liquid–liquid equilibria for the quaternary system h 3 po ...

6
Liquid-Liquid Equilibria for the Quaternary System H 3 PO 4 -NaCl- H 2 O-TBP at 298.15 K Chengqi Liu, Yongsheng Ren,* and Yanan Wang Department of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, PR China ABSTRACT: The equilibrium data of quaternary system phosphoric acid + sodium chloride + water + tri-n-butyl phosphate (TBP) was discussed at 298.15 K and atmospheric pressure. It was investigated experimentally in the mass concentration range 0-15% of NaCl and 4-24% of H 3 PO 4 in the initial aqueous phase. The experimental results show that the separation factor of H 2 O and the distribution coecient of H 3 PO 4 increase when the content of H 3 PO 4 increases. The separation factor of NaCl decreases after an increase to a maximum value. Moreover, it was found out that the mass ratio of ternary system H 3 PO 4 -NaCl-H 2 O to the saturation point. It would separate easily when the mass percent of NaCl occupies more than 12% in the system. The experimental tie-line data was correlated with the nonrandom two-liquid activity coecient model. 1. INTRODUCTION Phosphoric acid is widely used in many areas as a basic raw material. 1 There are two methods to produce phosphoric acid. One is a thermal method, and the other is a wet process. Although the impurity content is lower by using the thermal method, this method consumes a lot of energy and incurs high production costs. Moreover, it has serious impact on the environment. The wet method has many advantages, such as it needs less power consumption, the equipment is easy to solve, it facilitate operation management, and has a low production cost, so that many countries in the world are trying to purify wet-process phosphoric acid to satisfy the requirement of producing high purity phosphoric acid. There are multiple ways of purifying wet-process phosphoric acid, for example, chemical precipitation, 2 ion exchange, 3 and a crystallization process. 4 However, those methods have many limitations such as high cost, a complex purication process, and serious environmental pollution. It is dicult to meet the demand in the industry and further theoretical studies are needed. Solvent extraction process is adopted for its user-friendly control, safety production, environmental conservation, and economy. The method has obvious advantages of its application and it is extensively used. The core of extraction lies in the selection of extraction agent. Nowadays, many equilibrium data for the aqueous mixtures of phosphoric acid with organic solvents, such as isoamyl acetate, methyl isoamyl ketone, cyclohexane, methylcyclohexane, toluene and tri-n-butyl phosphate (TBP), have been reported by several research- ers. 5-8 TBP is a neutral extraction agent. It can react in an inorganic complexation reaction. The TBP can, for example, complex with acids in a ratio of 1:1 or 1:3, or complex with water in a 1:1 ratio. 9 Liquid-liquid equilibrium data is important for designing extraction equipment, evaluating the important parameters of the extraction process, and enlarging the database of the simulation process. Using a small amount of experimental data on liquid-liquid equilibrium data correlation and prediction within the range of measurement is very necessary. This research focuses on the determination of the basic data of the quaternary system H 3 PO 4 -NaCl-H 2 O-TBP obtaining liquid-liquid equilibria at 298.15 K and atmospheric pressure. The mass compositions were measured. Distribution coef- cients of H 3 PO 4 and separation factors of H 2 O and NaCl are determined from tie-line data. The experimental data was correlated using the nonrandom two-liquid (NRTL) activity coecient model. 2. EXPERIMENTAL SECTION 2.1. Materials. Phosphoric acid (Sigma, 85%) and sodium chloride were used as received. TBP was provided by the Aoda Chemical Company, China, and was used without any further purication. All of the reagents were analytical grade. Double distilled water was used in the experiments. 2.2. Procedure. The experiments were carried out at T= (298.15 ± 0.01) K at atmospheric pressure with a thermostat. In the initial aqueous phase of the H 3 PO 4 -NaCl-H 2 O-TBP quaternary system, the concentration range of phosphoric acid started at ω (mass fraction) = 0.04% and increased at four percent intervals. The concentration of sodium chloride was from 0 to 0.15%. The TBP was mixed with the initial aqueous phase in a 250 mL conical ask which was sealed with cling lm. The mixture was shaken for an hour at constant Received: September 10, 2013 Accepted: December 17, 2013 Article pubs.acs.org/jced © XXXX American Chemical Society A dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX-XXX

Upload: yanan

Post on 21-Dec-2016

217 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

Liquid−Liquid Equilibria for the Quaternary System H3PO4−NaCl−H2O−TBP at 298.15 KChengqi Liu, Yongsheng Ren,* and Ya’nan Wang

Department of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, PR China

ABSTRACT: The equilibrium data of quaternary system phosphoric acid +sodium chloride + water + tri-n-butyl phosphate (TBP) was discussed at 298.15K and atmospheric pressure. It was investigated experimentally in the massconcentration range 0−15% of NaCl and 4−24% of H3PO4 in the initialaqueous phase. The experimental results show that the separation factor of H2Oand the distribution coefficient of H3PO4 increase when the content of H3PO4increases. The separation factor of NaCl decreases after an increase to amaximum value. Moreover, it was found out that the mass ratio of ternarysystem H3PO4−NaCl−H2O to the saturation point. It would separate easilywhen the mass percent of NaCl occupies more than 12% in the system. Theexperimental tie-line data was correlated with the nonrandom two-liquid activitycoefficient model.

1. INTRODUCTION

Phosphoric acid is widely used in many areas as a basic rawmaterial.1 There are two methods to produce phosphoric acid.One is a thermal method, and the other is a wet process.Although the impurity content is lower by using the thermalmethod, this method consumes a lot of energy and incurs highproduction costs. Moreover, it has serious impact on theenvironment. The wet method has many advantages, such as itneeds less power consumption, the equipment is easy to solve,it facilitate operation management, and has a low productioncost, so that many countries in the world are trying to purifywet-process phosphoric acid to satisfy the requirement ofproducing high purity phosphoric acid.There are multiple ways of purifying wet-process phosphoric

acid, for example, chemical precipitation,2 ion exchange,3 and acrystallization process.4 However, those methods have manylimitations such as high cost, a complex purification process,and serious environmental pollution. It is difficult to meet thedemand in the industry and further theoretical studies areneeded.Solvent extraction process is adopted for its user-friendly

control, safety production, environmental conservation, andeconomy. The method has obvious advantages of its applicationand it is extensively used. The core of extraction lies in theselection of extraction agent. Nowadays, many equilibrium datafor the aqueous mixtures of phosphoric acid with organicsolvents, such as isoamyl acetate, methyl isoamyl ketone,cyclohexane, methylcyclohexane, toluene and tri-n-butylphosphate (TBP), have been reported by several research-ers.5−8 TBP is a neutral extraction agent. It can react in aninorganic complexation reaction. The TBP can, for example,complex with acids in a ratio of 1:1 or 1:3, or complex withwater in a 1:1 ratio.9

Liquid−liquid equilibrium data is important for designingextraction equipment, evaluating the important parameters ofthe extraction process, and enlarging the database of thesimulation process. Using a small amount of experimental dataon liquid−liquid equilibrium data correlation and predictionwithin the range of measurement is very necessary.This research focuses on the determination of the basic data

of the quaternary system H3PO4−NaCl−H2O−TBP obtainingliquid−liquid equilibria at 298.15 K and atmospheric pressure.The mass compositions were measured. Distribution coef-ficients of H3PO4 and separation factors of H2O and NaCl aredetermined from tie-line data. The experimental data wascorrelated using the nonrandom two-liquid (NRTL) activitycoefficient model.

2. EXPERIMENTAL SECTION

2.1. Materials. Phosphoric acid (Sigma, 85%) and sodiumchloride were used as received. TBP was provided by the AodaChemical Company, China, and was used without any furtherpurification. All of the reagents were analytical grade. Doubledistilled water was used in the experiments.

2.2. Procedure. The experiments were carried out at T=(298.15 ± 0.01) K at atmospheric pressure with a thermostat.In the initial aqueous phase of the H3PO4−NaCl−H2O−TBPquaternary system, the concentration range of phosphoric acidstarted at ω (mass fraction) = 0.04% and increased at fourpercent intervals. The concentration of sodium chloride wasfrom 0 to 0.15%. The TBP was mixed with the initial aqueousphase in a 250 mL conical flask which was sealed with clingfilm. The mixture was shaken for an hour at constant

Received: September 10, 2013Accepted: December 17, 2013

Article

pubs.acs.org/jced

© XXXX American Chemical Society A dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Page 2: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

temperature and then allowed to sit for one hour to completelyseparate the to two liquid phases; the organic phase is superiorand the aqueous phase in inferior.The two liquids were separated in a separatory funnel, care

being taken to carefully leave a layer of aqueous solution at least1 cm below the interface. Then the remaining aqueous layer aswell as at least 1 cm thick of the organic phase in the separatoryfunnel was collected carefully in a 10 mL buret, in order tomake the sample of superior phase without contaminationbecome possible. The volume of the liquids in the buret wasrecorded and calculated into mass by using densities. Thencomposition analysis was respectively carried out in the twophases. Phosphoric acid concentration in the aqueous phasewas measured by the quinoline phosphomolybdate gravimetricmethod.10 Chloridion concentrations in both phases weredetermined by the Volhard method.11 Water in the organicphase was measured by the Karl Fischer apparatus.12,13 Thedensities of the two phases were determined by pycnometer.14

Phosphoric acid and water concentrations in the organic phaseand TBP concentrations in both phases could be calculated bymaterial balance. At least three parallel samples were carried outin each experiment. All results were expressed in mass fractions.The precision for volume, mass, and density is ± 0.1 mL, ±0.0001 g, ± 0.0001 g·mL−1, respectively, and the combineduncertainty is less than 0.03.15 All the determinations wererepeated three times to check reproducibility, and then anaverage value was given.

3. RESULTS AND DISCUSSION

The experimental results are shown in Table 1. Allconcentrations are expressed in ωi

ϕ, where i stands for thecomponent (i = 1 for phosphoric acid, i = 2 for sodiumchloride, i = 3 for water, i = 4 for TBP) and φ stands for thephase (φ = a for the aqueous phase and φ = o for the organicphase). Table 1 includes the compositions of the initialmixtures and equilibrium phases at 298.15 K. The initialaqueous phase contains mass fraction of 0.04 to 0.24phosphoric acid and 0.0 to 0.15 sodium chloride.Table 1 shows that the TBP in the aqueous phase is very

small. The combination of phosphoric acid with TBP is morethan sodium chloride. As phosphoric acid increases in the initialmixed phase, the content in the organic phase also increases.The case is the same for sodium chloride. In the experiment,the aqueous phase cannot dissolve NaCl completely when themass fraction of NaCl occupies more than 12% in the system.Distribution coefficient refers to the ratio between total

concentration of extracted substance in the organic phase andthat in the aqueous phase. It changes over experimentalconditions such as concentration of extracted substance, acidityof the solution, extractant concentration, and nature of diluentand so on. The material of high distribution coefficient moreeasily transfers from the aqueous phase to the organic phase.On the contrary, the material of the small distributioncoefficient exists in the aqueous phase. Thus, substances canbe separated. The extraction rate refers to the extraction ofmaterial into the organic phase of the two-phase percentage ofthe total. It indicates the extent of extraction. The greaterdistribution coefficient causes the higher extraction rate.The equations are shown as follows,

=DDDi

i

i

o

a(1)

=SDDi

i1,

1

(2)

In the equations, D stands for distribution coefficient and Sstands for separation factor; i stands for the material (i = 1 forphosphoric acid, i = 2 for sodium chloride, i = 3 for water, i = 4for TBP) and “a” stands for the aqueous phase, “o” stands forthe organic phase.16 Equations 1 and 2 can be used to calculatethe values in Table 1.The diagram shows that the distribution coefficient of

phosphoric acid and separation factor of water are increasinggradually when the concentration of sodium chloride isinvariant. The variation trend is shown in Figure 1, Figure 2,and Figure 3. The phosphoric acid composition in the initialaqueous phase is plotted on the x-axis.Figure 1 displays that when the phosphate content is

constant, the distribution coefficient is increasing with theincrease of sodium chloride composition. Meanwhile, when thesodium chloride content is constant, the distribution coefficientis also increasing with the increase of phosphoric acidcomposition. The reason for the increase of D1 is thatphosphoric acid transfers into the organic phase only in aneutral form rather than a dissociated form.17 As thephosphoric acid concentration increases, the proportion ofundissociated phosphoric acid increases.In Figure 2, the results indicate that when the sodium

chloride composition is between ω = 0.03 and 0.05, theseparation factor of sodium chloride (S1,2) decreases, S1,2increases to a maximum value with ω = 0.08 phosphoric acidand then decreases with a further increase in the phosphoricacid concentration, S1,2 increases to a maximum value with ω =0.12 phosphoric acid in the presence of ω = 0.10 to 0.13sodium chloride, when sodium chloride concentration is 0.15,S1,2 increases to a maximum value with ω = 0.16 phosphoricacid and then decreases.In Figure 3, the results indicate that S1,3 increases with an

increase in phosphoric acid concentration in the presence of ω= 0 to 0.15 sodium chloride. When the concentration ofsodium chloride remains unchanged, S1,3 also increases. In theliterature,18 the concentration ranges are from ω (massfraction) = 0.028 to 0.20 for phosphoric acid and ω = 0 to0.25 for calcium chloride in the initial aqueous phase; in ourresearch, ω = 0 to 0.15 for sodium chloride and ω = 0.04 to0.24 for phosphoric acid in the initial aqueous phase. Acomparison of the data of the same concentration range (ω = 0to 0.15) of calcium chloride in the literature with theexperimental data shows that the trend of densities of thetwo phases and distribution coefficient of phosphoric acid areidentical, the distribution coefficient of phosphoric acid is from0.07 to 0.56 in ref 18 and changes from 0.05 to 0.53 in ourexperimental data. It demonstrates that the distribution ofphosphoric acid in the two phases has certain regularity.The the nonrandom two-liquid (NRTL) model of Renon

and Prausnitz can be used for the association of a strongly polarsystem.19 The biggest advantage is that it can be used forcorrelation evaluation of the partially miscible system. H3−PO4−NaCl−H2O−TBP quaternary system is the partiallymiscible system and contains salt, which belongs to the strongpolarity system. Using NRTL is relatively appropriate. In thismodel, the first material is phosphoric acid, the second issodium chloride, and the third is water.

Journal of Chemical & Engineering Data Article

dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXXB

Page 3: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

Table1.Liqu

id−Liqu

idEqu

ilibriain

theSystem

H3PO

4(1)−

NaC

l(2)−H

2O(3)−

TBP(4)andthePhysicalR

esultof

DistributionCoefficientandSeparation

Factor

at298.15

Kand101.325kP

aa

initialmixtures

aqueousphase

organicphase

ρaρo

ω1

ω2

ω3

ω4

ω1

ω2

ω3

ω4

(g·mL−

1 )ω

4(g·mL−

1 )D

1D

2S 1

,2D

3S 1

,3

NaC

l=0.0in

InitialAqueous

Phase

1.99

0.00

48.11

49.90

3.99

0.00

94.80

1.21

1.0203

0.20

0.00

6.46

93.34

0.9762

0.0501

0.0681

0.7360

3.89

0.00

46.21

49.90

7.68

0.00

89.59

2.72

1.0424

0.45

0.00

6.68

92.87

0.9809

0.0581

0.0746

0.7792

5.88

0.00

44.22

49.90

11.05

0.00

87.30

1.65

1.0605

1.33

0.00

6.52

92.15

0.9837

0.1200

0.0747

1.6059

7.78

0.00

42.32

49.90

14.04

0.00

83.97

1.99

1.0814

2.38

0.00

6.68

90.94

0.9891

0.1696

0.0796

2.1316

9.77

0.00

40.33

49.90

17.78

0.00

81.98

0.24

1.1052

3.28

0.00

6.61

90.11

0.9964

0.1844

0.0807

2.2860

11.66

0.00

38.49

49.85

20.84

0.00

78.04

1.13

1.1278

4.00

0.00

5.66

90.34

1.0011

0.1920

0.0725

2.6466

NaC

l=0.03

inInitialAqueous

Phase

1.99

1.30

46.87

49.85

3.88

2.80

91.59

1.73

1.0405

0.26

0.01

6.17

93.57

0.9768

0.0664

0.0039

17.1514

0.0673

0.9860

3.89

1.30

44.91

49.90

7.44

2.62

89.36

0.58

1.0597

0.81

0.02

6.34

92.82

0.9816

0.1093

0.0083

13.1296

0.0710

1.5397

5.87

1.30

42.98

49.85

10.61

2.64

86.20

0.55

1.0835

1.83

0.05

6.14

91.98

0.9843

0.1727

0.0174

9.8995

0.0713

2.4228

7.78

1.30

41.02

49.90

14.08

2.46

82.47

1.00

1.1011

2.44

0.04

5.94

91.58

0.9926

0.1731

0.0179

9.6656

0.0721

2.4025

9.76

1.30

39.09

49.85

17.68

2.85

78.61

0.86

1.1204

3.05

0.08

5.75

91.12

0.9963

0.1726

0.0281

6.1493

0.0731

2.3590

11.67

1.30

37.13

49.90

20.30

2.77

76.37

0.56

1.1415

4.78

0.11

5.90

89.22

1.0042

0.2352

0.0389

6.0428

0.0772

3.0466

NaC

l=0.05

inInitialAqueous

Phase

1.99

2.50

45.62

49.90

3.89

4.95

90.18

0.98

1.0582

0.29

0.02

5.85

93.84

0.9776

0.0745

0.0036

20.4254

0.0648

1.1495

4.13

2.49

43.63

49.75

7.50

5.05

86.35

1.10

1.0814

1.16

0.05

6.08

92.71

0.9823

0.1548

0.0108

14.3216

0.0704

2.1995

5.88

2.50

41.73

49.90

10.53

5.21

83.29

0.98

1.1013

1.89

0.07

6.09

91.94

0.9890

0.1796

0.0139

12.9438

0.0731

2.4559

7.78

2.50

39.82

49.90

13.68

5.14

80.69

0.49

1.1196

2.90

0.10

5.96

91.03

0.9928

0.2119

0.0204

10.3946

0.0739

2.8670

9.76

2.49

37.90

49.85

16.67

5.74

77.41

0.18

1.1424

4.15

0.16

5.96

89.73

1.0006

0.2491

0.0279

8.9396

0.0770

3.2364

11.75

2.49

35.91

49.85

19.71

5.85

73.96

0.48

1.1623

5.38

0.21

5.73

88.68

1.0076

0.2729

0.0363

7.5222

0.0774

3.5240

NaC

l=0.08

inInitialAqueous

Phase

1.99

3.79

44.38

49.85

3.76

7.89

86.83

1.52

1.0822

0.33

0.04

4.87

94.77

0.9757

0.0872

0.0048

18.0132

0.0561

1.5553

3.89

3.79

42.42

49.90

7.00

7.90

84.07

1.03

1.1019

1.09

0.06

4.86

93.99

0.9806

0.1556

0.0081

19.2691

0.0577

2.6951

5.87

3.79

40.49

49.85

10.31

7.65

80.45

1.59

1.1210

1.94

0.10

5.18

92.77

0.9914

0.1880

0.0137

13.7572

0.0644

2.9174

7.78

3.79

38.52

49.90

13.03

7.74

77.66

1.57

1.1428

3.21

0.16

5.31

91.31

0.9959

0.2465

0.0210

11.7524

0.0684

3.6023

9.76

3.79

36.60

49.85

16.09

8.14

74.29

1.49

1.1613

4.57

0.23

5.81

89.38

1.0058

0.2844

0.0285

9.9774

0.0782

3.6356

11.67

3.79

34.63

49.90

19.36

7.89

71.24

1.51

1.1829

5.39

0.29

5.16

89.15

1.0096

0.2785

0.0372

7.4958

0.0725

3.8444

NaC

l=0.10

inInitialAqueous

Phase

1.99

4.99

43.12

49.90

3.72

10.48

84.19

1.60

1.1027

0.40

0.13

5.47

94.01

0.9767

0.1067

0.0120

8.9124

0.0650

1.6416

3.89

4.99

41.22

49.90

6.65

10.52

81.73

1.10

1.1203

1.45

0.18

5.44

92.93

0.9823

0.2182

0.0168

12.9688

0.0666

3.2780

5.87

4.99

39.29

49.85

9.50

10.56

79.24

0.69

1.1405

2.77

0.22

5.16

91.84

0.9893

0.2921

0.0208

14.0233

0.0652

4.4832

7.78

4.99

37.33

49.90

12.30

11.47

75.56

0.67

1.1608

3.97

0.29

5.23

90.51

0.9980

0.3229

0.0253

12.7843

0.0692

4.6636

9.77

4.99

35.34

49.90

14.88

11.46

72.70

0.96

1.1785

5.70

0.37

5.76

88.18

1.0061

0.3831

0.0321

11.9433

0.0792

4.8384

11.89

4.98

33.39

49.75

18.21

11.65

70.09

0.04

1.2046

7.00

0.48

5.23

87.30

1.0156

0.3841

0.0409

9.3863

0.0746

5.1466

NaC

l=0.13

inInitialAqueous

Phase

1.99

6.28

41.88

49.85

3.51

13.59

81.50

1.40

1.1150

0.56

0.18

4.96

94.40

0.9774

0.1600

0.0131

12.2481

0.0609

2.6276

3.89

6.29

39.92

49.90

6.36

13.71

78.35

1.58

1.1390

1.64

0.25

5.22

92.88

0.9824

0.2576

0.0184

14.0002

0.0667

3.8644

5.87

6.28

38.00

49.85

8.92

13.87

74.89

2.33

1.1651

3.14

0.28

5.17

91.41

0.9942

0.3525

0.0202

17.4429

0.0690

5.1074

Journal of Chemical & Engineering Data Article

dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXXC

Page 4: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

∑γτ

ττ

=∑

∑+

∑−

⎛⎝⎜⎜

⎞⎠⎟⎟

G x

G x

G x

G x

G x

G xln i

j ji ji j

k ki k j

ij j

k ki kij

l li lj l

k ki k

NC

NC

NC

NC

NC

NC

(3)

Table

1.continued

initialmixtures

aqueousphase

organicphase

ρaρo

ω1

ω2

ω3

ω4

ω1

ω2

ω3

ω4

(g·mL−

1 )ω

4(g·mL−

1 )D

1D

2S 1

,2D

3S 1

,3

NaC

l=0.13

inInitialAqueous

Phase

7.86

6.28

36.01

49.85

11.60

14.67

72.35

1.38

1.1787

4.67

0.38

5.53

89.42

0.9998

0.4029

0.0257

15.6482

0.0765

5.2682

9.76

6.28

34.11

49.85

14.39

14.50

69.87

1.24

1.2009

6.02

0.46

5.57

87.94

1.0103

0.4186

0.0321

13.0558

0.0797

5.2511

11.66

6.28

32.21

49.85

16.87

14.61

66.97

1.55

1.2221

7.62

0.52

5.53

86.33

1.0194

0.4519

0.0357

12.6486

0.0825

5.4754

NaC

l=0.15

inInitialAqueous

Phase

1.99

7.49

40.63

49.90

3.34

16.17

78.75

1.73

1.1385

0.71

0.67

4.71

93.91

0.9787

0.2114

0.0417

5.0738

0.0598

3.5341

3.89

7.49

38.72

49.90

5.90

16.09

76.23

1.77

1.1555

2.04

0.29

4.74

92.93

0.9871

0.3460

0.0182

19.0106

0.0622

5.5651

5.88

7.49

36.74

49.90

8.44

16.38

73.28

1.90

1.1748

3.60

0.24

4.90

91.26

0.9964

0.4263

0.0147

29.0358

0.0669

6.3724

7.78

7.49

34.83

49.90

11.07

16.78

71.08

1.07

1.1953

5.06

0.17

4.93

89.83

1.0058

0.4572

0.0103

44.1695

0.0694

6.5860

9.76

7.48

32.91

49.85

13.32

17.36

67.89

1.43

1.2170

6.86

0.41

4.93

87.79

1.0162

0.5151

0.0238

21.6428

0.0727

7.0889

11.67

7.49

30.94

49.90

15.68

18.13

64.00

2.19

1.2400

8.24

0.91

4.64

86.22

1.0210

0.5253

0.0501

10.4866

0.0725

7.2481

aThe

standard

uncertaintyforu(ω)=0.01,u(T

)=0.05

Kandu(ρ)

=0.0001

g·mL−

1 .Figure 1. Distribution coefficient of phosphoric acid (D1) as a functionof phosphoric acid composition in the initial aqueous phase at 298.15K: ■, ω = 0 NaCl; □, ω = 0.03 NaCl; ●, ω = 0.05 NaCl; ○, ω = 0.08NaCl; ▲, ω = 0.10 NaCl; △, ω = 0.13 NaCl; ▼, ω = 0.15 NaCl.

Figure 2. Separation factor of sodium chloride (S1,2) as a function ofphosphoric acid composition in the initial aqueous phase at 298.15 K:□, ω = 0.03 NaCl; ●, ω = 0.05 NaCl; ○, ω = 0.08 NaCl; ▲, ω = 0.10NaCl; △, ω = 0.13 NaCl; ▼, ω = 0.15 NaCl.

Journal of Chemical & Engineering Data Article

dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXXD

Page 5: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

τ = − =g g RT g g( )/ , ( )ji ji ii ji ij (4)

α τ α α= − =G exp( ), ( )ji ji ji ij ji (5)

τ τ= = 0ii jj (6)

= =G G 1ii jj (7)

− =g g B( )ji ii ij (8)

In eq 3, NC stands for the number of material, i stands for thecomponent (i = 1 for phosphoric acid, i = 2 for sodiumchloride, i = 3 for water).The interaction parameter for the NRTL model, in the

present work, the value of the nonrandomness is fixed at α =0.3, Bij is regressed using the firstOpt software. The regressedNRTL parameters of the quaternary system are shown in Table2 with the root-mean-square error (RMSE) values. The RMSEvalues are a measure of the agreement between the calculatedand the experimental data.

= Σ −N

x xRMSE1

( )i ical exp 2

(9)

In eq 6, N is the number of experimental data points. TheRMSE values for the experiments are < 0.01 when theexperimental data are regressed with the NRTL model.

4. CONCLUSIONSLiquid−liquid equilibrium data for the (H3PO4−NaCl−H2O−TBP) quaternary systems were obtained at T = (298.15) K andatmosphere pressure. With increasing content of phosphoricacid and sodium chloride, the distribution coefficient ofphosphoric acid increases. That is to say, the content ofphosphoric acid complexing with TBP is gradually increased.The separation factor of water increases with the increasecontents of phosphoric acid and sodium chloride, while theseparation factor of sodium chloride decreases after an increaseto a maximum value. The NRTL (α = 0.3) thermodynamicmodel is acceptably used to correlate the experimental liquid−liquid equilibrium data. It indicates that the model gives goodresult for the investigated system.

■ AUTHOR INFORMATION

Corresponding Author*E-mail: [email protected]. Tel.: (0086 0951) 3951036.Fax: (0086 0951) 3951036. Address: Department of Chemistryand Chemical Engineering, Ningxia University, No.539,Helanshan Road, Xixia District, Yinchuan, 750021, PR China.

NotesThe authors declare no competing financial interest.

■ NOMENCLATURE

Bij, coefficient as defined in eq 8; D1, distribution coefficient ofphosphoric acid; Di, distribution coefficient of material i; Di

a,distribution coefficient of material i in the aqueous phase; Di

o,distribution coefficient of material i in the organic phase; gij,energies of interaction between an i−j pair of molecules; Gij,coefficient as defined in eq 5; N, number of tie-lines; NC,number of molecules; R, gas constant; RMSE, root-mean-square error; T, absolute temperature; xi, overall mole fractionof substance i; xi

cal, calculated mole fraction; xiexp, experimental

mole fraction

Greek Lettersαij, nonrandomness constant for binary ij interaction; γ, activitycoefficient; τji, coefficient as defined in eq 4

Subscripti, component i

Figure 3. Separation factor of water (S1,3) as a function of phosphoricacid composition in the initial aqueous phase at 298.15K: ■, ω = 0NaCl; □, ω = 0.03 NaCl; ●, ω = 0.05 NaCl; ○, ω = 0.08 NaCl; ▲, ω= 0.10 NaCl; △, ω = 0.13 NaCl; ▼, ω = 0.15 NaCl.

Table 2. Quaternary System in the Different SodiumChloride Concentrations of Binary Interaction Parametersof the NRTL Equation

i j Bij Bji 108 RMSE

NaCl = 0.0 in the Initial Aqueous Phase1 2 171.41 512.96 0.0011 3 406.24 0.00242 3 −1046.27 252.63

NaCl = 0.03 in the Initial Aqueous Phase1 2 87.77 386.98 2.851 3 91.26 −53.842 3 −328.22 164.55

NaCl = 0.05 in the Initial Aqueous Phase1 2 −141.72 386.68 12.51 3 96.78 −2.902 3 1020.66 10.79

NaCl = 0.08 in the Initial Aqueous Phase1 2 100.76 17.71 0.131 3 300.72 −1.142 3 262.33 −106.33

NaCl = 0.10 in the Initial Aqueous Phase1 2 −108.14 274.05 8.911 3 −313.12 35.302 3 29.61 −0.79

NaCl = 0.13 in the Initial Aqueous Phase1 2 9.69 208.78 7.511 3 −152.87 193.192 3 675.52 0.56

NaCl = 0.15 in the Initial Aqueous Phase1 2 −76.47 155.82 2.551 3 119.10 −10.562 3 986.12 −0.024

Journal of Chemical & Engineering Data Article

dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXXE

Page 6: Liquid–Liquid Equilibria for the Quaternary System H               3               PO               4               –NaCl–H               2               O–TBP at 298.15 K

■ REFERENCES(1) Awwad N. S.; El-Nadi Y. A.; Hamed M. M. Successive processesfor purification and extraction of phosphoric acid produced by wetprocess. Chem. Eng. Process., Process Intensif.. doi.10.1016/j.cep.2012.11.009(2) Huang, H. M.; Song, Q. W.; Wang, W. J.; Wu, S. W.; Dai, J. K.Treatment of anaerobic digester effluents of nylon wastewater throughchemical precipitation and a sequencing batch reactor process. J.Environ. Manage. 2012, 101, 68−74.(3) Lian, P. C.; Meng, W. J.; Tang, D. Y. Removing magnesium inwet-process phosphoric acid solution by ion exchange technique. J.Guizhou Univ. Tech. 2008, 37, 36−39.(4) Ma, Y. The basic study of phosphoric acid crystallizationpurifying process. Thesis, East China University of Science andTechnology, 2010.(5) Amin, M. I.; Ali, M. M.; Kamal, H. M.; Youssef, A. M.; Aki, M. A.Recovery of high grade phosphoric acid from wet process acid bysolvent extraction with aliphatic alcohols. Hydrometallurgy 2010, 105,115−119.(6) Ghanadzadeh Gilani, H.; Ghanadzadeh Gilani, A.; Shekarsaraee,S. Experimental study of phase equilibria in aqueous mixtures ofphosphoric acid with isoamyl acetate and methyl isoamyl ketone at T= (298.2, 308.2, and 318.2)K. Fluid Phase Equilib. 2013, 337, 32−38.(7) Ghanadzadeh Gilani, H.; Ghanadzadeh Gilani, A.; Shekarsaraee,S.; Uslu, H. (Liquid+liquid) equilibrium data of (water+phosphoricacid+solvents) systems at T = (308.2 and 318.2) K. J. Chem.Thermodyn. 2012, 53, 52−59.(8) Ziat, K.; Messnaoui, B.; Bounahmidi, T.; de la Guardia, M.;Garrigues, S. Liquid−liquid equilibria in the system H3PO4-KCl-H2O-tri-n-butyl phosphate: Experiments and modeling. Fluid Phase Equilib.2004, 224, 39−46.(9) Xu, G. X. Chemical Theory of Extraction; Chemical Industry Press:Beijing, 1984; pp 56−86.(10) Zou, H. T. Discussion on Quimociac reagent solution fordetermination of P2O5. Phosphate Compound Fertilizer 2000, 15 (4),58−60.(11) Zhu, T.; Li, C. M. Determination of the content of chloride ionin fertilizer material by Volhard method. Chem. Fertilizer Ind. 2002, 1(29), 23−26.(12) Qiu, Y. H. Several problems during the use of Karl Fischermoisture meter. Shanghai Measure. Test. 2004, 2, 28−29.(13) Wang, C.; Xu, M. Z.; Wang, L. X.; Zou, W. B.; Hu, C. Q.; Wu,G. C. Several Karl Fischer water determination methods. Chin. J.Pharm. Anal. 2008, 28, 2145−2148.(14) Jia, X.; Li, J.; Jin, Y.; Luo, J.; Wang, B.; Qi, Y. Liquid−liquidequilibrium in the nitric acid/phosphoric acid/water/tri-n-octylaminesystem. J. Chem. Eng. Data 2012, 58 (1), 78−83.(15) Ellison, S. L. R. Quantifying Uncertainty in Analytical Measure-ment: EURACHEM-CITAC Guide; EURACHEM: 2000.(16) Eum, K. W.; Gu, H.; Lee, T. G.; Choe, J.; Lee, K.; Song, K. H.Liquid−liquid equilibria for the ternary system of perfluorohexane +methyl nonafluorobutyl ether + toluene, + 1,4-dioxane, or +dimethylformamide at 298.15 K. J. Chem. Eng. Data 2013, 58, 915−919.(17) Marcus, Y.; Kertes, A. Ion Exchange and Solvent Extraction ofMetal Complexes; Wiley: London, 1969.(18) Jin, Y.; Li, J.; Luo, J. H.; Zheng, D. S.; Liu, L. Liquid−liquidequilibrium in the system phosphoric acid/water/tri-n-butyl phos-phate/calcium chloride. J. Chem. Eng. Data 2010, 55, 3196−3199.(19) Renon, H.; Prausnitz, J. M. Local compositions inthermodynamic excess functions for liquid mixtures. AIChE J. 1968,14 (1), 135−144.

Journal of Chemical & Engineering Data Article

dx.doi.org/10.1021/je400817m | J. Chem. Eng. Data XXXX, XXX, XXX−XXXF