Phase Diagrams and Physicochemical Properties for the Ternary System

Article pubs.acs.org/jced

Phase Diagrams and Physicochemical Properties for the Ternary System (CsCl + NaCl + H2O) at T = (298.15, 308.15, and 318.15) K Yunxue Gao, Shuni Li,* Quanguo Zhai, Yucheng Jiang, and Mancheng Hu* Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710062, P. R. China ABSTRACT: Complete phase diagrams and physico-chemical properties for the ternary system (CsCl + NaCl + H2O) were determined at T = (298.15, 308.15, and 318.15) K, respectively. The X-ray diffraction method and Schreinemaker’s wet residue method were used to verify the solid phase. The phase diagrams show this ternary system is a complex type. Three crystallization regions were found corresponding to the single salt NaCl, a compound CsCl·2NaCl·2H2O, and a solid solution series [Cs1−x(Na·H2O)x]Cl (x in [Cs1−x(Na·H2O)x]Cl changed from 0 to 0.43 (298.15 K), 0.39 (308.15 K), and 0.36 (318.15 K) at each temperature. With rising temperature, the crystallization area of NaCl increased, but CsCl·2NaCl·2H2O and [Cs1−x(Na·H2O)x]Cl decreased simultaneously. However, density and refractive index increased with increasing CsCl concentration.

1. INTRODUCTION

In recent years, our research group has conducted continuing research on the phase behavior of rare alkali metal (Rb and Cs) salts in different systems, such as water + 1-propanol + KCl + CsCl16 and water + 1−propanol + Cs2SO4 + CsCl.17 Although Chou et al.18−20 investigated the ternary system (NaCl + CsCl + H2O) at different temperatures, only the results in CsCl-rich region were given. Therefore, in this work, the phase behavior in the whole concentration ranges for both CsCl and NaCl in

The salt lakes in China and all over the world contain abundant inorganic salt resources, such as Na+, K+, Mg2+, Li+, Rb+, and Cs+, etc. However, the coexistence of the salts has greatly influenced the application of such resources.1,2 Data of solubility in water−salt systems supply a very important foundation for the separation and purification progress. So the investigation of phase equilibria plays an important role in the process of the rational use of salt resources and industrial applications.3−6 For example, Li+ always coexists with Mg2+, so the lithium resource separation process is according to the solubility phenomenon.7,8 Similarly, industrial KH2PO4 can be prepared by an ion exchange method, direct chemical conversion method, crystallization method, and solvent extraction method with KCl based on phase equilibria.9,10 However, new compounds and a solid-solution were often formed in the mixed electrolyte systems contain Cs+. For example, Jendoubi et al.11 studied the mixing enthalpies in the solid-solution (Cs1−x,Rbx)NO3 at temperatures from 298.15 to 473.15 K. Yariv et al.12 found that the new salt Cs[Na(H2O)]2Br3 and solid-solution Cs1−x[Na(H2O)]xBr (x ≤ 0.48) were formed in the ternary system (NaBr + CsBr + H2O) at 298.15 K. However, when HCl was added as a solvent in the system CsCl + TbCl3 + HCl (∼7.6 mass %) at 298.2 K,13 two new compounds Cs5TbCl8·6H2O and Cs2TbCl5·6H2O were found in the system. In the similar systems, such as CsCl + LuCl3 + HCl (10.06%) + H2O and CsCl + YbCl3 + HCl (11.3%) + H2O at 298.15 K,14,15 similar new compounds were also formed as Cs4LuCl7·5H2O, Cs9Lu5Cl24·29H2O, Cs2LuCl5·2H2O, and Cs4YbCl7·4H2O, Cs2YbCl5·5H2O. Therefore, for electrolyte systems containing Cs+, more research should be done to obtain new information on phase behavior of the salts. © 2017 American Chemical Society

Table 1. Purities and Suppliers of Chemicals mass fraction purity

chemical

source

sodium chloride cesium chloride silver nitrate potassium chromate sodium tetraphenylboron hydrochloric acid sulfuric acid acetic acid methyl red

Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Aladdin Industrial rporation

≥0.995 ≥0.995 ≥0.998 ≥0.995 ≥0.995

Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Sinopharm Chemical Reagent Co., Ltd. Tianjin Tianxin Fine Chemical Development Center

0.36−0.38 0.95−0.95 ≥0.995 AR

the ternary system (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K was conducted. Moreover, the density and refractive index of the system were determined to get more information on such a system. Special Issue: Memorial Issue in Honor of Ken Marsh Received: January 10, 2017 Accepted: March 15, 2017 Published: March 27, 2017 2533

DOI: 10.1021/acs.jced.7b00023 J. Chem. Eng. Data 2017, 62, 2533−2540

Journal of Chemical & Engineering Data

Article

Table 2. Comparison of the Solubility, Density, and Refractive Index of NaCl and CsCl Saturated Aqueous Solutions with Literature Values at T = (298.15, 308.15, and 318.15) K and p = 101.3 kPaa T = 298.15 this work reference this work reference this work reference

100w ρ/(g·cm−3) nD

T = 308.15

T = 318.15

CsCl

NaCl

CsCl

NaCl

CsCl

NaCl

65.38 65.64,30 65.7531 1.9239 1.922133 1.4196 1.419733

26.30 26.45,30 26.4532 1.1978 1.1982,33 1.197834 1.3796 1.3800,33 1.379534

66.93 66.9331 1.9461 1.947533 1.4204 1.420433

26.66 26.5932 1.1936 1.193033 1.3781 1.377933

67.88 68.1431 1.9808 1.984433 1.4218 1.421133

26.69 26.5932 1.1889 1.189633 1.3766 1.376433

Standard uncertainties u are u(T) = 0.1 K, u(w(NaCl)) = 0.005 (mass fraction), u(w(CsCl)) = 0.005 (mass fraction), u(ρ) = 0.0015 g·cm−3, u(nD) = 0.001, u(P) = 10 kPa.

a

Table 3. Solid−Liquid Equilibrium, Refractive Index, and Density of the Ternary System (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K and p = 101.3 kPa composition of liquid phase, 100wa

composition of wet residue, 100wa

properties of liquid phasea

H2O

ρ/(g·cm−3)

nD

equibrium solid phasec

ND 18.21 18.00 16.94 17.16 16.10 16.94 16.55 14.44 15.76 6.83 2.99 2.76 1.54 1.92 0.99 0.51 ND

1.1978 1.2308 1.2631 1.3105 1.3848 1.4577 1.4981 1.5474 1.5970 1.6417 1.6552 1.7274 1.7741 1.8015 1.8297 1.8590 1.8855 1.9239

1.3796 1.3816 1.3837 1.3874 1.3915 1.3962 1.3994 1.4024 1.4056 1.4081 1.4082 1.4122 1.4141 1.4153 1.4161 1.4178 1.4184 1.4196

N N N N N N N N N N+H T+H T T T T T T S

ND 18.65 18.84 19.30 17.61 19.07 19.49 18.43 14.88 15.96 17.00 6.01 3.68 2.93 1.24 1.86 0.04 ND

1.1936 1.2279 1.2585 1.3202 1.3757 1.4035 1.4784 1.5423 1.5885 1.6556 1.6841 1.6952 1.7432 1.7677 1.7985 1.8481 1.9165 1.9461

1.3781 1.3802 1.3822 1.3861 1.3899 1.3916 1.3967 1.4009 1.4041 1.4069 1.4100 1.4102 1.4130 1.4140 1.4153 1.4174 1.4197 1.4204

N N N N N N N N N N N+H T+H T T T T T S

ND 17.60 16.57 16.36 17.55 17.52

1.1889 1.2226 1.2444 1.3001 1.3918 1.4867

1.3766 1.3788 1.3807 1.3835 1.3899 1.3963

N N N N N N

no.

CsCl

NaCl

H2O

CsCl

1(A1) 2 3 4 5 6 7 8 9 10(C1) 11(C2) 12 13 14 15 16 17 18(B1)

0.00 4.33 8.34 12.70 19.51 25.79 29.64 33.75 38.59 42.19 43.43 48.28 52.85 55.75 56.99 60.05 61.78 65.38

26.30 24.81 23.38 21.81 19.26 17.35 16.20 14.79 12.75 11.61 10.54 8.50 6.55 4.93 4.28 2.90 2.08 0.00

73.70 70.86 68.28 65.49 61.23 56.86 54.16 51.46 48.66 46.20 46.03 43.22 40.60 39.32 38.73 37.05 36.14 34.62

NDb 0.75 2.22 4.13 4.97 7.92 8.34 9.80 10.22 18.79 74.53 85.68 89.03 92.45 93.37 96.76 98.15 ND

1(A2) 2 3 4 5 6 7 8 9 10 11(C3) 12(C4) 13 14 15 16 17 18(B2)

0.00 4.54 8.11 13.78 19.19 21.17 27.01 33.27 38.36 42.78 44.95 46.22 50.31 53.56 55.93 58.68 64.59 66.93

26.66 25.00 23.65 21.36 19.75 19.02 17.33 15.03 13.24 11.50 10.99 10.25 8.54 7.04 5.77 4.48 1.52 0.00

73.34 70.46 68.24 64.86 61.06 59.81 55.66 51.70 48.40 45.72 44.06 43.53 41.15 39.40 38.30 36.84 33.89 33.07

ND 0.73 2.00 3.65 5.96 7.22 8.90 10.79 12.25 14.75 25.20 77.45 85.01 87.64 91.04 94.09 99.08 ND

1(A3) 2 3 4 5 6

0.00 4.48 7.21 12.80 20.16 27.55

26.69 24.97 24.00 21.89 19.38 17.04

73.31 70.55 68.79 65.31 60.46 55.41

ND 0.67 2.28 3.69 4.87 7.69

NaCl 298.15 K ND 81.04 79.78 78.93 77.87 75.98 74.72 73.65 75.34 70.45 18.64 11.33 8.21 6.01 4.71 2.25 1.34 ND 308.15 K ND 80.62 79.16 77.05 76.43 73.71 71.61 70.78 72.87 69.29 65.51 16.54 11.31 9.43 7.72 4.05 0.88 ND 318.15 K ND 81.73 81.15 79.95 77.58 74.79 2534



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Table 3. continued composition of liquid phase, 100wa

composition of wet residue, 100wa

properties of liquid phasea

H2O

ρ/(g·cm−3)

nD

equibrium solid phasec

13.96 16.08 13.12 11.11 5.38 4.10 2.73 1.71 0.87 0.98 ND

1.5568 1.6234 1.6941 1.7406 1.7502 1.7625 1.8047 1.8501 1.9027 1.9381 1.9808

1.4008 1.4044 1.4097 1.4130 1.4132 1.4146 1.4158 1.4181 1.4199 1.4212 1.4218

N N N N+H T+H T T T T T S

no.

CsCl

NaCl

H2O

CsCl

NaCl

7 8 9 10(C5) 11(C6) 12 13 14 15 16 17(B3)

33.78 39.63 45.06 48.98 49.99 51.33 54.53 58.49 61.88 64.58 67.88

14.89 12.75 11.00 9.85 9.45 8.96 7.33 5.25 3.65 2.14 0.00

51.33 47.62 43.94 41.17 40.56 39.71 38.14 36.26 34.47 33.28 32.12

8.68 11.10 11.89 27.75 79.41 83.86 86.22 92.54 96.56 98.03 ND

318.15 K 77.36 72.82 74.99 61.14 15.21 12.04 11.05 5.75 2.57 0.99 ND

Standard uncertainties u are u(T) = 0.1 K, u(w(NaCl)) = 0.005 (mass fraction), u(w(CsCl)) = 0.005 (mass fraction), u(ρ) = 0.0015 g·cm−3, u(nD) = 0.001, u(P) = 10 kPa. bND, not determined. cN, NaCl, S, CsCl, H, CsCl·2NaCl·2H2O, T, solid-solution [Cs1−x(Na·H2O)x]Cl.

a

Figure 1. Phase diagram for the ternary system (CsCl + NaCl + H2O) at T = (a) 298.15, (b) 308.15, and (c) 318.15 K: ●, equilibrium liquid phase composition; □, wet solid phase; 100w1, mass fraction of CsCl; 100w2, mass fraction of NaCl; W, H2O; N, pure solid of NaCl; S, pure solid of CsCl; H, CsCl·2NaCl·2H2O; T1, T2, T3, solid-solution [Cs1−x(Na·H2O)x]Cl; A1, A2, A3, solubility of NaCl in water; B1, B2, B3, solubility of CsCl in water; C1−C6, invariant points. 2535



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Figure 2. Phase diagram for the ternary system (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K: ▲, 298.15 K; ■, 308.15 K; ●, 308.15 K; 100w1, mass fraction of CsCl; 100w2, mass fraction of NaCl; W, H2O; N, pure solid of NaCl; S, pure solid of CsCl; H, CsCl·2NaCl· 2H2O; T, solid-solution [Cs1−x, (Na·H2O)x]Cl.

Figure 4. (a) Refractive index and (b) density vs w(CsCl) in the ternary system (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K: ▲, 298.15 K; ■, 308.15 K; ●, 308.15 K.

Table 4. Refractive Index (n0), Density (d0) of Pure Water and Constants for Calculation of Refractive Index and Density in the Ternary System (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K and p = 101.3 kPa T/K

constant

NaCl

CsCl

n0

d0/g·cm−3

298.15

Ai Bi Ai Bi Ai Bi

0.0013208 0.0069747 0.0012963 0.0068639 0.0012946 0.0068520

0.0009685 0.0100532 0.0009679 0.0100369 0.0009846 0.0102142

1.33250

0.99704

1.33130

0.99403

1.32985

0.99021

308.15

Figure 3. Comparison of solubility data for the ternary system (CsCl + NaCl + H2O) at T = 298.15 K. ●, this work; ○, ref 19.

318.15

2. EXPERIMENTAL SECTION 2.1. Materials and Apparatus. Ultrapure water with electrical resistivity under 18.25 MΩ·cm−1 was used for preparing samples. The materials used in this work are shown in Table 1. CsCl and NaCl are dried to constant weight at T = 393.15 K. The phase equilibrium was attained by a semi-microphase equilibrium installation.21−23 The density (d) and refractive index (nD) were determined by a DMA 4500 (Anton Paar) vibrating tube densimeter and RXA 170 (Anton Paar) refractometer. 2.2. Experimental Methods. The isothermal solution saturation method24,25 was used for solubility determination in this work. All the samples were prepared by adding the second salt with a certain quality after getting the binary saturation system at the experimental temperature. The supernatant was taken regularly for analysis until compositions of the liquid

phase were constant, which denotes the equilibrium of the system. According to experimental results, it took about 24 h to obtain equilibrium and another 6 h to isolate the wet residue from the liquid phase. Then the liquid samples were taken for quantitative analysis and for measurement of the refractive index and density. Meanwhile, the solid phase was analyzed by the Schreinemaker’s wet residue method,26,27 and X-ray diffraction (XRD; D/Max2550VB+/PC; Rigaku Corporation). All X-ray diffraction analyses were recorded at 40 kV and 100 mA using Cu Kα (λ = 1.54056 Å) with a scan speed of 0.15 s/step and a step size of 0.02°. 2.3. Composition Analysis Method. The composition of the liquid phase and the solid phase were measured by the method of chemical analysis. The concentration of Cl− was analyzed by Mohr’s method.28 The concentration of Cs+ was 2536



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Table 5. Comparison of the Calculated (calcd) and Experimental (expt) Values of Density and Refractive Index in the Ternary System (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K and p = 101.3 kPa density ρ/g·cm−3 a

no.

expt

calcd

1(A1) 2 3 4 5 6 7 8 9 10(C1) 11(C2) 12 13 14 15 16 17 18(B1)

1.1978 1.2308 1.2631 1.3105 1.3848 1.4577 1.4981 1.5474 1.5970 1.6417 1.6552 1.7274 1.7741 1.8015 1.8297 1.8590 1.8855 1.9239

1.1978 1.2382 1.2736 1.3190 1.3856 1.4564 1.4996 1.5519 1.6062 1.6523 1.6606 1.7189 1.7754 1.8074 1.8218 1.8607 1.8826 1.9239

1(A2) 2 3 4 5 6 7 8 9 10 11(C3) 12(C4) 13 14 15 16 17 18(B2)

1.1936 1.2279 1.2585 1.3202 1.3757 1.4035 1.4784 1.5423 1.5885 1.6556 1.6841 1.6952 1.7432 1.7677 1.7985 1.8481 1.9165 1.9461

1.1936 1.2351 1.2684 1.3217 1.3801 1.4008 1.4683 1.5390 1.5998 1.6526 1.6832 1.6960 1.7464 1.7859 1.8131 1.8472 1.9208 1.9461

1(A3) 2 3 4 5 6 7 8 9 10(C5) 11(C6) 12 13 14 15 16 17(B3)

1.1889 1.2226 1.2444 1.3001 1.3918 1.4867 1.5568 1.6234 1.6941 1.7406 1.7502 1.7625 1.8047 1.8501 1.9027 1.9381 1.9808

1.1889 1.2300 1.2564 1.3112 1.3895 1.4745 1.5483 1.6188 1.6917 1.7471 1.7603 1.7787 1.8173 1.8656 1.9101 1.9434 1.9808

refractive index nD relative errorb 298.15 K 0.0000 0.0060 0.0083 0.0065 0.0006 −0.0009 0.0010 0.0029 0.0058 0.0065 0.0033 −0.0049 0.0007 0.0033 −0.0043 0.0009 −0.0015 0.0000 308.15 K 0.0000 0.0059 0.0079 0.0011 0.0032 −0.0019 −0.0068 −0.0021 0.0071 −0.0018 −0.0005 0.0005 0.0018 0.0103 0.0081 −0.0005 0.0022 0.0000 318.15 K 0.0000 0.0061 0.0096 0.0085 −0.0017 −0.0082 −0.0055 −0.0028 −0.0014 0.0037 0.0058 0.0092 0.0070 0.0084 0.0039 0.0027 0.0000

expta

calcd

relative errorb

1.3796 1.3816 1.3837 1.3874 1.3915 1.3962 1.3994 1.4024 1.4056 1.4081 1.4082 1.4122 1.4141 1.4153 1.4161 1.4178 1.4184 1.4196

1.3796 1.3827 1.3854 1.3884 1.3929 1.3979 1.4010 1.4039 1.4067 1.4095 1.4092 1.4120 1.4147 1.4156 1.4161 1.4177 1.4185 1.4196

0.0000 0.0008 0.0012 0.0007 0.0010 0.0012 0.0011 0.0011 0.0008 0.0010 0.0007 −0.0001 0.0004 0.0002 0.0000 −0.0001 0.0001 0.0000

1.3781 1.3802 1.3822 1.3861 1.3899 1.3916 1.3967 1.4009 1.4041 1.4069 1.4100 1.4102 1.4130 1.4140 1.4153 1.4174 1.4197 1.4204

1.3781 1.3812 1.3836 1.3871 1.3914 1.3928 1.3976 1.4019 1.4056 1.4084 1.4105 1.4108 1.4133 1.4150 1.4159 1.4173 1.4200 1.4204

0.0000 0.0007 0.0010 0.0007 0.0011 0.0009 0.0006 0.0007 0.0011 0.0011 0.0004 0.0004 0.0002 0.0007 0.0004 −0.0001 0.0002 0.0000

1.3766 1.3788 1.3807 1.3835 1.3899 1.3963 1.4008 1.4044 1.4097 1.4130 1.4132 1.4146 1.4158 1.4181 1.4199 1.4212 1.4218

1.3766 1.3796 1.3816 1.3854 1.3910 1.3969 1.4016 1.4058 1.4101 1.4135 1.4142 1.4151 1.4166 1.4183 1.4201 1.4211 1.4218

0.0000 0.0006 0.0007 0.0014 0.0008 0.0004 0.0006 0.0010 0.0003 0.0004 0.0007 0.0004 0.0006 0.0001 0.0001 −0.0001 0.0000

Standard uncertainties u are u(T) = 0.1 K, u(w(NaCl)) = 0.005 (mass fraction), u(w(CsCl)) = 0.005 (mass fraction), u(ρ) = 0.0015 g·cm−3, u(nD) = 0.001, u(P) = 10 kPa. bRelative error = (calculated value − experimental value)/experimental value.

a

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in Figure 4. The density and refractive index at the three temperatures all increase with increasing CsCl concentration. The empirical eqs 1 and (2)36−38 were used to calculate the refractive index and density for the liquid phase in electrolyte solutions. The density and refractive index of the electrolyte solutions varied linearly with the composition of the solution. Therefore, the calculation results were usually applied to verify the experimental data and the theoretical model.

analyzed by the gravimetric methods with the precipitation of CsB(C6H5)4.29 The concentration of Na+ was calculated according to the charge balance of ions. Every result was an average value determined by three parallel experiments.

3. RESULTS AND DISCUSSION 3.1. Solubility Data for the Ternary System (CsCl + NaCl + H2O). The solubility, density, and refractive index of CsCl and NaCl saturated aqueous solutions in this work were compared with values in the literature30−34 as listed in Table 2. The results showed good agreement. The experimental solubilities of the ternary system (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K are presented in Table 3. The concentrations both in the solutions and the solid phase are shown as mass fractions. According to the experimental data in Table 3, the stable equilibrium phase diagrams at T = (298.15, 308.15, and 318.15) K are plotted in Figure 1panels a, b, and c, respectively. The ternary system (CsCl + NaCl + H2O) at T = (298.15, 308.15 and 318.15) K all have two invariant points and three crystallization regions, which correspond to the single salt NaCl, compound CsCl·2NaCl·2H2O and a solid-solution series [Cs1−x(Na·H2O)x]Cl with x ranging from 0 to 0.43 (298.15 K), 0 to 0.39 (308.15 K) and 0 to 0.36 (318.15 K). The maximum values of x were calculated by the boundary samples with constant composition of [Cs1−x(Na·H2O)x]Cl. The structure of compound CsCl·2NaCl·2H2O was determined according to Evans et al.35 In Figure 1a, points N, S, and W represent the pure NaCl, pure CsCl, and H2O. Points A1 and B1 represent the solubilities of single salt NaCl and CsCl with mass fraction corresponding to w(NaCl) = 26.30% (A1) and w(CsCl) = 65.38% (B1) at T = 298.15 K. Points C1 and C2 are the invariant points. The composition of C1 are w(NaCl) = 11.61% and w(CsCl) = 42.19%, corresponding the solid NaCl + CsCl·2NaCl·2H2O. The composition of C2 are w(NaCl) = 10.54% and w(CsCl) = 43.43%, corresponding to the solid CsCl·2NaCl·2H2O + solidsolution [Cs1−x(Na·H2O)x]Cl (x = 0.43). The regions A1C1N, C1C2H, and B1C2T1S are crystallization regions of NaCl, CsCl· 2NaCl·2H2O, and a solid-solution series [Cs1−x(Na·H2O)x]Cl (x = 0 to 0.43). Other regions of the phase diagram include C1NH, C2HT1, and NHT1S which are crystallization regions of NaCl + CsCl·2NaCl·2H2O, CsCl·2NaCl·2H2O + [Cs1−x(Na· H2O)x]Cl, and NaCl + CsCl. Figure 1 panels b and c show that the phase diagrams of the ternary system (CsCl + NaCl + H2O) at T = 308.15 and 318.15 K are similar to that of 298.15 K. A comparison of the solubility for the ternary system (CsCl + NaCl + H2O) at three temperatures was shown in Figure 2. It can be seen that the crystallization regions of NaCl from A1C1N to A3C5N increase with rising temperature. However, the crystallization regions of CsCl·2NaCl·2H2O from C1C2H to C5C6H decrease with the temperature changing from T = 298.15 to 318.15 K, and disappears at T = 323.15 K.20 The crystallization regions of [Cs1−x(Na·H2O)x]Cl also decrease with x changed from 0.43 to 0.36. Figure 3 is the comparison of ternary system (CsCl + NaCl + H2O) at T = 298.15 K in this work and the literature.19 Points LC1 and LC2 represent the invariant points of the CsCl-rich region in the literature. It can be seen that the data from this work is in high agreement with the values in the literature. 3.2. Physico-chemical Properties Comparison between Experimental and Calculation Data. Density and refractive index of the saturation solution are listed in Table 3 and plotted

ln(n/n0) =

∑ (A i × wi)

(1)

ln(d /d0) =

∑ (Bi × wi)

(2)

where n, d, and n0, d0 refer to the refractive index and density of the equilibrium liquid phase and pure water at T = (298.15, 308.15 and 318.15) K. wi represents the mass fraction of substance i in the liquid phase. Ai and Bi are the coefficients of NaCl and CsCl, which can be calculated by the saturated binary system (NaCl+H2O) and (CsCl+H2O) at each temperature. The values of n0, d0, Ai, and Bi are listed in Table 4. The calculated density and refractive index of the CsCl + NaCl + H2O system are listed in Table 5. The results from the calculations are in good agreement with the experiment data as displayed by the deviations of the comparison. 3.3. XRD Patterns for Invariant Points. Figure 5 is the X-ray diffraction pattern corresponding to the invariant points.

Figure 5. X-ray diffraction pattern of the invariant point C1, C3, and C5 at T = (298.15, 308.15, and 318.15) K.

C1, C3, and C5 were verified to be the coexistence of NaCl + CsCl·2NaCl·2H2O. Because the structural similarity of the solid-solution [Cs1−x(Na·H2O)x]Cl and CsCl·2NaCl·2H2O,19 only the compositions of C2, C4, and C6 were analyzed and the values of x in [Cs1−x(Na·H2O)x]Cl were calculated corresponding to C2, C4, and C6.

■

CONCLUSIONS In this paper, the complete phase diagrams for the ternary system (CsCl + NaCl + H2O) were obtained. Two invariant points and three crystallization regions were found in this system at T = (298.15, 308.15 and 318.15) K, respectively. The invariant points are the coexistence of NaCl + CsCl·2NaCl·2H2O and CsCl·2NaCl·2H2O + solid-solution [Cs1−x(Na·H2O)x]Cl. Three crystallization regions were NaCl, CsCl·2NaCl·2H2O, and a solid-solution series [Cs1−x(Na·H2O)x]Cl, in which the x in 2538



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(14) Qiao, Z. P.; Xie, H. Q.; Zhuo, L. H.; Chen, X. Study on Phase Equilibrium in the Quaternary System CsCl − LuCl3 − HCl (10.06%) − H2O at 298.15 ± 0.1 K and New Solid − Phase Compounds. J. Chem. Eng. Data 2007, 52, 1681−1685. (15) Qiao, Z. P.; Xie, H. Q.; Chen, X.; Wang, H. Phase Equilibrium in the CsCl + YbCl3 + HCl (11.3%) + H2O System at 298.2 K and Thermodynamic Properties of New Solid Phase Compounds. J. Chem. Eng. Data 2013, 58, 3125−3129. (16) Wang, M. X.; Hu, M. C.; Zhai, Q. G.; Li, S. N.; Jiang, Y. C.; Guo, H. Y. Equilibrium Phase Behavior for Water + 1 − Propanol + Potassium Chloride + Cesium Chloride Quaternary Systems at Different Temperatures and Data Correlation. J. Chem. Eng. Data 2008, 53, 1387−1392. (17) Hu, M. C.; Jin, L. H.; Li, S. N.; Jiang, Y. C. Quaternary Liquid − Liquid Equilibrium for Water + 1 − Propanol + Cesium Sulfate + Cesium Chloride at 298.15 K. Fluid Phase Equilib. 2006, 242, 136− 140. (18) Chou, I. − M.; Lee, R. D. Solubility Relations in the Ternary System NaCl − CsCl − H2O at 1 atm. 1. Solubilities of Halite from 293.15 to 373.15 K. J. Chem. Eng. Data 1983, 28, 390−393. (19) Chou, I. − M; Romankiw, L. A.; Evans, H. T.; Konnert, J. A. Solubility Relations in the Ternary System NaCl − CsCl − H2O at 1 atm. 2. Solubility Relations at 298.15 K. J. Chem. Eng. Data 1983, 28, 393−396. (20) Chou, I. − M.; Romankiw, L. A. Solubility Relations in the Ternary System NaCl − CsCl − H2O at 1 atm. 3. Solubility Relations at 323.15 and 348.15 K. J. Chem. Eng. Data 1983, 28, 396−398. (21) Tang, J.; Li, S. N.; Zhai, Q. G.; Jiang, Y. C.; Hu, M. C. Measurements and Correlations of the Solid − Liquid Equilibrium of RbCl/CsCl + [Cnmim]Cl (n = 2, 4, 6, 8) + H2O Ternary Systems at T = (288.15, 298.15, and 308.15) K. J. Chem. Eng. Data 2014, 59, 726− 735. (22) Zhou, Y. H.; Li, S. N.; Zhai, Q. G.; Jiang, Y. C.; Hu, M. C. Solubilities, Densities and Refractive Indices for the Ternary Systems Ethylene Glycol + MCl + H2O (M = Na, K, Rb, Cs) at (288.15 and 308.15) K. J. Chem. Thermodyn. 2010, 42, 764−772. (23) Meng, R.; Li, S. N.; Zhai, Q. G.; Jiang, Y. C.; Lei, H.; Zhang, H. Y.; Hu, M. C. Solubilities, Densities, and Refractive Indices for the Ternary Systems Glycerin + MCl + H2O (M = Na, K, Rb, Cs) at (298.15 and 308.15) K. J. Chem. Eng. Data 2011, 56, 4643−4650. (24) Sang, S. H.; Zhang, H.; Zhong, S. Y.; Hu, J. W.; Sun, M. L. Experimental Study of the Solubilities of Salts in the Systems Na2B4O7 − NaBr − H2O and Na2B4O7 − Na2SO4 − NaBr − H2O at 323 K. Fluid Phase Equilib. 2014, 361, 171−174. (25) Zhang, W.; Huang, Y.; Chen, Y.; Hughes, S. S.; Zhong, L. C.; Zou, F. Solid − Liquid Equilibrium of Quaternary System Cd2+, K+, Na+//SO42−−H2O at 298 K. Fluid Phase Equilib. 2014, 363, 55−58. (26) Schott, H. A Mathematical Extrapolation for the Method of Wet Residues. J. Chem. Eng. Data 1961, 6, 324−324. (27) Hongkun, Z.; Qiuhong, Z.; Rongrong, L.; Xianchao, M.; Haizhe, J.; Panming, J.; Qishu, Q. Solid − Liquid Phase Equilibrium and Phase Diagram for Ternary o−Nitrobenzoic Acid−p−Nitrobenzoic Acid− Acetone System at 283.15K and 313.15K. Fluid Phase Equilib. 2008, 266, 101−104. (28) Yoder, L. Adaptation of the Mohr Volumetric Method to General Determinations of Chlorine. J. Ind. Eng. Chem. 1919, 11, 755− 755. (29) Kirgintsev, A. N.; Kozitskii, V. P. Solubility of Tetraphenylborates of the Alkali Metals and Ammonium in Acetone − Water Mixtures at 298.15 K. Bull. Acad. Sci. USSR, Div. Chem. Sci. 1968, 17, 1116−1118. (30) Lide, D. R. CRC Handbook of Chemistry and Physics, 89th ed.; CRC Press: Boca Raton, FL, 2009. (31) Apelblat, A.; Korin, E. The Molar Enthalpies of Solution and Vapour Pressures of Saturated Aqueous Solutions of Some Cesium Salts. J. Chem. Thermodyn. 2006, 38, 152−157. (32) Apelblat, A.; Korin, E. The Vapour Pressures of Saturated Aqueous Solutions of Sodium Chloride, Sodium Bromide, Sodium Nitrate, Sodium Nitrite, Potassium Iodate, and Rubidium Chloride at

[Cs1−x(Na·H2O)x]Cl changed from 0 to 0.43 (298.15 K), 0 to 0.39 (308.15 K), and 0 to 0.36 (318.15 K). Density and refractive index were calculated by the empirical equations.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Shuni Li: 0000-0002-6614-9241 Quanguo Zhai: 0000-0003-1117-4017 Mancheng Hu: 0000-0003-2920-0439 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Nos. U1607116, 21571120) and the Fundamental Research Funds for the Central Universities (GK201701003).

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REFERENCES

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Phase Diagrams and Physicochemical Properties for the Ternary System

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