the concentration of metal ions.

6. The technique is ecofriendly.

10

1.6.1 Polysiloxane Immobilized Ligand Systems.

1.6.1.1 Definition of Polysiloxanes.

Polysiloxane-immobilized ligand systems, functionalized poly-

siloxane sorbents, polyorganosiloxanes, or simply polysiloxanes are

intermediates polymers between the pure inorganic silica and organic

polymers such as polystyrene [25].

They are inorganic supports of silica based matrix bearing reactive

organic sites which have been the subject of considerable interest. These

types are known as functionalized polysiloxanes which have been prepared

either by the low temperature sol-gel process or by modification of pre-

prepared polysiloxane [29].

Flexibility of the siloxane backbone is the main reason of increasing

applications of polysiloxanes, this flexibility resulting from the degree

of Si–O–Si bond angle of 143° which is much more open than the usual

tetrahedral angle of 110°, and the Si–O bond is significantly longer than

the C–C bond [30].

Polysiloxane with chelating groups have a lot of important

applications, such as chromatography [31,32], extraction and uptake of

metal ions from aqueous solutions [33,34] and encapsulation of

organic compounds [35].

11

1.6.1.2 Polysiloxanes Advantages.

The advantages in used of polysiloxane-immobilized ligands are: [25].

1. Negligible swelling in different solutions.

2. Physical rigidity of their structures.

3. Nontoxic.

4. High biodegradation, photochemical and thermal stability.

5. High amount of functionalized groups.

6. Chemical inertness.

7. Uniform distributions of ligand sites within the polymer particles.

8. It can be modified easily by a variety of functional groups

9. High resistivity.

1.6.2 Preparation of Polysiloxane Immobilized Ligand System.

There are two common methods used to prepare these functionalize

ligand systems.

1. The first method is the sol-gel process which involves hydrolysis and

condensation of Si(OEt)4 with the appropriate silane coupling agent

(RO)3SiX where X represents an organofunctionalized ligand.

2. The second approach is the chemical modification of the pre-

prepared functionalized polysiloxane. The second method appears as

an interesting alternative mainly on account of substitution of

organofunctionalized groups when appropriate chelating silane

agents are difficult to prepare [36,37].

12

1.6.2.1 The Sol-Gel Process.

Sol gel method has attracted the attention of many researchers [38].

Sol-gel is a very flexible route for the synthesis of inorganic, organic

inorganic networks [39].

Sol-gel is a word consists of two syllables; the first is (sol) and its

mean the suspension of colloidal particles in solution, then when starting

sclerosis the gel will be formed [40] the sol-gel process can be obtained at

low temperature [39].

This process can be employed for the synthesis of functionalized

silica with controlled particle size and shape [41].

1.6.2.2 Steps of Sol–Gel Process.

1.6.2.2.1 Hydrolysis.

Alkoxysilanes are not miscible with water and many techniques used

it as gel precursors in sol gel process, a common solvent is used for

homogenization as alcohol which can provide sufficient homogenization.

Generally the hydrolysis reaction is promoted by the addition of a catalyst;

the later can be acidic or basic catalysts. Hydrolysis leads to the formation

of silanol groups instead of alkoxy silane as shown in the equation [25].

SiOR + H2O SiOH + ROH

13

Si-OR Si-OR Si-OHH3O+ +

H

H2O

++ R-OH + H+

a- Acid Catalyzed Hydrolysis:

Most of acids such as, acetic acid, phosphoric acid or sulfuric acid

have been used in this process but the most frequently used acid is

hydrochloric acid, the mechanism of hydrolysis under acidic condition is

proposed as follows (Scheme 1.2). [25].

Scheme1.2

b- Base Catalyzed Hydrolysis:

In base catalysis the reaction is caused by OH-, it is has high nucleophilic

power and is able to attack the silicon atom directly. These attacks are

aimed toward the silicon atom as the Si atom carries the highest positive

charge, the mechanism is proposed as shown in the scheme [25].

Scheme 1.3

Si-OR Si-OR Si-OHOH +

OH

+ OR

14

1.6.2.2.2 Polycondensation

The responsible for the differences between organic and inorganic

polycondensation is the hydrolytic ability of the Si-O-Si bond. Organic

polymers are formed through the formation of dimmers, trimmers, and

linear chains, which cross-link to form the gel state. Inorganic particles

however evolve either through aggregation of small colloids or by addition

of low molecular weight particles to larger ones, [25].

The polycondensation of alkoxysilanes can be formed through two

ways: silanol-silanol condensation or silanol-ester condensation [42,43].

(Scheme 1.4) .

SiOH + SiOH Si-O-Si + H2O

or

SiOR + SiOH Si-O-Si + ROH

Scheme 1.4

15

Operation of the TMOS network can be clarified through sol gel process as

shown in scheme (Scheme 1.5) [30].

1) Hydrolysis:

2) Condensation:

3) More polycondensation:

Scheme1.5

OH

OH

Si(OH)4

OH

OH

O OH

OH

OH

O

OH

O

OH

OH

O

OH

OH

O

OH

OH

O

OH

OH2SiOH O Si OH

OH

OH

SiOH SiOH

Si

SiOH

SiOSi

SiOH

SiOH+ 6 + 6

OH

OH

OH

CH3OHSi OMeMeO

OMe

OMe

OH2

OH+ 4 Si + 4

OH

OH

OH

OH

OH

OH

OH

OH

OH

OH

O OH2SiOH SiOHSi OHOH+ Si +

16

1.6.2.2.3 Gelation.

Increases interaction between particles increases viscous of the

solution and lose its fluidity and the gel is formed at gel point, when

polymerization is started, the Si-OH groups at the surface of the growing

particles are partly deprotonated and their negative charge provides a

repulsion barrier that stabilizes the sol. Latter, solvent evaporation and

water consumption by alkoxy silane hydrolysis concentrated the solution

and destabilize the suspension [30]

1.6.2.2.4 Drying.

In this stage water and other organic solvent evaporate from the

pores and the volume of the solid shrinks gradually and the final volume is

less than the initial, during this process, some of the larger pores are

emptied while smaller pores are still wet of the solvent, creating large

internal pressure gradients, this process causes cracking and fractures in

large monoliths, addition of surfactants or drying the wet gel under

monitored conditions prevents these fractures [42].

1.6.2.2.5 Aging.

In this part of sol gel process a lot of changes will be occurred on

structure and properties of the gel as a function of time, for example, new

bonds are formed, Additional cross-linking and spontaneous shrinking

occurs. The gel is aged to complete the reaction, which include further

hydrolysis and resterification. The strength of the gel increases with aging,

water and alcohol are still occurs as shown in (Scheme 1.6).

SiOR + H2O SiOH + ROH

SiOH + ROH SiOR + H2O

Scheme1.6

17

At ambient pressure and thermal evaporation xerogel is formed. But

aerogel can obtained under supercritical conditions [25].

There are several important factors controlling the structure and

properties of the sol-gel derived inorganic network such as pH,

temperature, time of reaction, reagent concentrations, catalyst constitution

and concentration, molar ratio of H2O/Si and aging temperature time [44].

1.7 Porous Materials.

Any materials containing pores called porous materials, and they

are classified to three types according to the size of the pores in

the target material, (microporous <2 nm, mesoporous 2-50 nm,

macroporous >50 nm ) [45].

M41S was the first mesoporous silica synthesized [46,47],

Preparation of porous materials taken special attention by researchers to be

used in many applications such as separation, catalysis, chemical sensing

and optical coating [48].

Mesoporos materials has possesses many characteristics such as,

highly ordered mesostructures, uniformly distributed pore size, large pore

volume and large surface area designable chemical composition and

functionalizable surface and controllable size and morphology [49].

18

1.8 Synthesis of Silica Networks Using Templates.

1.8.1 Template Definition.

Templating methods have opened the doors for researchers to design

and synthesis of ordered mesoporous materials [50], this methods described

as a central structure around which a network forms [51].

Removal of template (organic or inorganic) components can form

silica networks with porous internal environment with large specific

surface area aroused intense scientific interest for a variety of applications

including selective catalysis, drug delivery [52,53] and adsorption [54,55].

Many techniques have been used to achieve this target using natural

or synthetic inorganic or organic templates to form pores with controlled

structural features, zeolites, mesoporous molecular sieves, and silica gel are

inorganic compounds while surfactants, polymers, dendrimers, and other

colloidal particles are organic [40].

1.8.2 Surfactant-Templated Synthesis of Silica Networks.

1.8.2.1 Surfactants.

Surfactants are a shortened form of "surface-active agent" [56].

Surfactants contain both hydrophobic –tails– and hydrophilic –heads–

groups so they are amphiphilic compounds [57].

At higher concentration of surfactant more than the critical micelle

concentration (CMC) micelles can be obtained, continued increase in

concentration of surfactant in solution other forms can be found as

cylindrical micelles and then hexagonal arrays, cubic, and at very high

concentration lamellar phase can be obtained, but at very low concentration

Surfactants are present as free molecules [40].

All types of surfactants have been used as templates [58], these

template are used to form mesoporous materials [49]

19

1.8.2.2 Types of Surfactants.

There are three types of surfactants and they are classified according

to their charging properties [57].

Non-ionic surfactant (So): with neutral head groups, as ethyloxide or

propyloxide, alkyl polyesters, alkyl amines and others.

Anionic (S-) surfactant: with negatively charged head groups,

including alkyl carboxylate, phosphate, sulfate, sulphonate, etc.

Cationic (S+) surfactant: with positively charged head groups,

including alkyl quaternary ammonium salt, as Cetyl Trimethyl

Ammonium Bromide (CTAB). (C16H33)N(CH3)3Br (Scheme1.7),

CTAB is used as a cationic surfactant, it is one of the components of

antiseptic cetrimide [59] which has been used in this research.

N+

H

HH

CH2

CH2

H2C

CH2

H2C

CH2

H2C

CH2

H2C

CH2

H2C

CH2

H2C

CH2

H2C

H3C

Br-

Scheme1.7

1.8.3 Synthesis Strategies of Mesoporous Materials.

Mesoporous materials can be prepared via sol-gel technique [60]. In

sol-gel process TEOS hydrolyzed and then condensed into an oligomeric

silica sol which followed by further condensation accompanied by the self-

assembly of surfactants and inorganic species to form mesostructures, then

the surfactant can be removed, hydrolysis can be occurred in acidic or basic

medium [49]

20

Different types of surfactant can be used as templates to form

mesostructure silica networks, then the process followed by the removal of

surfactants and the materials obtained have wide pores and large specific

surface area [61].

Figure 1.1: Representative of the synthetic procedure of silica networks by using

surfactants as templates.[49]

1.8.4 Removal of Surfactant.

The surfactant can be removed via calcination, solvent reflux, or ion

exchange to leave behind a nanoporous inorganic network [62].

21

1.8.5 Interactions between Templates and Silica Precursors.

There are different type of interactions between surfactant and

inorganic species in the synthesis of mesoporous materials [49],

First type explain the formation of ionic surfactant-templated

mesostructures in different pH values. [40]:

1. S+I

- : in the basic medium, silicate anions (I

-) combine with

cationic surfactant (S+).

2. S+X

-I

+: in acidic medium, protonated silicate (I

+) combines

with cationic surfactants (S+) after the addition of inorganic

ions X-, such as Cl

-, Br

-) .

3. S-I

+: in acidic medium, protonated silicate (I

+) combines with

anionic surfactants (S-).

4. S-M

+I

-: in basic medium, the addition of metal ions M

+, leads

to the combination of silicate anions (I-) with anionic

surfactants (S-).

22

The second type occurred by using nonionic surfactant:

1. SoI

o: or the ion pair.

2. SoIX

o: under acid conditions, inorganic ions X

- such as Cl

-

and Br- are needed), can be presented due to the formation of

hydrogen bonds or dipolar interaction between surfactant and

silica species (Fig. 1.2).

Figure 1.2: Interactions between inorganic species and different kinds of surfactants

in the formation of mesoporous materials [49].

1.8.6 Structures of Mesoporous Materials According to Surfactant

Type.

The structure of mesoporous materials is highly dependent on the

geometry of surfactant, including the size and charging of headgroups,

length and saturation of hydrophobic tail and its molecular shape,

cetyltrimethylammoniumbromide (CTAB) leads to formation of

2d-hexagonal (g = 1/2) structure easily [49].

Cationic surfactants were employed as templates to prepare

hexagonal [63] cubic [64] and lamellar mesoporous silica networks. [65].

23

CHAPTER TWO

EXPERIMENTAL PART

24

2.1 General Techniques.

2.1.1 CP-MAS Solid State NMR Experiments.

13C CP-MAS Solid State NMR experiments were carried out at room

temperature on Bruker MSL-400 MHz spectrometer at frequency of 100.6

MHz (13

C ) using a bruker CP/MAS probe. Proton decoupling was always

applied during acquisition. Solid samples were spun at 5 kHz using 7 mm

ZrO2 rotors filled in a glove-box under dried argon atmosphere.

2.1.2 X-ray Photoelectron Spectroscopy (XPS).

The X-ray photoelectric spectra (XPS) were recorded on an

ESCALAB 250, spectrometer equipped with a monochromatic AlK X-ray

source (hѵ = 1486.6 eV, 650 m spot size). An electron flood gun was used

to obtain a perfectly uniform static charge over the sample area analyzed.

The filament current was 3A and the emission current 0.2 mA. These

conditions yield negative but uniform static charge over the powder

surface. Binding energy positions were calibrated against the main

C-C/C-H C1s component set at 285 eV. The surface elemental composition

was determined by considering the peak areas and the corresponding

Scofield sensitivity factors corrected for the electron analyzer

transformation function.

2.1.3 Thermogravemetric Analysis.

Thermogravemetric analysis TGA was carried out using Mettler

Toledo SW 7.01 analyzer in the range of 25-600 oC under nitrogen.

25

2.1.4 Elemental Analysis.

Analysis for carbon, hydrogen, and nitrogen were carried out, using

an Elemental Analyzer EA 1110-CHNS CE Instrument.

2.1.5 Atomic Absorbtion Spectrophotometry.

The concentrations of metal ions in their aqueous solutions were

measured using a Perkin-Elmer AAnalyst-100, spectrometer.

2.1.6 Infrared Spectrophotometry.

The infrared spectra for the materials were recorded on a Perkin-

Elmer FTIR, spectrometer using KBr disk in the range 4000 to 400 cm1

.

2.1.7 pH Measurements.

All pH measurements were obtained using AD1020 pH Meter.

2.1.8 Shaking Techniques.

All ligand samples were shaken with aqueous metal ion solutions

using an ELEIA-Multi Shaker.

26

2.2 Reagents and Materials.

Tetraethylorthosilicate, 3-chloropropyltrimethoxysilane,

3aminopropy-trimethoxysilane, iminodiacetic acid and ethylchloroacetate

were purchased from (MERCK) and used as received. Acetone, diethyl

ether, tetrahydrofurane (THF) and ethanol (spectroscopic grade) were used

as received. Cetyltrimethylammoniumbromide (CTAB) surfactant was

purchased from MERCK and used as received. Surfactant solutions of

different concentrations were prepared in ethanol. Metal ions solutions

of the appropriate concentration were prepared by dissolving the

metal chloride or nitrate (analar grade) in distilled water. Different pH

values in the range (3.5 – 6) were controlled using acetic acid/sodium

acetate buffer solution.

2.3 Metal Ions Solutions.

2.3.1 Standard Solutions.

All standard solutions of metal ions were prepared from their chloride

or nitrate salts in analar grade by dissolving a known amount of the salt in

distilled water to the appropriate range of ion concentration (ppm).

2.3.2 Stock Solutions.

Metal ion solutions (Ni2+

, Cu2+

and Pb2+

) of appropriate concentrations,

were prepared by dissolving the metal chloride or nitrate in distilled water.

2.4 Buffer Solutions for pH Control.

Different pH values (3.5 – 6) were controlled using acetic acid / sodium

acetate buffer.

27

2.5 Preparations of Polysiloxane Iminodiacetic Acid Immobilized

Ligand System (P-IDA).

The target polymer was prepared by two routes as following.

2.5.1 Preparation of P-IDA-I from 3-Aminopropylpolysiloxane.

2.5.1.1 Preparation of 3-Aminopropylpolysiloxane Ligand System

(P-MA) [30].

Porous polysiloxane 3-aminopropylpolysiloxane ligand system (P-

MA) was prepared by adding 3-aminopropyltrimethoxysilane

(8.96 g, 0.05 mol) to a stirred solution of tetraethylorthosilicate

(20.83 g, 0.1 mol) in 15 cm3 ethanol in presence of CTAB. Different molar

ratios of CTAB/TEOS; 0:1(A), 1:32(B), 1:16(C) and 1:8(D) were used

(Table 1). 4.95 cm3 of 0.42 M HCl was added as a catalyst. The mixture

was stirred at room temperature and gelation occurred within few minutes.

The product was left to stand for 12 hours, and then dried in the oven at

90 oC. The solid material was crushed washed with water, ethanol and

diethyl ether and then dried at 100oC for six hours. CTAB was extracted

from the material using hot ethanol. The material was washed successively

with 50 cm3 portions of 0.025 M NaOH, water, ethanol and diethyl ether.

The product was then dried in oven at 100 oC for 12 hours.

2.5.1.2 Preparation of polysiloxane Immobilized Diethyliminodiace-

tate (P-DIDA-I) [30].

Diethyliminodiacetate polysiloxane was prepared by the reaction of

P-MA (5 g) with an excess of ethylchloroacetate (12.2 g, 0.1mol) in 50 cm3

of THF and 1.5 cm3 of triethyamine was added to react with the liberated

chloride. The mixture was stirred and refluxed at 95 oC for 48h. The

product was filtered off, washed with 0.025 M NaOH, water, ethanol and

diethyl ether, then dried at 100 oC for 12 hours.

28

2.5.1.3 Preparation of Polysiloxane Immobilized Iminodiacetic Acid

Ligand System (P-IDA-I) [30].

The immobilized diethyliminodiacetate polysiloxane, P-DIDA-I

(5.0 g) was hydrolyzed by refluxing the ligand system with 150 cm3 of 2.0

M HCl for 12 hours with stirring. The solid material was then filtered,

washed with 0.025 M NaOH aqueous solution, water, ethanol and diethyl

ether. The material was dried at 100 oC for 12 hours and polysiloxane

immobilized iminodiacetic acid ligand system (P-IDA-I) was obtained.

2.5.2 Preparation of P-IDA-II from 3-Iodopropylpolysiloxane.

2.5.2.1 Preparation of 3-Iodopropyltrimethoxysilane (L-I).

The 3-iodopropyltrimethoxysilane was prepared [42,66], by adding

3-chloropropyltrimethoxysilane (19.87 g, 0.10 mole) dropwise with stirring

to a solution of sodium iodide (15 g, 0.10 mole) in 100 cm3 of dry acetone,

at room temperature. The mixture was refluxed at 70 oC for 48 hours.

White solid of NaCl was filtered off and the solvent was removed under

reduced pressure (40 cm Hg), at 60 oC. The residue was extracted four

times using 100 cm3 of diethyl ether using a separatory funnel. The diethyl

ether was removed by distillation at 35 oC, producing a light

yellow oily product.

29

2.5.2.2 Preparation of Porous Polysiloxane 3-Iodopropypoly-siloxane

Ligand System (P-I).

3-Iodopropylpolysiloxane was prepared [42]

by adding

3-iodopropyltrimethoxysilane (14.5 g, 0.05 mol) to stirred solution of

tetraethylorthosilicate (20.8 g, 0.1 mol) in 20 cm3 ethanol, followed by 4.95

cm3 of 0.42 M HCl as a catalyst. In this stage different amounts of CTAB

surfactant dissolved in ethanol were added in separate experiments.

Different molar ratios of CTAB/TEOS; 0:1(A), 1:32(B), 1:16(C) and

1:8(D) were used (Table 1). The mixture was stirred at room temperature

for several hours. Gelation occurred after 24 hours; the gel was left for

12 hours then dried at 100 oC overnight. The material was crushed, sieved,

washed with successive portions, of 50 cm3 of water, ethanol and diethyl

ether. CTAB was extracted from the material using hot ethanol. The

material then was washed successively with 50 cm3 portions of 0.025 M

NaOH, water, ethanol and diethyl ether. Finally the product was dried for

12 hours at 100 oC.

2.5.2.3 Preparation of Polysiloxane Immobilized Iminodiacetic Acid

Ligand System (P-IDA-II).

The polysiloxane-immobilized iminodiacetic acid ligand system

(P-IDA-II) was prepared using three steps reaction as follow:

2.5.2.3.1 Preparation of Diethyliminodiacetate (DIDA).

The diethyliminodiacetate (DIDA) was prepared as described

previously [42] by adding iminodiacetic acid (30.0 g 0.4 mol ) to 300 cm3

of absolute ethanol with stirring , and thionyl chloride (93.86 g, 0.8 mol)

was added dropwise. The reaction mixture was stirred and refluxed at 80 oC

until all the iminodiacetic acid was dissolved. The reaction was allowed to

30

proceed under reflux for 5 hours, then cooled to room temperature and the

excess of ethanol and SO2 was removed by evaporation. The residue was

dissolved in 100 cm3 distilled water and 150 cm

3 of chloroform was added.

Then 33% of sodium hydroxide solution was added dropwise with shaking

after each addition, so that the diethyliminodiacetate passed into the

chloroform and pH of the solution was adjusted to around 7. The aqueous

layer was extracted repeatedly with chloroform (4 × 150 cm3). The layer of

chloroform was separated and then dried for 2 hours over anhydrous

MgSO4 the chloroform was removed by distillation

2.5.2.3.2 Immobilization Step.

Diethyliminodiacetate polysiloxane was prepared by adding

diethyliminodiacetate (9.45 g 0.05 mol) to 10 g of 3-iodopolysiloxane in 50

cm3 of THF. The mixture was stirred and refluxed at 95

oC. The product

was filtered off, washed with 0.025 M NaOH, water, ethanol and diethyl

ether, then dried at 100 oC for 12 hours.

2.5.2.3.3 Hydrolysis Step.

Polysiloxane immobilized diethyliminodiacetate (5.0 g) was

hydrolyzed by refluxing the ligand system with 150 cm3 of 2.0 M HCl for

12 hours with stirring. The solid material was then filtered, washed with

0.025 M NaOH aqueous solution, water, ethanol and diethyl ether. The

material was dried at 100 oC for 12 hours.

31

2.6 Metal Uptake Experiments.

A 100 mg of the functionalized polysiloxane-immobilized ligand

system, (P-IDA-I or P-IDA-II) was shaken with 25 cm3, of 0.025 M of

aqueous solution of the appropriate metal ions (Ni2+

, Cu2+

and Pb2+

) using

100 cm3 polyethylene bottles. Determination of the metal ion concentration

was carried out by allowing the insoluble complex to settle down and

appropriate volume of the supernatant was withdrawn using a micropipette

then diluted to the linear range of the calibration curve for each metal. The

metal ion uptake was calculated as mmol of M2+

/g ligand. Each study was

performed at least in a triplicate. Metal uptake was examined under various

factors including the amount of surfactant, pH, shaking time, temperature

and shaking effect.

2.6.1 Effect of Shaking Time.

A 100 mg of each ligand system was shaken with metal ions aqueous

solution (25 cm3, 0.025M) at pH 6 and 70

oC. The samples were shaken at

different time intervals. The concentration of each solution was analyzed

by atomic absorption spectrometry. The metal uptake capacity of the ligand

was calculated as mmol of metal ions per one gram of the ligand system as

a function of time.

2.6.2 Effect of pH.

A 100 mg of each ligand system was shaken with metal ions aqueous

solution (25 cm3 0.025M) at different pH values. The pH was

controlled in the range 3.5 – 6 using acetic acid/sodium acetate buffer

solution. The concentration of each solution was analyzed by atomic

absorption spectrometry.

32

2.6.3 Effect of Shaking.

Studying the effect of shaking on the capacity of metal uptake by the

functionalized polysiloxane system was carried out by mixing 100 mg of

ligand system with M2+

aqueous solution (25 cm3 0.025M ) at pH 6, 70

oC

for 72 hours using acetate buffer. The metal uptake was measured with

shaking and without shaking in separate experiments.

2.6.4 Effect of Temperature.

A 100 mg of each ligand system was shaken with metal ions aqueous

solution (25 cm3 0.025M) at pH 6 for 72 hours in different temperature

(25-70) o

C using acetic acid/sodium acetate buffer solution. The

concentration of each solution was analyzed by atomic

absorption spectrometry.

33

CHAPTER THREE

RESULTS AND

DISCUSSION

34

3.1 General Synthetic Methods of Polysiloxanes.

The porous functionalized polysiloxane immobilized iminodiaacetic

acid ligand systems, P-IDA, was prepared in two different routes based on

sol-gel process.

The first route was achieved by the following steps [36]:

i. Preparation of porous 3-aminopropylpolysiloxane functionalized

system (P-MA) in presence of CTAB surfactant by the sol-gel

process.

ii. Preparation of polysiloxane-immobilized diethyliminodiacetate

(P-DIDA) by the reaction of ethylcholoroacetate with

3-aminoropylpolysiloxane P-MA in presence of THF.

iii. Hydrolysis of P-DIDA by HCl to form polysiloxane-immobilized

iminodiacetic acid (P-IDA-I).

The second route was achieved by the following steps [48]:

i. Preparation of porous 3-iododopropylpolysiloxane functionalized

system (P-I) in presence of CTAB surfactant by the sol-gel process.

ii. Preparation of polysiloxane-immobilized diethyliminodiacetate

(P-DIDA) by the reaction of diethyliminodiacetate with

3-iodopropylpolysiloxane in THF.

iii. Hydrolysis of P-DIDA by HCl to form polysiloxane-immobilized

iminodiacetic acid (P-IDA-II).

35

Table 3.1: Immobilized polysiloxanes P-M (P-IDA-I) and P-I (P-IDA-II) prepared at

different CTAB/TEOS molar ratios.

CTAB/ TEOS

molar ratios P-M(P-IDA-I) P-I(P-IDA-I)

0:1 A A

1:32 B B

1: 16 C C

1:8 D D

3.1.1 First Route: Preparation of P-IDA-I from

3-Aminopropylpolysiloxane.

3.1.1.1 Template Preparation of Porous Polysiloxane

3-Aminopropylpolysiloxane Ligand System (P-MA).

The functionalized porous polysiloxane immobilized

3-aminopropyl immobilized ligand system, P-MA, was prepared in one

step reaction based on a direct sol-gel process by

hydrolytic polycondensation of 3-aminopropyltrimethoxy silane with

tetraethylorthosilicate, of 1:2 molar ratio respectively in the presence

of CTAB as surfactant (Schemes 3.1). Different molar ratios

of CTAB/TEOS 0:1(A), 1:32(B), 1:16(C) and 1:8(D) were used

(Table 3.1). The elemental analysis results of P-MA (D) are given

in Table 3.2.

Scheme 3.1

(CH3O)

3Si(CH

2)

3-NH

2

H2O/Ethanol

O

O

O

SiCH2-CH

2-CH

2-NH

2TEOS

CTAB

+

36

O

O

O

Si-CH2-CH

2-CH

2-NH

2

N(Et)3

O

O

O

Si-CH2-CH

2-CH

2

CH2

CH2

C

O

O

O

Si

CH2

CH2

C

-CH2-CH

2-CH

2

ClCH2COOC

2H

5 THF/reflux

CH2CH

3

CH2CH

3

+

C

O

O

O

O

N

HCl

P-MA ethylchloroacetate

P-DIDA-I

P-IDA-I

C

O

O

N

OH

OH

3.1.1.2 Preparation of the P-DIDA-I and P-IDA-I ligand systems.

The immobilized iminodiacetate ligand system was prepared

by chemical modification of the preformed 3-aminopropylpolysiloxane

(P-MA) with the ethylchloroacetate in the presence of triethyl amine

(Scheme 3.2).

The immobilized diethyliminodiacetate was then hydrolyzed by

hydrochloric acid to produce the carboxylic acid form (Scheme 3.2).

Scheme 3.2

37

3.1.2 Second Route: Preparation of P-IDA-II from

3-Iodopropylpolysiloxane.

3.1.2.1 Template Preparation of Porous Polysiloxane 3-Iodopro-

pypolysiloxane Ligand System (P-I).

The 3-iodopropylpolysiloxane was prepared as reported before [48],

in which 3-iodopropyltrimethoxysilane (L-I) was first obtained from the

reaction of 3-chloropropyltrimethoxysilane with an excess of sodium

iodide using acetone as a solvent under reflux (Scheme 3.3). The

3-iodopropylpolysiloxane (P-I) was then obtained by hydrolytic

condensation of 3-iodopropyltrimethoxysilane and TEOS in the ratio of 1:2

(Scheme 3.3). Different ratios of CTAB surfactant with respect of TEOS

were added during the hydrolytic process in order to improve the

macrostructure of the polysiloxane matrix. Different molar ratios of

CTAB/TEOS 0:1(A), 1:32(B), 1:16(C) and 1:8(D) were used (Table 3.1).

NaIacetone

(CH3O)

3Si(CH

2)3I + NaCl(CH

3O)

3Si(CH

2)

3Cl

48 hr, 70oC

+reflux

(CH3O)

3Si(CH

2)

3I

O

O

O

Si(CH2)

3ISi(OC

2H

5)

4

H2O/MeOH

+ 2HCl/CTAB

P-I

Scheme 3.3

The elemental analysis results of the product P-I are given in Table 3.2.

38

O

O

O

SiCH2CH

2CH

2-I

CH2

CH2

C

C2H

5

C2H

5

O

O

O

Si-CH2-CH

2-CH

2

CH2

CH2

C

O

O

O

Si

CH2

CH2

C

-CH2-CH

2-CH

2

CH2CH

3

CH2CH

3

N(Et)3

THF/reflux+

C

O

O

O

O

HN

P-I DIDA

C

O

O

O

O

N

HCl

P-DIDA-II

P-IDA-II

C

O

O

N

OH

OH

3.1.2.2 Preparation of the P-DIDA-II and P-IDA-II Ligand Systems.

The immobilized iminodiacetate ligand system was prepared [48] by

chemical modification of the preformed 3-iodopropylpolysiloxane (P-I)

with the diethyliminodiacetate (DIDA) in the presence of triethyl

amine (Scheme 3.4).

The immobilized diethyliminodiacetate was then hydrolyzed by

hydrochloric acid to produce the carboxylic acid form (Scheme 3.4).

Scheme 3.4

39

Table 3.2: Elemental analysis data for the polysiloxane-immobilized P-MA,

P-DIDA-I, P-IDA-I, P-I, P-DIDA-II, P-IDA-II(D samples)

polysiloxane

elemental

C%

H%

N%

I%

C/N

C/I

mmol

N/g

mmol

I/g

P-MA Expected 15.65 3.47 6.08 - 3.00 - 4.34 -

found 17.48 3.67 3.61 - 5.60 - 2.57 -

P-DIDA-I

Expected 32.83 4.97 3.48 - 11.00 - 2.48 -

found 21.46 4.28 2.32 - 10.79 - 1.66 -

P-IDA-I Expected 24.27 3.46 4.04 - 7.01 - 2.88 -

found 11.48 3.43 2.13 - 6.28 - 1.52 -

P-I Expected 10.55 1.76 - 37.2 - 3.00 - 2.92

found 9.3 2.26 - 32.3 - 3.04 - 2.54

P-DIDA-II Expected 32.83 4.97 3.48 - 11.00 - 2.48 -

found 21.46 4.28 2.32 - 10.79 - 1.66 -

P-IDA-II Expected 24.27 3.46 4.04 - 7.01 - 2.88 -

found 16.84 3.66 2.29 - 8.57 - 1.63 -

For P-MA and P-I result shown in the table 3.2 it is found that

percentage of C is higher than the expected value in P- MA which is due to

presence of CTAB residue and not all CTAB material extractedcompletely.

But fo P-I it is obvious that the elemental analysis for carbon and iodine are

lower than the expected one. This can be explained by the formation of

small oligomers of low molecular weights as a result of self-condensation

of 3-iodopropyltrimethoxysilane, which were washed away. Self-

condensation of monomers can be enhanced by the different rates of

hydrolysis of the silane agents that are bearing different alkoxy groups

[67].On the other hand the higher percentage of H compared with that of

expected value in each, may be explained due to the presence of

uncondensed hydroxyl groups. This explanation has been confirmed with

29Si NMR results [68,69].

40

For P-MA, The N percentage is lower than expected due to

formation of small oligomers which leached during the washing process in

addition to presence of CTAB residues which increase the molecular

weight of the ligand system. Formation of these small oligomers is

enhanced by the presence of self-base catalyzed amino groups which lead

to rapid gelation, so small amounts of non-cross linked

oligomers are formed [70,71].

It is clear from Table 3.2 that there is lower C and N percentages of

P-DIDA-I and P-DIDA-II than those expected which is probably due to

incomplete reaction of the amino group of P-MA with ethylchloroacetate

when P-DIDA-I was formed and to incomplete substitution reaction of the

iodine present in the polymeric matrix when P-DIDA-II was formed . This

incomplete reaction probably due to steric hindrance of the large DIDA

molecules. Another reason is that only the surface amino or iodo groups

reacted with diethyliminodiacetate ligand and which may block other sites

within the pores or some amino groups are burred into the bulk and are not

accessible for replacement reaction. This explanation has been supported

by electron microscopic studies of previously reported results [48].

Evidences were confirmed by the solid state 13

C NMR and XPS results

discussed latter.

The elemental analysis of P-IDA-I shows that there is a decrease of

carbon percentages due to the hydrolysis of ethoxy groups into the acid

form. This was confirmed by the XPS results discussed later.

41

3.2 FTIR Spectra.

FTIR spectra were obtained for P-MA/CTAB , P-MA, P-DIDA-I and

P-IDA-I, ligand systems (D-samples) and given in (Fig. 3.1) The spectra

show three region of absorption at 3500 – 3000 cm-1

due to ѵ(OH ) or

ѵ(N-H) , 1750 – 1500 cm-1

due to (OH ) or (NH), ѵ(C=O ) or ѵ(CO-N)

and 1200 – 900 cm-1

due to ѵ( Si-O ) vibration. (Fig.3.1(a)) and

(Fig. 3.1(b)) show the spectra of P-MA/CTAB and P-MA where the two

absorptions at 2920 and 1474 cm-1

disappear upon removal of CTAB. The

FTIR spectrum for the immobilized polysiloxane P-DIDA-I (Fig. 3.1(c))

shows the strong absorption at 1740 cm-1

due to ѵ(C=O) vibration of the

ester form (-COOEt). Whereas the spectrum of the immobilized P-IDA-I

(acid form) ligand system ( Fig. 3.1(d)) shows a strong absorption at 1670

cm-1

due to ѵ( C=O ) vibration .

42

Figure 3.1: FTIR spectra for (a)P-MA/CTAB , (b) P-MA, (c) P-DIDA-I and (d) P-IDA-I,

ligand systems (D-samples).

43

FTIR spectra were obtained also for P-I/CTAB , P-I, P-DIDA-II and

P-IDA-II, ligand systems (D-samples) and given in (Fig. 3.2) The spectra

show three region of absorption at 3500 – 3000 cm-1

due to ѵ(OH ) or ѵ(N-

H) , 1750 – 1500 cm-1

due to (OH ) or (NH), ѵ(C=O ) or ѵ(CO-N) and

1200 – 900 cm-1

due to ѵ( Si-O ) vibration. (Fig.3.1(a)) and

(Fig. 3.1(b)) show the spectra of P-I/CTAB and P-I where the two

absorptions at 2920 and 1474 cm-1

disappear upon removal of CTAB. The

FTIR spectrum for the immobilized polysiloxane P-DIDA-II (Fig. 3.1(c))

shows the strong absorption at 1740 cm-1

due to ѵ(C=O) vibration of the

ester form (-COOEt). Whereas the spectrum of the immobilized P-IDA-II

(acid form) ligand system ( Fig. 3.1(d)) shows a strong absorption at 1670

cm-1

due to ѵ( C=O ) vibration .

44

Figure 3.2: FTIR spectra for (a)P-I/CTAB , (b) P-I, (c) P-DIDA-II and (d) P-IDA-II,

ligand systems (D-samples).

45

3.3 13C NMR Spectra.

The CP/MAS NMR 13

C spectra for P-MA, P-DIDA-I and P-IDA-I

immobilized ligands system of (D) samples are given in ( Fig. 3.3). The

spectrum for the immobilized P-MA in (Fig. 3.3 (a)) shows three signals at

10.5, 21.5 and 45.0 ppm correspond to three methelylene carbon atoms

Si-CH2-, -CH2- and CH2-N, receptively. The CP/MAS 13

C NMR spectrum

of the immobilized diethyliminodiacetate ligand system (P-DIDA-I) is

given in (Fig. 3.3 (b)). The spectrum shows three signals at 10.1, 23.5 and

44.5 ppm due to the three methylene carbons -CH2-, -CH2- and CH2-N

respectively. The broad signal at 168 ppm is due to the carbonyl -C=O. The

two shoulders at 18 and 53 ppm are assigned due to –CH3 and -OCH2 of

acetate group. The signal around 60 ppm is assigned due to methylene

carbon of NCH2-COOEt group. These assignments were made based on

spectral data of previously reported similar systems [2].

The CP/MAS 13

C NMR spectrum for the immobilized iminodiacetic

acid ligand system P-IDA-I, is shown in (Fig. 3.3 (c)). The spectrum shows

three carbon signals at 10.1, 23.3, 42.7 ppm due to three methylene carbons

Si-CH2-,-CH2- and CH2-N respectively. The signal at 50 ppm is due to

unhydrolyzed –OEt. The presence of two signals at 18.0 and 53.5 ppm are

corresponds to CH3 and –OCH2 which provide evidence for the presence of

some unhydrolyzed (-OCH2CH3) groups even after treating with HCl[42].

Further evidence was confirmed by FTIR. The signals at 170 ppm is

due to the carbonyl –C=O group and the signal at 60(sh) ppm is due to

methylene carbon of NCH2-COOH group.

46

Figure 3.3: CP/MAS NMR 13

C spectra for (a) P-MA, (b) P-DIDA-I and

(c) P-IDA-I immobilized ligand systems of (D- samples).

The CP/MAS 13

C NMR spectra for the immobilized P-I/CTAB and its

P-IDA-II derivative of (D) samples are given in (Fig. 3.4) and (Fig 3.5)

respectively.

The spectrum of P-I/CTAB given in ( Fig. 3.4) shows three signals

at ~10 (sh), 15.2 and 25.5 ppm due to three methylene carbons

Si-CH2-, -CH2- and CH2-N respectively[42]. Signals at 27 , 30 , 33 and 34

are probably due to CTAB. Signals at 55 and 54 ppm are due to N+(CH3)3 .

Signals at ~18 and 63 ppm are probably due to unhydrolyzed

alkoxy groups.

The spectrum of P-IDA-II derived from the reaction between P-I and

diethyleneiminodiaceticatate groups given in (Fig. 3.5) shows peaks at 7.9,

15.10 and 53.7 ppm corresponds to three methylene carbons -CH2-, -CH2-

and CH2-N respectively[42]. The presence of peak at 26.01 ppm is

probably due to -CH2-I which provide evidence that the reaction between

(CH2-I) group and H(NCH2COOEt) is not completed. Further evidence was

47

confirmed by XPS results. The signals at 18 and 63 ppm are due to

unhydrolyzed –OEt groups.

Figure 3.4: CP/MAS NMR 13

C spectra for the immobilized P-I/CTAB system of

(D- samples).

Figure 3.5: CP/MAS NMR 13

C spectra for the of P-IDA-II system of (D- samples).

48

3.4 XPS Results.

Figure 3.6 displays the survey regions of immobilized monoamine

polysiloxane (P-MA/CTAB) in presence of CTAB ( Fig. 3.6 (a)) and after

removal of CTAB ( Fig. 3.6 (b)). The main peaks for Si2p, C1s, N1s, O1s

are centered at 102, 285, 400, 533 eV respectively. Evidence for the

presence of CTAB is due to the presence of high carbon content and

bromine detection. Removal of CTAB from P-MA was evident and visible

from the law content of carbon (Table 3.3) and absence of bromine peaks at

68 and 187 eV ( Fig. 3.6 (b)). Removal of the cationic surfactant CTAB

from P-MA results in a much less intense C1s peak (Fig. 3.6 (b)) and a

depression of carbon content at surface from 53.9 to 27.8 %, that is almost

twice less (Table 3.3), that is also clear from the atomic ratio of Si/C which

increases from 0.3 for P-MA/CTAB to 0.9 for P-MA without CTAB.

Figure 3.6: survey regions of immobilized monoamine polysiloxane (a) (P-MA/CTAB)

in presence of CTAB and (b)P-MA after removal of CTAB.

49

When acetate groups were introduced onto silica network by the

reaction between the immobilized P-MA ligand system and ClCH2COOEt

to obtain P-DIDA-I ester form, there was an increase of carbon content

(Table 3.3), that is also evident from the C1s region, which exhibits three

components contered at 285 , 286.5 and 289.1 eV assigned to C-C/C-H,

C-O and O-C=O respectively (Fig 3.7(a)). After the hydrolysis of

P-DIDA-I ester form by HCl to form P-IDA-I acid form , there was a

reduction of carbon content, which is clearly seen from the C1s region

(Fig 3.7(b)) (Table 3.3). The peak area of the C1s component at ~286.3 due

to C-O bonds is reduced after hydrolysis. And the ester group the

–COO-CH2CH3 is transformed in –COOH therefore eliminating the carbon

atom in the O-C group (–COO-CH2CH3), hence attenuation of the extent of

C-O carbon atom types.

(a) (b)

Figure 3.7 : Survey regions of (a) P-DIDA-I and (b) P-IDA-I.

50

Figure 3.8 a&b displays N1s regions from P-MA and P-IDA-I. The

high binding energy component centred at 402 eV is due to quaternary

ammonium, whereas the low binding energy N1s component at ~399.5 eV

is assigned to free amine from the gel. The removal of CTAB from P-MA

does not give a decrease of N+/N ratio (see Table 3.3), but the Si/N

atomic ratios increases from 3.24 for P-MA/CTAB to 4.29 for P-MA after

CTAB is removed, which is evident that less N content is pronounced.

Figure 3.8 (a) N1s regions from P-MA.

Figure 3.8 (b) : N1s regions from P-IDA-I

51

0 200 400 600 800 1000

0

50k

100k

150k

200k

I3d

N1s

O1s

C1s

Si2p

(b)

(a)

I (c

ps)

Binding energy (eV)

Figure 3.9 display the survey regions of the P-I/CTAB material

(Fig. 3.9(a)) and after removal of CTAB to form P-I (Fig. 3.9(b)). The main

peaks Si2p, C1s, N1s, O1s and I3d are centered at ~ 102, 285, 400, 532 and

619-630 eV, respectively (Fig. 3.9(a)). Efficient removal of CTAB from

P-I/CTAB is readily visible by the massive attenuation of I3d relative

intensity and absence of N1s region in P-I survey spectrum (Fig. 3.9(b)).

The surface compositions were determined; they are given in (Table 3.4).

Figure 3.9 : Survey regions of the (a) P-I/CTAB material and (b) P-I after removal of

CTAB.

Synthesis of P-I in presence of CTAB imparts a material with

highest content of carbon (57.4%). Removal of CTAB yields a quantitative

decrease of carbon from 57.4 to 32%. Esterification of P-I by DIDA which

yield P-DIDA-II, gives an increase of C/Si ratio from 1.2 to 1.9. Although

hydrolysis is expected to remove ethyl groups from ligand and therefore

a decrease in C/Si ratio, it is observe a slight increase of this ratio to 2.2,

nevertheless still higher than 1.2 determined for P-I.

52

280 285 290 295

0

10k

20k

30k

COOC2H

5

COOH

C-C/C-H

C-O

(c)

(b)

(a)

I (c

ps)

Binding energy (eV)

The high resolution C1s regions from P-I, P-DIDA-II, P-IDA-II are

displayed in (Fig. 3.10) P-I has a simple structure (Fig. 3.10 (a)) that is

very well distinguished from that of P-DIDA-II (Fig. 3.10 (b)) as a result

of reaction of P-I with diethyliminodiacetate. The C1s region form P-DIDA

exhibits indeed three components centered at 285, 286.5 and 289.1eV

(in the 1:0.52:0.07 ratio) assigned to C-C/C-H, C-O and O-C=O,

respectively (Fig. 3.10 (b)). Upon hydrolysis of P-DIDA-II, the sol gel

material P-IDA-II was obtained. Effective hydrolysis gave three similar

components centered at 285, 286.4 and 288.8 eV (in the 1:0.35:0.05 ratio),

however with significantly lower relative intensity for the C-O bond

component centered at 286.4 eV (Fig. 3.10 (c)). Indeed the transformation

of –N(COO-CH2CH3)2 into –N(COOH)2 induces the loss of the alkoxy

O-CH2CH3 and thus the attenuation of C1s component due to O-CH2 band.

Figure 3.10 : High resolution C1s regions from (a) P-I, (b) P-DIDA-II and

(c) P-IDA-II.

53

The high resolution N1s region is displayed for P-I, P-DIDA-II,

P-IDA-II (Fig.3. 11). There is no nitrogen in case of P-I as CTAB has been

removed (Fig. 3.11(a)). Instead, an N1s peak is readily detected for

P-DIDA-II due to the reaction of P-I and DIDA which gave the functional

group –N(COO-CH2CH3)2 (Fig. 3.11(b)) However the N1s regions has two

distinct components at 399.6 and 402.4 eV (in the 1:0.9 ratio)

assigned to free and protonated amine, respectively. Upon hydrolysis,

the ratio becomes 1:0.88 indicating a slight increase in

the protonated form (Fig. 3.11(c)).

Figure 3.11: High resolution N1s region for (a) P-I, (b) P-DIDA-II and (c) P-IDA-II.

395 400 405

3000

3500

4000

4500

5000

5500

(b)

(c)

(a)

I (c

ps)

Binding energy (eV)

54

Table 3.3: XPS data and % surface composition of P-MA and its derivatives.

Table 3.4: XPS data and % surface composition of P-I and its derivatives.

Polysiloxane

Element Si C O N I Cl N/Si

Core-line Si2p

102

C1s

285

O1s

532

N1s

399.5

I3d Cl2p 1:9

P-I/CTAB %Composition 15.1 57.4 22.4 2.0 3.0 -

P-I %Composition 25.9 32.0 40.0 - 1.5 0.6

P-DIDA-II %Composition 20.9 40.6 34.4 2.5 1.2 0.4

P-IDA-II %Composition 20.3 44.5 32.2 2.2 - 0.8

Polysiloxane

Element Si C O N + N+ Cl N/Si

Core-line Si2p

102

C1s

285

O1s

532

N1s

399.5

Cl2p

P-MA/CTAB %Composition 16.2 53.9 23.9 5.1 0.95

P-MA %Composition 25.0 27.2 39.2 5.85 1.7

P-DIDA-I %Composition 20.7 35.1 35.5 5.0 3.1

P-IDA-I %Composition 21.7 39.5 32.6 3.7 2.9

55

3.5 Thermal Analysis.

Thermogravimetric analysis (TGA) and defferential

thermogravimetric analysis (DTA) were examined for P-I/CTAB, P-I and

P-IDA and and its copper complex P-IDA-Cu under nitrogen atmosphere at

20 – 600 oC at rate 10

oC/minute. (Fig. 3.12) shows the thermograms of P-I

prepared in absence of CTAB ( Fig. 3.12(a)) and with presence of CTAB

(Fig. 3.12(b)) and that after CTAB was removed (Fig. 3.12(c)). It is found

that the thermogram for P-I prepared with absence of CTAB and that for

P-I, where CTAB was removad are very similar. Three peaks were

observed. The first preak occurs at ~75oC where P-I system lost 2 – 3.5 %

of it's initial weight . This attributed to lost of physisorbed water and

alcohol from the system pores [72,73]. The second peak at ~ 350 oC , where

the P-I system lost 34.5 %, which is probably due to degradation of

organofunctional groups bound to silicon atoms as well as dehydroxylation

and loss of water from silica . The third peak of temperature at

400 – 600 oC is due to further loss of 6% condensation of hydroxyl groups

form siloxane bonds (dehydroxylation). The total loss of weight of P-I

system were found in the range (42.5 – 44 %). The thermogram for

P-I/CTAB shows five peaks at 250 oC, 270

oC, 300

oC, 330

oC and 500

oC.

The two peaks at 250 oC and 300

oC were probably due to loss and

degradation of CTAB [72,73]. The total loss of weight for P-I/CTAB was

53.5 %. The high loss of weight for the P-I/CTAB compared with that of

P-I prepared without CTAB is due to amount of CTAB used.

56

Fig ( 3.12-a ):Thermogram of P-I prepared in absence of CTAB

Fig 3.12 (b): Thermogram of P-I prepared in presence of CTAB .

57

Fig 3.12 (c): Thermogram of P-I after CTAB was removed.

58

The thermograms of P-IDA shown in (Fig 3.13b) and P-IDA-copper

(II) complex showed three characteristic peaks at 70 oC, 220

oC and 430

oC

(Fig.3.13 (b)). The first peak occurs at ~75oC is attributed to lost of

physisorbed water and alcohol from the system pores [72-74].

The second peak is probably due to the decomposition and

degradation of the ligand functional groups. The third peak at 430 oC is

probably due to futher condensation and loss of water. The total loss of

copper complex (Fig. 3.13 (b)) is 23.1 % which is smaller than that of its

parent functionalized ligand precursur P-IDA (Fig.3.13(b)) (42.5%). This

provides evidence that this material becomes more stable upon

complexation with metal ions.

Fig 3.13 (a): Thermogram of P-IDA-II

59

Fig 3.13 (b): Thermogram of P-IDA-IIcopper (II) complex.

60

3.6 Metal Uptake Capacity.

3.6.1 Effect of Surfactant Concentration.

The metal ion uptake capacity was determined by batch method by

mixing the P-IDA–I or P-IDA-II polysiloxane ligand systems with

buffered solutions of copper metal ion. Measurements were carried out at

room temperature, pH 6 and 72 hours uptake time. Table 3.5 dipicted the

metal uptake capacity at different concentartions of surfactants with

respect to TEOS. It is shown that P-IDA-II showed higher metal uptake

capcaity than P-IDA-I. The highest metal uptake capacity of both

immobilized ligand system is shown in case of 1:8, surfactant :TEOS molar

ratio respicively which attibuted to presence of a well porous mesostructure

that caused by surfactant template synthesis.

Table 3.5: Copper uptake by P-IDA-I and P-IDA-II, pH=6, T=25 oC and =72 hrs.

CTAB/ TEOS * Type P-IDA-I P-IDA-II

0:1 A 0.230 0.630

1:32 B 0.382 1.031

1: 16 C 0.606 1.172

1:8 D 0.657 1.298

*molar ratio.

61

3.6.2 Effect of pH.

The effect of the pH on the uptake of Cu2+

metal ion by both

P-IDA-I (D) and P-IDA-II (D) is shown in (Fig 3.14). The results show an

increase of metal ion uptake with increasing pH reaching its maximum at

pH 6. Low uptake capacity occurs at lower pH values (pH = 3.5) due to

protonation of amine groups.

Figure 3.14: Uptake of Cu(II) by P-IDA-I (D) and P-IDA-II (D) versus pH values,

(T=25 o

C and t =72 hrs).

62

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 20 40 60 80

mm

ol C

u(I

I)/g

Lig

and

Tempretuer oC

3.6.3 Effect of Temperature on Metl Uptake of P-IDA-I.

The influence of temperature on Cu metal ions chemisorption by

P-IDA-I from aqueous solutions was investigated at different temperatures

(25-70) oC, at pH 6 by batch method. The results are presented in

(Figure 3.15) It is observed that the amount of metal ions extracted

increases with increasing of temperature. The curve indicates higher

affinity of the sorbent toward Cu metal ion by increasing of temperature

suggesting higher endothermic effect and increasing of mobility and

diffusion rate of this metal ion within the polysiloxane particles.

Fig 3.15: Uptake of Cu(II) by P-IDA-I (D) versus temperature.

63

3.6.4 Effect of Shaking.

A comparison between the metal ion uptake using shaking and

un-shaking at 70 oC was performed for P-IDA-II (A-D). The results are

given in (Table 3.6) In general shaking samples exhibit higher metal ion

uptake than un-shaking samples. This could be due to better diffusion of

the metal ion in case of shaken samples, as the ligand groups become more

accessible for the metal ions. Similar trends were reported for previously

prepared ligand systems [75].

Table 3.6: Copper uptake by P-IDA-II with and without shaking, pH=6, T=70 o

C and

t=72 hrs.

mmol Cu2+

/g ligand

Type CTAB/ TEOS

Shaken samples Unshaken samples

1.301 1.177 A 0:1

1.406 1.231 B 1:32

1.583 1.372 C 1: 16

1.658 1.398 D 1:8

3.6.5 Comparison Between the Uptake of Different Metal Ions.

The metal ion uptake capacity of Ni2+

, Cu2+

and Pb2+

by the

functionalized P-IDA-I and P-IDA-II immobilized ligand systems as

mmol M2+

/g ligand at the optimum conditions (T = 70 oC, pH = 6 and using

sample shaking) are given in (Table 3.7), It is clear that metal uptake

capacity of P-IDA-II is higher than P-IDA-I, this may be due to that

functional groups are more accessible in case of P-IDA-II than P-IDA-I.

64

It is clear that the uptake of metal ions increases in the order:

Cu2+

Ni2+

Pb2+

Table 3.7: Comparison between the uptake of different metal ions, T = 70 o

C, pH = 6,

t=72 hrs and using sample shaking.

mmol M (II)/g ligand

(P-IDA-II)

mmol M (II)/g ligand

(P-IDA-I)

Type

CTAB/

TEOS Cu (II) Ni (II) Pb (II) Cu (II) Ni (II) Pb (II)

1.301 0.358 0.072 1.263 0.134 0.027 A 0:1

1.406 0.37 0.141 1.304 0.230 0.074 B 1:32

1.583 0.40 0.186 1.397 0.345 0.112 C 1:16

1.658 0.553 0.338 1.509 0.399 0.241 D 1:8

3.6.6 Effect of Shaking Time

Measurements of metal uptake capacity of both P-IDA-I and

P-IDA-II for different metal ions (Ni2+

, Cu2+

and Pb2+

) were carried out at

different time intervals at the optimum conditions (T = 70 0

C, pH = 6 and

using shaking samples of 1:8 CTAB/TEOS mole ratio). The results are

given in Figures 3.(16-18). It is shown that the metal ion uptake is

increased as a function of shaking time and reached equilibrium nearly

after 24 hours where maximum uptake is obtained.

65

0

0.1

0.2

0.3

0.4

0.5

0.6

0 20 40 60 80

mm

ol N

i(II

)/g

ligan

d

Time (Hours) P-IDA-II P-IDA-I

Figure 3.16: Cu(II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time

(pH=6, T= 70 oC and using shaking samples).

Figure 3.17: Ni(II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time

(pH=6, T= 70 0

C and using shaking samples).

66

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 20 40 60 80

mm

ol P

b (

II)

/g L

igan

d

Times (Hours)

P-IDA-II P-IDA-I

Figure 3.18: Pb(II) uptake by P-IDA-I (D) and P-IDA-II (D) versus time

(pH=6, T= 70 0

C and using shaking samples).

67

Conclusion

In this study insoluble iminodiacetic acid polysiloxane immobilized

ligand systems, have been prepared by template sol-gel method in presence

of CTAB surfactant.

The sol-gel process is summarized in hydrolytic polycondensation of

TEOS and an appropriate silane coupling agent. The

3-aminopropylpolysiloxane and 3-iodopropylpolysiloxane were primarily

prepared by this method followed by systematic chemical modification to

obtain the desired iminodiaacetic acid functionalized ligand systems in two

routes.

In the first route preparation was achieved by modification of

3-aminopropyllpolysilocxane with ethylchloroacetate followed by

hydrolysis of the ethoxy groups. The second route was achieved by the

reaction of 3-iodopropylpolysiloxane with diethyliminodiacetate followed

by hydrolysis of the ethoxy groups.

These polysiloxane immobilized ligand systems were well

characterized by a variety of physical techniques.

FTIR provided strong qualitative evidences about the functional

groups of the immobilized ligands.

High-resolution 13

C CP-MAS NMR provided essential information

on the structural nature of the pendent ligand groups.

XPS technique provided valuable information about the surface

chemical composition for these immobilized ligand systems.

TGA and TDG thermal analysis confirmed that these immobilized

ligand systems are highly thermal stable even at high temperatures

(up to 250 0C). Very High temperatures disrupt the polysiloxane matrix and

cause pyrolysis and modification of the structural properties.

68

Elemental analysis provided the exact content of the functionalized

ligand groups that attached to the immobilized ligand systems.

These immobilized ligand systems exhibit high potential for

preconcentration of divalent metal ions (Ni2+

, Cu2+

and Pb2+

)

from aqueous solutions.

The optimum experimental conditions that studied showed that

maximum uptake could be attained at pH 6 for 48 hours shaking at 70oC.

69

REFERENCES

1- J. O. Duruibe, M. O. C. Ogwuegbu and J. N. Egwurugwu, Heavy metal

pollution and human biotoxic effects. Int. J. Phys. Sci. 2007, 2 (5),

112-118.

2- M.A. Momodu and C.A. Anyakora., Heavy Metal Contamination of

Ground Water: The Surulere Case Study., Res J Environ Earth Sci.,

2010, 2(1), 39-43.

3- L. Malachowski, J. L. Stair, and J. A. Holcombe, Immobilized

peptides/amino acids on solid supports for metal remediation, Pure

Appl. Chem., 2004, 76 (4), 777–787.

4- N.M. El-Ashgar, Extraction and Preconcentration Capacity of

Bifunctionalized Diamine-Thiol Polysiloxane Immobilized Ligand

System Towards Some Divalent Cations. J. Iran. Chem. Soc., 2008,

6(4), 823-830.

5- S. K. Muzyed, Heavy Metal Concentrations in Commercially

Available Fishes in Gaza Strip Markets, M.Sc. thesis, Islamic

University, 2011.

6- K. Mortazavi, M. Ghaedi, M. Roosta and M. Montazerozohori.,

Chemical functionalization of silica gel with 2-((3-silylpropylimino)

methyl) phenol (SPIMP) and its application for solid phase

extraction and preconcentration of Fe (III), Pb (II), Cu (II), Ni (II),

Co (II) and Zn (II) Ions., Indian J.Sci.Technol., 2012, 5(1), ISSN:

0974- 6846.

7- R. K. Sharma., Design, synthesis, and application of chelating

polymers for separation and determination of trace and toxic metal

ions. A green analytical method. Pure Appl. Chem., 2001, 73 (1),

181–186.

70

8- J. L. Stair, Synthesis and Characterization of Short Chain Peptides

for use in Metal Remediation and Preconcentration,

Ph.D. thesis 2006.

9- M. A. Hughes, The Structure Function Relationship of Silica

Polyamine Composites, PhD Thesis, ProQuest Informayion

and Learning Company, 2007

10- D. W. Hall, J. A. Sandrin, and R. E. McBride, An overview of solvent

extraction treatment technologies. Environmental Progress, 1990,

9(2), 98-105.

11- K. E.Geckeler, and K. Volchek, Removal of Hazardous Substances

from Water Using Ultrafiltration in Conjunction with Soluble

Polymers. Environ. Sci. Technol., 1996, 30(3), 725-734.

12- K. E. Geckeler, E. Rosenberg, and Editors. Functional Nanomaterials.

American Scientific Publishers, Valencia, USA, 2006, 488.

13- S. D. Alexandratos, and D. W. Crick, Polymer-Supported Reagents:

Application to Separation Science, Ind. Eng. Chem. Res., 1996,

35(3), 635-644.

14- R. A. Beauvais, and S. D. Alexandratos, Polymer-supported reagents

for the selective complexation of metal ions: an overview, React.

Funct. Polym., 1998, 36(2), 113-123.

15- N. M. El-Ashgar, I. M. El-Nahhal, M. M. Chehimi, F. Babonneau and

J. Livage, A new route synthesis of immobilized-polysiloxane

iminodiacetic acid ligand system, its characterization and

applications, Mater. Lett., 2007, 61, 4553-4558.

16- N. M. El-Ashgara, I.M. El-Nahhalb, M. M. Chehimic, F. Babonneaud

and J. Livage, Preparation of ethylenediaminetriacetic acid silica-gel

immobilized ligand system and its application for trace metal

71

analysis in aqueous samples, Intern. J. Environ. Anal. Chem., 2009,

89(14), 1057-1069.

17- M. Ghaedi, M. Rezakhani, S. Khodadoust, K. Niknam, and M. Soylak,

The Solid Phase Extraction of Some Metal Ions Using Palladium

Nanoparticles Attached to Silica Gel Chemically Bonded by Silica-

Bonded N-Propylmorpholine as New Sorbent prior to Their

Determination by Flame Atomic Absorption Spectroscopy, The

Scientific World Journal, 2012(2012)

18- R. Qu, M. Wang, C. Sun, Y. Zhang, C. Ji, H. Chen, Y. Meng and

P. Yin, Chemical modification of silica-gel with hydroxyl- or amino-

terminated polyamine for adsorption of Au(III), Appl. Surf. Sci.,

2008, 255(5), 3361–3370.

19- M. A. Abu-Daabes, N. G. Pinto, Synthesis and characterization of a

nano-structured sorbent for the direct removal of mercury vapor

from flue gases by chelation, Chem. Eng. Sci., 2005, 60(7),

1901–1910.

20- A.Goswami and A. K. Singh, Silica gel functionalized with

resacetophenone: synthesis of a new chelating matrix and its

application as metal ion collector for their flame atomic absorption

spectrometric determination, Anal. Chim. Acta, 2002, 454(2),

229-240.

21- N. M. El-Ashgar, I. M. El-Nahhal, M. M. Chehimi, F. Babonneau and

J. Livage, Synthesis of Polysiloxane-Immobilized Monoamine,

Diamine, and Triamine Ligand Systems in the Presence of CTAB

and Their Applications, Phosphorus, Sulfur, and Silicon and the

Related Element, 2012, 187(3), 392-402.

72

22- N. M. El-Ashgar, I. M. El-Nahhal, M. M. Chehimi, F. Babonneau and

J. Livage, New Strategy for the Synthesis of Diethylnetriamine-

tetraacetic Acid Functionalized Polysiloxane Ligand System, J. of

Dispersion Science and Technology, 2009, 30(5), 684-690 .

23- N. M. El-Ashgar and M. S. Abdel-Latif, Synthesis and Applications of

a New Polysiloxane-Immobilized Macrocyclic Ligand System,

Analytical Letters, 2008, 41, 3074–3087.

24- M. Zougagh, J. M. Cano Pavon, A. Garcia de Torres, Chelating

sorbents based on silica gel and their application in atomic

spectrometry, Anal Bioanal Chem., 2005, 381(6), 1103–1113.

25- I. M. El-Nahhal and N. M. El-Ashgar, A review on polysiloxane-

immobilized ligand systems: Synthesis, characterization and

applications, J. Organomet. Chem., 2007, 692, 2861-2886.

26- C.E. Carraher, Polymer Chemistry, An Introduction, 4th ed., Marcel

Dekker, Inc., 1996.

27- R. J. Kvitek, J. F. Evans, P.W. Carr, Diamine/Silane-Modified

controlled pore glass: The covalent attachment reaction from

aqueous solution and the mechanism of reaction of bound diamine

with copper(II), Anal Chim Acta, 1982, 144, 93-106.

28- S. Ünal, Preconcentration of Rare Earth Elements (REEs) using

silica gel modified with several functional groups, Izmir Institute of

Technology, master thesis, 2007.

29- S. M. Saadeh and N. M. El-Ashgar, Preparation of Immobilized

Polysiloxaneimino(2-aminoethylacetamide) and its Application, The

Islamic University Journal, (Series of Natural Studies and

Engineering), 2006, 14(1), 37-50.

73

30- N.M. El-Ashgar,Synthesis and Applications of some Polysiloxane-

Immobilized Ligand System, M. Sc., Thesis, Al-Azhar University,

1999.

31- N.M. El-Ashgar, I.M. El-Nahhal, Preconcentration and Separation

of Copper(II) by 3-Aminopropylpolysiloxane Immobilized Ligand

System, J. Sol–Gel Sci. Technol.,2005, 34 (2), 165-172.

32- A.A. El-Nasser, R.V. Parish, Solid polysiloxane ligands containing

glycine- or iminodiacetate-groups: synthesis and application to

binding and separation of metal ions, J. Chem. Soc., Dalton Trans.,

1999, 19, 3463-3466.

33- N.M. El-Ashgar, I.M. El-Nahhal, M.M. Chehimi, F. Babonneau, J.

Livage, Synthesis and Structural Characterization of a New

Macrocyclic Polysiloxane-immobilized Ligand System, Monatsh.

Chem., 2006, 137(3), 263-275.

34- N.M. El-Ashgar, I.M. El-Nahhal, M.M. Chehimi, M. Delmar,

F. Babonneau, J. Livage, Extraction of metal ions (Fe3+

, Co2+

, Ni2+

,

Cu2+

and Zn2+

) using immobilized-polysiloxane iminobis(n-2-

aminophenylacetamide) ligand system, J. Sol–Gel Sci. Technol.,

2007, 41(1), 3-10.

35- F.R. Zaggout, I.M. El-Nahhal, S.M. Zourab, N.M. El-Ashgar, H.

Mottaweh, Encapsulation of Methyl Red pH‐Indicator into a Sol‐Gel

Matrix, J. Disper. Sci. Technol., 2005, 26(5), 629-633.

36- N. M. El-Ashgar and S. M. Saadeh, Preparation of Immobilized-

Polysiloxane Salicylaldehyde Propylimine and Its Application, J.

Al-Aqsa Unv., 2006, 10, 153-161.

74

37- I.M El-Nahhal, N.M. El-Ashgar, M.M. Chehimi, P. Bargiela, J.

Maquet, F. Babonneau and J. Livage, Metal uptake by porous

iminobis (N-2-aminoethylacetamide)-modified polysiloxane ligand

system, Microp. Mesop, Mat., 2003, 65(2-3), 299-310.

38- P. Kortesuo, Sol-gel derived silica gel monoliths and microparticles

as carrier in controlled drug delivery in tissue administration,

Helsinki, Academic Dissertation, 2001.

39- C.A. Milea, C. Bogatu and A. Duta, The influence of Parameters in

Silica Sol-Gel Process, Engineering Sciences, 2011, 4 (53)1.

40- X. Liu, Dendrimer Templated Silica Networks: Synthesis,

Characterization and Application in Silver Nanoparticle

Construction, master thesis, McGill University, 2008.

41- E. J. Nassar, K. J. Ciuffi1, P. S. Calefi1, L. A. Rocha1, E. H. De Faria,

M. L. A. Silva, P. P. Luz, L. C. Bandeira, A. Cestari and C. N.

Fernandes, Biomaterials and Sol-Gel Process: A Methodology for

the Preparation of Functional Materials, Biomaterials Science and

Engineering, 2011.

42- N. M. El-Ashgar, Synthesis and Characterization of some

Polysiloxane Systems and their Applications, Ph.D.Thesis, Ain

Shams, 2002.

43- A.Mujahid, P. A. Lieberzeit, and F. L. Dickert, Chemical Sensors

Based on Molecularly Imprinted Sol-Gel Materials. Materials.

2010, 3(4), 2196-2217.

44- L. Kind, Template directed synthesis of highly organized functional

biomimetic silica nanostructures, Ph.D. thesis, Basel 2009.

75

45- J. Y. Kim, S. B.Yoon, and J. S. Yu, Template Synthesis of a New

Mesostructured Silica from Highly Ordered Mesoporous Carbon

Molecular Sieves, Chem. Mater. 2003, 15, 1932-1934.

46- J. A. Baea, K. Songb, J. Jeonb, Y. S. Kob, Y. Parkc and J. Yim, Effect

of pore structure of amine-functionalized mesoporous silica-

supported rhodium catalysts on 1-octene hydroformylation,

Microporous and Mesoporous Materials, 2009, 123(1–3), 289–297.

47- F. Adam and T. Chew, A Facile Template-Free Room Temperature

Synthesis of Mesoporous Wormlike Nickel Phyllosilicate, The Open

Colloid Science Journal, 2012, 5, 1-4.

48- A. Z. Abdullah, N. Razali and K. T. Lee, Influence of the Silica-to-

Surfactant Ratio and the pH of Synthesis on the Characteristics of

Mesoporous SBA-15, Journal of Physical Science, 21(2),

13–27, 2010.

49- C. Gao, Formation mechanism of anionic-surfactant-templated

mesoporous silica (AMS), Stockholm, 2009.

50- J. Jiua, K. Kurumadab, F. Wanga and L. Peia, Syntheses of highly

ordered mesoporous silica by new hybrid template, Mater. Chem.

Phys., 2004, 86( 2–3), 435–439.

51- F. Kleitz, W. Schmidt and F. Schüth, Calcination behavior of

different surfactant-templated mesostructured silica materials,

Microporous Mesoporous Mater., 2003, 65(1), 1–29.

52- F. Hof, S. L. Craig, C. Nuckolls and J. Rubek, Molecular

Encapsulation, Angew. Chem. Int. Ed. Engl., 2002, 41(9),

1488-1508.

76

53- C.-Y. Su, M. D. Simth and H.-C. Loyle, Columnar Supramolecular

Architecture Self-Assembled from S4-Symmetric Coordination

Nanotubes Encapsulating Neutral Guest Molecules, Angew. Chem.,

Int. Ed. Engl., 2003, 42(34), 4085-4089.

54- P. J. Branton, P. G. Hull and K. S. W. King, Physisorption of nitrogen

and oxygen by MCM-41, a model mesoporous adsorbent, J. Chem.

Soc., Chem. Commun., 1993, 16, 1257-1258.

55- K. Moller and T. Bein, Inclusion Chemistry in Periodic Mesoporous

Hosts, Chem. Mater., 1998, 10(10), 2950-2963.

56- J.L. Salager, Surfactants types and uses, Mérida-Venezuela, 2, 2002.

57- D.J. Shaw and W.H. Butter, Introduction to Colloid and Surface

Chemistry, Oxford, 4th Edition, 1992

58- S. E. Rankin, B. Tan, H. J. Lehmler, K. P. Hindman and B. L. Knutson,

Well-ordered mesoporous silica prepared by cationic fluorinated

surfactant templating, Microporous Mesoporous Mater., 2004, 73,

197–202.

60- B. N. Nair, W. J. Elferink, K. Keizer, and H. Verweij, Sol–Gel

Synthesis and Characterization of Microporous Silica Membranes I:

SAXS Study on the Growth of Polymeric Structures, J. Colloid

Interface Sci.,1996,178(2), 565–570.

61- B. Hatton, K. Landskron, W. Whitnall, D. Perovic and G. A. Ozin,

Past, Present, and Future of Periodic Mesoporous Organosilicas

The PMOs, Acc. Chem. Res., 2005, 38(4), 305-312.

62- A.Y. Ku, D. A. Saville and I. A. Aksay, Electric-Field-Induced

Orientation of Surfactant-Templated Nanoscopic Silica, Langmuir,

2007, 23, 8156-8162.

77

63- Y. M. Setoguchi, Y. Teraoka, I. Moriguchi, S. Kagawa, N. Tomonaga,

A. Yasutake and J. Izumi, Rapid Room Temperature Synthesis of

Hexagonal Mesoporous Silica Using Inorganic Silicate Sources and

Cationic Surfactants under Highly Acidic Conditions, J. Porous

Mater., 1997, 4(2), 129-134.

64- S. Shio, A. Kimura, M. Yamaguchi, K. Yoshida and K. Kuroda,

Morphological control of ordered mesoporous silica: formation of

fine and rod-like mesoporous powders from completely dissolved

aqueous solutions of sodium metasilicate and cationic surfactants,

Chem. Commun., 1998,22, 2461-2462.

65- A. Berggren, A. E. C. Palmqvist and K. Holmberg, Surfactant-

templated mesostructured materials from inorganic silica , Soft

Matter, 2005, 1(3), 219-226.

66- I. Ahmed, R.V. Parish, Insoluble ligands and their applications : IV.

Polysiloxane-bis(2-aminoethyl)amine ligands and some derivatives,

J. Organomet. Chem., 1993, 452, (1–2), 23–28.

67- B. Arkles, J. R. Steinmetz, J. Zazyezny, and P. Mehta, Factors

Contributing to the Stability of Alkoxysilanes in Aqueous Solution,

Silanes and other coupling agents, (1992), 91-104.

68- I. M. El-Nahhal, J. J. Yang, I. S. Chuang, G. E. Maciel, G. E., Synthesis

and solid-state NMR structural characterization of polysiloxane-

immobilized thiol and thiol-amine ligands, J. Non-Cryst. Solids,

1996, 208(1-2), 105-118.

69- J.J. Yang, I. M. El-Nahhal, I.S. Chuang, and G.E. Maciel, Synthesis

and solid-state NMR structural characterization of polysiloxane-

immobilized phosphine-amine and phosphine-thiol ligand systems ,

J. Non-Cryst. Solids, 1997, 212(2-3), 281-291.

78

70- I. M. El-Nahhal, F. R. Zaggout and N. M. El-Ashgar, Uptake of

Divalent Metal Ions (Cu2+

, Zn2+

and Cd2+

) by Polysiloxane

Immobilized Monoamine Ligand System, Anal. Letters, 2000, 33(10),

2031-2053.

71- G. V. Kudryavtsev, D. V. Miltchenko, V. V. Yagov and A. A.

Lopatkin, Ion sorption on modified silica surface, Colloid Interface

Sci., 1990, 140(1), 114-122.

72- A. M. Klonkowski, K. Koehler, and C. W. Schlaepfer, Copper(II) in

organically modified silicate gels prepared by the sol–gel method.

Bulk complexed gels, J. Mater. Chem., 1993, 3(1), 105-110.

73- A. M. Klonkowski, T. Widernik and B. Grobelna, Amino-Modified

Silicate Xerogels Complexed with Cu(II) as Catalyst Precursors.

Coordination State and Thermal Decomposition, J. sol-gel sci. tech.,

2001, 20(2), 161-180.

74- A. M. Klonkowski, K. Koehler, and C. W. Schlaepfer, Copper(II) in

organically modified silicate gels prepared by the sol–gel method.

Bulk complexed gels, J. Mater. Chem., 1993, 3(1), 105-110.

75- I. M. El-Nahhal, B. A. El-Shetary, K. A. R. Salib, N. M. El-Ashgar and

A. M. El-Hashash, Uptake of divalent metal ions (Cu2+

, Ni2+

and

Co2+

) by polysiloxane immobilized triamine-thiol and thiol-acetate

ligand system, Anal. Lett., 2001, 34(12), 2189-2202.