Measurement of Mineral Solubilities in the Quaternary Systems KCl

Mar 20, 2017 - In this work, the solubilities of the salt minerals in quaternary systems potassium chloride–magnesium chloride–zinc chloride–wat...
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Measurement of Mineral Solubilities in the Quaternary Systems KCl−MgCl2−ZnCl2−H2O and KCl−MgCl2−PbCl2−H2O at 373 K Xue-Ping Zhang,† Wei Wang,† Yu-Yan Yang,† Fu-Peng Dai,† and Shi-Hua Sang*,†,‡ †

College of Materials and Chemistry and Chemical Engineering, Chengdu University of Technology, Chengdu 610059, People’s Republic of China ‡ Mineral Resources Chemistry Key Laboratory of Sichuan Higher Education Institutions, Chengdu 610059, People’s Republic of China ABSTRACT: In this work, the solubilities of the salt minerals in quaternary systems potassium chloride−magnesium chloride−zinc chloride−water and potassium chloride−magnesium chloride−lead chloride−water were measured at 373 K using an isothermal dissolution equilibrium method. Phase diagrams were constructed based on compositions of saturated liquid phase and existing equilibrium solid phase. By X-ray powder diffraction identification, a variety of solid forms were determined for the quaternary system KCl−MgCl2−ZnCl2−H2O at 373 K. Not only were three single salts KCl, ZnCl2, and MgCl2·6H2O determined but also three double salts KCl· MgCl2·6H2O(Car), 2KCl·ZnCl2, and MgCl2·ZnCl2·5H2O were detected. It also demonstrated that five precipitates KCl, MgCl2· 6H2O, KCl·MgCl2·6H2O(Car), KCl·2PbCl2, and PbCl2 were formed in the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K. CaCl2−ZnCl2−H2O, CaCl2−PbCl2−H2O, and PbCl2−ZnCl2− H2O.12,13 Although some relevant researches have been conducted, there has been no report about these two systems at any temperature. The research aims at evaluating the mineral solubilities and identifying equilibrium solid phases in the two aqueous quaternary systems KCl−MgCl2−ZnCl2−H2O and KCl− MgCl2−PbCl2−H2O at 373 K. Those new experimental data can be useful for understanding phase equilibria and thermodynamics in systems for ore-forming geochemical processes.

1. INTRODUCTION Thermodynamic studies of electrolyte solutions are of great importance in understanding hydrothermal mineralization and hydrometallurgical processes.1 In the process of lead−zinc oreforming, sodium, potassium, magnesium, and calcium are the main elements of fluid inclusions.2 Traditionally, the solubility of the minerals was affected by alkali and alkaline earth metal chlorides such as NaCl, KCl, MgCl2, and CaCl2.3 Therefore, it is very necessary to investigate the thermodynamic properties (especially the solubilities) of the multicomponent system Pb−Zn−Na−K−Mg−Ca−Cl−H2O at 373 K. It is widely acknowledged that the solubility of the salts is used to calculate the supersaturation and determine the optimum condition for crystal growth.4 Moreover, it is necessary for the designation and operation of solvent extraction.5 Because of the economic importance of lead and zinc, studies involving the solubility of lead chloride and zinc chloride were carried out. The ternary system NaCl−ZnCl2−H2O has been investigated at different temperatures, such as 273.15,6 260.35, and 250.15 K.7 Because of the application of high density fluids in petroleum production, solubilities and densities in CaCl2− ZnCl2−H2O system at 273.15 and 298.15 K8 and CaCl2 + ZnCl2 + H2O (NaCl saturated) at T = 288.15 K9 have been measured. The solubility of ZnCl2 and CO(NH2)2 mixtures in hydrochloric acid solution at T = 298.15 K has been carried out.10 Lead solubility in aqueous chloride leach liquors containing HCl, CuCl2, and either NaCl or CaCl2 were measured.11 In the previous study, we have investigated the solubilities and densities of the ternary systems KCl−ZnCl2−H2O, © 2017 American Chemical Society

Table 1. Sample Description Table chemical reagent KCl

mole fraction purity

source

≥99.5% Chengdu Kelong Chemical Reagent Manufacture, China

MgCl2·6H2O ≥98%

Chengdu Kelong Chemical Reagent Manufacture, China

≥98%

Chengdu Kelong Chemical Reagent Manufacture, China

ZnCl2 PbCl2

≥99.5% Chengdu Kelong Chemical Reagent Manufacture, China

analysis method chemical titration method chemical titration method chemical titration method chemical titration method

Received: November 17, 2016 Accepted: March 1, 2017 Published: March 20, 2017 1403

DOI: 10.1021/acs.jced.6b00960 J. Chem. Eng. Data 2017, 62, 1403−1410

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Table 2. Solubilities of the Quaternary System KCl−MgCl2−ZnCl2−H2O at 373 K and 94.77 KPaa Jänecke index Jb (g/100g dry salt)

composition of the solution, 100·wb no.

ZnCl2

MgCl2

KCl

ZnCl2

MgCl2

KCl

H2O

solid phases

1, A 2 3, E1 4 5 6 7, E2 8 9 10 11, E3 12, B 13 14 15, C 16 17 18 19 20 21 22 23, D 24 25 26 27 28 29 30 31, F 32, E4 33 34 35 36, G 37 38 39 40 41 42

0.00 6.81 8.53 13.25 20.20 22.64 25.74 44.26 46.66 51.49 55.79 0.00 6.34 8.28 37.74 37.26 37.20 35.42 34.87 32.84 31.16 27.61 62.05 61.93 61.82 60.87 60.53 59.90 59.71 58.33 11.34 10.50 10.07 9.59 9.08 62.51 59.74 58.64 57.91 57.94 57.93 56.98

31.30 29.25 28.19 27.58 26.71 25.90 23.73 18.54 16.05 15.46 12.03 42.04 40.41 39.32 0.00 0.74 1.73 3.15 5.01 8.66 11.92 17.63 0.00 1.05 1.27 2.98 3.34 3.83 4.02 7.74 39.54 38.18 36.86 34.69 32.94 15.14 14.93 14.73 14.68 14.42 15.22 14.32

6.42 8.45 9.12 10.50 11.08 11.44 11.94 13.05 13.86 14.19 15.57 0.50 0.48 0.44 43.14 41.14 40.08 39.07 35.38 30.92 25.77 18.58 29.33 27.52 26.88 26.05 25.54 24.56 24.29 19.89 0.00 0.42 1.96 2.47 4.55 0.00 1.66 3.03 3.66 5.78 8.00 12.59

0.00 15.30 18.61 25.81 34.83 37.75 41.92 58.35 60.94 63.46 66.90 0.00 13.42 17.24 46.66 47.08 47.08 45.62 46.33 45.35 45.26 43.26 67.90 68.43 68.71 67.71 67.70 67.84 67.84 67.86 22.29 21.38 20.60 20.51 19.50 80.50 78.27 76.75 75.95 74.15 71.39 67.92

82.98 65.72 61.50 53.73 46.06 43.18 38.64 24.44 20.96 19.05 14.43 98.82 85.56 81.85 0.00 0.94 2.19 4.06 6.66 11.96 17.31 27.62 0.00 1.16 1.41 3.31 3.74 4.34 4.57 9.00 77.71 77.76 75.39 74.20 70.73 19.50 19.56 19.28 19.25 18.45 18.76 17.07

17.02 18.98 19.90 20.46 19.11 19.07 19.44 17.21 18.10 17.49 18.67 1.18 1.02 0.92 53.34 51.98 50.73 50.32 47.01 42.70 37.43 29.11 32.10 30.41 29.88 28.98 28.57 27.82 27.60 23.14 0.00 0.86 4.01 5.28 9.77 0.00 2.17 3.97 4.80 7.40 9.86 15.01

165.11 124.67 118.15 94.82 72.44 66.72 62.84 31.84 30.60 23.24 19.92 135.07 111.73 108.16 23.64 26.36 26.57 28.80 32.87 38.08 45.24 56.69 9.43 10.50 11.15 11.23 11.84 13.26 13.61 16.33 96.54 103.67 104.54 113.90 114.73 28.78 31.01 30.89 31.15 27.98 23.23 19.20

Car + K Car + K Car + K + MZ K + MZ K + MZ K + MZ K + MZ + KZ MZ + KZ MZ + KZ MZ + KZ MZ + KZ + Z Car + Bis Car + Bis Car + Bis KZ + K KZ + K KZ + K KZ + K KZ + K KZ + K KZ + K KZ + K KZ + Z KZ + Z KZ + Z KZ + Z KZ + Z KZ + Z KZ + Z KZ + Z MZ + Bis MZ + Bis + Car MZ + Car MZ + Car MZ + Car MZ + Z MZ + Z MZ + Z MZ + Z MZ + Z MZ + Z MZ + Z

a Note: K−KCl, Z−ZnCl2, Bis−MgCl2·6H2O, Car−KCl·MgCl2·6H2O, KZ−2KCl·ZnCl2, MZ−MgCl2·ZnCl2·5H2O. wb, mass fraction of component b in saturated solution. Standard uncertainty u are u(T) = 0.1 K, u(P) = 0.9 KPa, u(w(KCl)) = 0.005, u(w(MgCl2)) = 0.003, u(w(ZnCl2)) = 0.003

2.2. Experimental Method. The method of isothermal dissolution equilibrium was taken to carry out our research for the quaternary systems KCl−MgCl2−ZnCl2−H2O and KCl− MgCl2−PbCl2−H2O. Specific operations are as follows. Experiments were conducted in a series of 200 mL sealed glass bottles using 50 mL of distilled water and a proportion of salt mixture. However, at least two salts could not be dissolved completely for each sample. Then, the samples were heated by using the high temperature oil bath oscillator (HZ-9613Y) that can control the temperature at 373 ± 0.1 K. All the samples were fully shaken for 3 days and kept standing for 2 days at 373 K. When the concentrations of all components remain unchanged, dissolution equilibrium was reached. The time of dissolution equilibrium was measured for 5 days. After the

The results prefect the necessary thermodynamic data and reveal the dissolution laws of mixed salts.

2. EXPERIMENTS 2.1. Reagents and Instruments. Analytical chemicals used throughout this work were listed in Table 1. Experimental solution was prepared by using doubly deionized water. An AL104 type standard analytical balance with 110 g capacity and less than 0.1% uncertainty manufactured by the Mettler Toledo Instruments Co., Ltd. was operated to evaluate the mass of the sample. A HZ-9613Y high temperature oil bath oscillator supplied by the Jintan Jieruier Instrument co., LTD was applied to accelerate the dissolution equilibrium. 1404

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2.3. Analytical Methods. Sodium tetraphenylborate volumetric method was used to determine the content of potassium using 3.5 g·L−1 hyamine standard solution as a titrant and titan yellow as the indicator with an uncertainty of 0.005. An EDTA volumetric method was taken to measure the total concentration of Zn2+(Pb) and Mg2+ at pH = 10 using Eriochrome Black-T as the indicator with an uncertainty of 0.003. An EDTA complexometric titration was used to evaluate the concentration of zinc(lead) ion at pH = 4.5 in the presence of xylenol orange as the indicator and acetic acid−sodium acetate as buffer solution with the uncertainty of 0.003. An ion balance subtraction method was used to calculate the concentration of magnesium ion with the uncertainty of 0.005. In order to increase the accuracy of the analysis, each sample was measured three times in parallel. Ion concentrations of the sample are calculated using the average of three determinations.

Figure 1. Dry salt diagram of the quaternary system KCl−MgCl2− ZnCl2−H2O at 373 K.

3. RESULTS AND DISCUSSION 3.1. The Quaternary System KCl−MgCl2−ZnCl2−H2O at 373 K. The solubilities for all components and the forms of solid phases in the quaternary system KCl−MgCl2−ZnCl2− H2O at 373 K were tabulated in Table 2. Figure 1 is the dry salt diagram of the quaternary system KCl−MgCl2−ZnCl2−H2O at 373 K that was plotted based on the solubility data. The composition of dry salt noted as Jb is the mass of the salt b in 100 g of total salts. The quaternary system KCl−MgCl2− ZnCl2−H2O consists of three ternary subsystems, namely KCl−MgCl2−H2O, KCl−ZnCl2−H2O, and MgCl2−ZnCl2− H2O. Each invariant point for these ternary subsystems was shown in Figure 1 as a point on the three sides of a right-angled triangle. In Table 2 and Figure 1, points A and B are the invariant points of the ternary systems KCl−MgCl2−H2O. Similarly, points C and D are the invariant points of the ternary system KCl−ZnCl2−H2O. Points F and G are the invariant points of the ternary system MgCl2−ZnCl2−H2O. Figure 1 shows that this quaternary system is a type of complex double salt. Three double salts KCl·MgCl2·6H2O(Car), 2KCl·ZnCl2, and MgCl2·ZnCl2·5H2O can be found. The phase diagram is made up of four invariant points, nine univariant curves, and six regions of crystallization corresponding to KCl, ZnCl2, MgCl2· 6H2O, KCl·MgCl2·6H2O(Car), 2KCl·ZnCl2, and MgCl2·ZnCl2· 5H2O. As can be seen from the Figure 1, the crystallization area of KCl is largest, whereas the crystallization area of

Figure 2. Water content diagram of the quaternary system KCl− MgCl2−ZnCl2−H2O at 373 K.

suspension has been clarified, 5 mL of supernatant was taken into 100 mL volumetric flask by using pipet speedy. The removed sample was diluted with distilled water to volume. The chemical analysis was taken to measure the composition of all components in the saturated liquid phase. The solid mixture was taken for solid phase identification by using a DX-2700 X-ray diffractometer.

Figure 3. X-ray diffraction photograph of the invariant point E1[KCl + Car + MgCl2·ZnCl2·5H2O] of the quaternary system KCl−MgCl2−ZnCl2− H2O at 373 K. 1405

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Figure 4. X-ray diffraction photograph of the invariant point E2[KCl + 2KCl·ZnCl2 + MgCl2·ZnCl2·5H2O] of the quaternary system KCl−MgCl2−ZnCl2−H2O at 373 K.

Figure 5. X-ray diffraction photograph of the invariant point E3[ZnCl2 + 2KCl·ZnCl2 + MgCl2·ZnCl2·5H2O] of the quaternary system KCl−MgCl2−ZnCl2−H2O at 373 K.

Figure 6. X-ray diffraction photograph of the invariant point E4[Bis + Car + MgCl2·ZnCl2·5H2O] of the quaternary system KCl−MgCl2−ZnCl2− H2O at 373 K.

MgCl2·6H2O is smallest. Therefore, the salt KCl has the smallest solubility, whereas the salt MgCl2·6H2O has the largest solubility. Nine univariant curves are AE1, BE4, CE2, DE3, FE4, GE3, E1E2, E2E3, and E1E4. Points E1, E2, E3, and E4 are the invariant points for the system KCl−MgCl2−ZnCl2−H2O at 373 K.

Point E1 saturates with salts KCl + MgCl2·ZnCl2·5H2O + KCl· MgCl2·6H2O and is at w(ZnCl2) = 8.53%, w(MgCl2) = 28.19%, and w(KCl) = 9.12%. Point E2 saturates with salts KCl + MgCl2· ZnCl2·5H2O + 2KCl·ZnCl2 and the composition of the corresponding liquid phase is w(ZnCl2) = 25.74%, w(MgCl2) = 23.73%, 1406

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Table 3. Solubilities of the Quaternary System KCl−MgCl2−PbCl2−H2O at 373 K and 94.77 KPaa Jänecke index Jb (g/100g dry salt)

composition of the solution, 100·wb no.

MgCl2

PbCl2

KCl

MgCl2

PbCl2

KCl

H2 O

solid phases

1, A 2 3 4 5 6 7 8, B 9 10 11 12 13 14 15, E1 16 17, E2 18 19, E3 20, C 21 22 23 24 25 26 27, D 28 29 30 31 32, F 33 34 35 36

0.00 6.83 13.22 22.70 25.72 29.56 30.26 0.00 2.96 8.31 17.71 19.97 26.94 30.00 31.64 33.54 35.14 37.77 38.66 38.07 38.77 38.29 38.27 38.34 38.56 38.58 42.22 42.20 42.11 40.94 39.83 31.40 31.36 31.52 31.42 31.53

2.14 1.94 1.73 1.46 1.21 1.02 0.98 6.76 6.05 4.56 2.16 1.79 0.90 0.72 0.66 0.55 0.50 0.47 0.42 7.23 6.08 5.13 4.15 2.10 0.92 0.52 0.00 0.13 0.34 0.53 0.69 0.00 0.10 0.22 0.47 0.58

9.02 10.42 9.56 8.62 7.31 5.87 5.45 34.20 30.28 25.57 18.11 15.71 9.88 7.56 5.91 4.46 3.32 0.98 0.42 0.00 0.12 0.18 0.20 0.24 0.24 0.38 0.50 0.49 0.48 0.46 0.42 6.45 6.42 6.38 6.12 6.04

0.00 35.59 53.94 69.25 75.12 81.10 82.47 0.00 7.53 21.62 46.63 53.30 71.42 78.37 82.81 87.00 90.20 96.30 97.87 84.04 86.21 87.82 89.79 94.25 97.08 97.72 98.83 98.55 98.09 97.64 97.29 82.96 82.79 82.69 82.66 82.65

19.18 10.11 7.06 4.45 3.53 2.80 2.67 16.50 15.40 11.86 5.69 4.78 2.39 1.88 1.73 1.43 1.28 1.20 1.06 15.96 13.52 11.77 9.74 5.16 2.32 1.32 0.00 0.30 0.79 1.26 1.69 0.00 0.26 0.58 1.24 1.52

80.82 54.30 39.00 26.30 21.35 16.10 14.85 83.50 77.07 66.52 47.68 41.93 26.19 19.75 15.47 11.57 8.52 2.50 1.06 0.00 0.27 0.41 0.47 0.59 0.60 0.96 1.17 1.14 1.12 1.10 1.03 17.04 16.95 16.74 16.10 15.83

796.06 421.10 308.00 205.06 192.06 174.35 172.55 144.14 154.52 160.15 163.30 166.88 165.11 161.23 161.71 159.40 156.67 154.97 153.16 120.75 122.37 129.36 134.63 145.82 151.76 153.29 134.08 133.54 132.94 138.49 144.26 164.20 163.99 162.33 163.09 162.12

KP + P KP + P KP + P KP + P KP + P KP + P KP + P KP + K KP + K KP + K KP + K KP + K KP + K KP + K KP + K + Car KP + Car KP + Car + P Car + P Car + P + Bis P + Bis P + Bis P + Bis P + Bis P + Bis P + Bis P + Bis Bis + Car Bis + Car Bis + Car Bis + Car Bis + Car K + Car K + Car K + Car K + Car K + Car

Note: K−KCl, P−PbCl2, Bis−MgCl2·6H2O, Car−KCl·MgCl2·6H2O, KP−KCl·2PbCl2. wb, mass fraction of component b in saturated solution. Standard uncertainty u are u(T) = 0.1 K, u(P) = 0.9 KPa, u(w((KCl)) = 0.005, u(w(MgCl2)) = 0.003, u(w(PbCl2)) = 0.003

a

with salts MgCl2·ZnCl2·5H2O + KCl·MgCl2·6H2O + MgCl2·6H2O and is at w(ZnCl2) = 10.50%, w(MgCl2) = 38.18%, and w(KCl) = 0.42%. In order to reflect the relative amount of water content, the water content diagram of the quaternary system KCl− MgCl2−ZnCl2−H2O at 373 K was drawn in Figure 2. It reveals that the water content decreases with the increasing w(ZnCl2) on the univariant curves except for curve GE3 and reaches minimum value at point D. It also means that the total salt concentration is the highest at point D. Figure 3 is the X-ray diffraction photograph at invariant point E1 where KCl, Car, and MgCl2·ZnCl2·5H2O were determined. Figure 4 is the X-ray diffraction photograph at the invariant point E2 where KCl, 2KCl·ZnCl2, and MgCl2·ZnCl2·5H2O were found. Figure 5 is the X-ray diffraction photograph at the invariant point E3 where ZnCl2, 2KCl·ZnCl2 and MgCl2·ZnCl2· 5H2O reached saturation. Figure 6 is the diffraction photograph at invariant point E4. As can be seen from Figure 6, Bis, Car, and MgCl2·ZnCl2·5H2O were determined at invariant point E4. 3.2. The Quaternary System KCl−MgCl2−PbCl2−H2O at 373 K. The solubilities of saturated solution and equilibrium

Figure 7. Dry salt diagram of the quaternary system KCl−MgCl2− PbCl2−H2O at 373 K.

and w(KCl) = 11.94%. Point E3 is at w(ZnCl2) = 55.79%, w(MgCl2) = 12.03%, and w(KCl) = 15.57%, where ZnCl2, MgCl2· ZnCl2·5H2O, and 2KCl·ZnCl2 reach saturation. Point E4 saturates 1407

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solid phases in the quaternary system KCl−MgCl2−PbCl2− H2O at 373 K were listed in Table 3. Figure 7 is the dry salt diagram of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K that was drawn according to the experimental data. At the same time, the local enlarged drawing was plotted in Figure 8. In Table 3 and Figure 7, the points A and B show

the invariant points of the ternary system KCl−PbCl2−H2O. Similarly, Point C stands for the invariant point of the ternary system MgCl2−PbCl2−H2O. Points D and F represent the invariant points of the ternary system KCl−MgCl2−H2O. It is seen from Table 3 and Figure 7 that this quaternary system is a type of complex double salt and has three double salts without any solid solution. The phase diagram contains three invariant points, seven univariant curves, and five regions of crystallization. Five solid crystallization areas for KCl, MgCl2· 6H2O(Bis), KCl·MgCl2·6H2O, KCl·2PbCl2, and PbCl2 can be found. Figure 7 demonstrates that the crystallization area of PbCl2 is the largest, whereas the crystallization area of MgCl2· 6H2O is the smallest. It reveals that the salt PbCl2 has the smallest solubility, whereas the salt MgCl2·6H2O has the largest solubility. Seven univariant curves are AE2, BE1, CE3, DE3, FE1, E1E2, and E2E3. Points E1, E2, and E3 are the invariant points for the system KCl−MgCl2−PbCl2−H2O at 373 K. Point E1 saturates with salts KCl + KCl·2PbCl2+KCl·MgCl2·6H2O and the mass fraction of the corresponding liquid phase is w(MgCl2) = 31.64%, w(PbCl2) = 0.66%, and w(KCl) = 5.91%. Point E2 saturates with salts PbCl2 + KCl·2PbCl2 + KCl· MgCl2·6H2O and is at w(MgCl2) = 35.14%, w(PbCl2) = 0.50%, and w(KCl) = 3.32%. Point E3 is at w(MgCl2) = 38.66%, w(PbCl2) = 0.42%, and w(KCl) = 0.42%, where PbCl2, MgCl2· 6H2O and KCl·MgCl2·6H2O reach saturation. Figure 9 is the water content diagram of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K. It shows that the water content changes regularly with the increasing concentration of magnesium chloride on the univariant curves. Water content decreases with the increasing J(MgCl2) at the univariant curve AE2 and reaches minimum value at the point E2, whereas there is not an obvious change at the other univariant curves. Figure 10 shows the powder X-ray diffraction picture of the invariant point E1. Compared with the standard cards of three salt minerals, KCl, Car, and KCl·2PbCl2 were determined. Figure 11 displays the X-ray diffraction photograph of the invariant point E2 where three solid phases PbCl2, Car, and KCl·2PbCl2 can be formed. Figure 12 is the X-ray diffraction photograph of the invariant point E3. It demonstrates that PbCl2, Car, and Bis reached saturation.

Figure 8. Local enlarged dry salt diagram of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K.

Figure 9. Water content diagram of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K.

Figure 10. X-ray diffraction photograph of the invariant point E1[KCl + Car + KCl·2PbCl2] of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K. 1408

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Figure 11. X-ray diffraction photograph of the invariant point E2[PbCl2 + Car + KCl·2PbCl2] of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K.

Figure 12. X-ray diffraction photograph of the invariant point E3[PbCl2 + Car + Bis] of the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K.

4. CONCLUSIONS By using the method of isothermal solution saturation and powder X-ray diffraction, solubilities of saturated solution in the two quaternary systems KCl−MgCl2−ZnCl2−H2O and KCl− MgCl2−PbCl2−H2O were measured at 373 K. On the basis of experimental results, we have drawn two phase diagrams as well as corresponding water content diagrams according to the principle of phase law. It was concluded that these two phase diagrams for quaternary systems belong to the complex double salt type owing to existing double salts. As a result, six solid phases KCl, ZnCl2, MgCl2·6H2O, KCl·MgCl2·6H2O(Car), 2KCl·ZnCl2, and MgCl2·ZnCl2·5H2O were determined by XRD in the quaternary system KCl−MgCl2−ZnCl2−H2O. It was demonstrated that five precipitates KCl, MgCl2·6H2O, KCl·MgCl2·6H2O(Car), KCl·2PbCl2, and PbCl2 were formed in the quaternary system KCl−MgCl2−PbCl2−H2O at 373 K.

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research and innovation team in Universities of Sichuan Provincial Department of Education (15TD0009).

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REFERENCES

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: 13032845233. Notes

The authors declare no competing financial interest. Funding

This project was supported by the National Natural Science Foundation of China (41373062, U1407108), and scientific 1409

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DOI: 10.1021/acs.jced.6b00960 J. Chem. Eng. Data 2017, 62, 1403−1410