Article pubs.acs.org/jced
Equilibria in the Quaternary System Na+,K+//Cl−,B4O72−−H2O at 323 K Xiao Zhang,†,‡,∥ Shi-Hua Sang,*,†,‡,§ Si-Yao Zhong,†,§ and Xiang-Po Zhao†,§ †
College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, Sichuan, China Department of Geochemistry, Chengdu University of Technology, Chengdu 610059, Sichuan, China § Mineral Resources Chemistry, Key Laboratory of Sichuan Higher Education Institutions, Chengdu 610059, Sichuan, China ∥ Sichuan Zhiyuan Engineering Detecting Co. Ltd., Chengdu 610031, Sichuan, China ‡
ABSTRACT: The experimental studies on phase equilibria in the quaternary system Na+,K+//Cl−,B4O72−−H2O at 323 K were done by the method of isothermal solution saturation. Solubilities of salts and densities of the solution were determined experimentally. The experimental results show that there is no double salt in the quaternary system Na+,K+// Cl−,B4O72−−H2O at 323 K. The equilibrium phase diagram and the density-composition diagram were plotted based on the experimental data. In the phase diagram, the quaternary system has two invariant points, five univariant curves, and four crystallization fields corresponding to Na2B4O7·10H2O, K2B4O7·4H2O, NaCl, and KCl. A brief discussion of the experimental results is described.
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phase equilibria of Na+,K+//Cl−,B4O72−−H2O system and densities of the liquid phase at 323 K were studied by the method of isothermal solution saturation. Based on the experimental results, the equilibrium phase diagram and the density−composition diagram were plotted. This research will provide solubility data for the extraction of potassium and boron in the gas field.
INTRODUCTION The total amount of brine water resources in the gas field is the largest in China, and the gas field brine water in west Sichuan Basin is widely distributed. It has a high value of exploitation and utilization. Therefore, a study on the utilization of the Sichuan Basin will certainly be able to promote the rapid development of China’s fertilizer industry and the brine chemical industry can produce great social and economic benefits.1−4 Some scholars have conducted research on the phase equilibria of water−salt system under 323 K. Zeng et al.5 investigated the phase equilibria of the Li+,K+//Cl−,B4O72−− H2O system; Sun et al.6 reported the Na+//Br−,SO42−−H2O ternary system; Shi et al.7 studied the Li+//SO42−,B4O72−−H2O ternary system; Wang et al.8 studied the K+,NH4+//Cl−,SO42−− H2O quaternary interaction system; Ren et al.9 studied the solubility of the Li+,K+//Cl−,SO42−−H2O quaternary interaction system at 50 °C and 75 °C. The gas field brine water in west Sichuan Basin can be simplified to the quinary system Na+,K+//Cl−,SO42−,B4O72−− H2O. There are some publications we have finished before: the phase equilibrium of the Na+,K+//Cl−,SO42−,B4O72−−H2O system at 298 K and 323 K;10,11 the phase equilibria of the Na+//Cl−,SO42−,B4O72−−H2O system at 323 K;12 the phase equilibria of the K+//Cl−,SO42−,B4O72−−H2O system at 323 K;13 the phase equilibria of the Na+,K+//Cl−,B4O72−−H2O system at 288 K and 298 K,14,15 the phase equilibria of the K+// Cl−,Br−,SO42−−H2O system at 348 K;16 the phase equilibria of the K+//Cl−,Br−,B4O72−−H2O system at 373 K.17 But so far no solubility data on the Na+,K+//Cl−,B4O72−−H2O system has been reported by any literature at 323 K. In this paper, the © 2014 American Chemical Society
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EXPERIMENTAL SECTION Instruments and Reagents. All of the reagents were in analytical purity grade and obtained from the following suppliers: AgNO3 and K2CrO4 (Beijing Chemical Reagent Factory, China), Na2B4O7·10H2O, K2B4O7·4H2O, NaCl, and KCl (Chengdu KeLun Chemical Reagent Factory, China). Distilled water with a conductivity less than 1·10−4 S/m and pH = 6.6 was used for preparation for the measurement solubility experiments and chemical analysis. Other equipment included an AL104 electronic scale (from Mettler-Toledo, 0.0001 g accuracy), HZS-H type thermostatic vibrator with a precision of ± 0.1 K (from Ha Erbin Donglian), X-ray powder crystal diffraction meter (from Japan, Rigaku D/ max-3C), and ICP-OES (from Perkin-Elmer). Experimental Method. The equilibrium experiments were done by the method of isothermal solution saturation. The system points for quaternary system were obtained by adding the third component gradually on the basis of the ternary subsystem salt saturation points at 323 K (± 0.1 K). The Received: November 2, 2013 Accepted: January 30, 2014 Published: February 7, 2014 821
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Table 1. Experimental Solubilities and Solution Densities of the Quaternary System Na+,K+//Cl−,B4O72−−H2O at 323 Ka Jänecke index/mol·100 mol−1 (2Na+ + 2K+ = 100 mol)
composition of solution 100w(B)b
density
no.
w(Na+)
w(K+)
w(Cl−)
w(B4O72−)
J(2K+)
J(2Cl−)
J(H2O)
solid phasec
ρ/g·cm−3
1(E1) 2 3 4 5 6 7(F1) 8(E2) 9 10 11 12 13 14 15(E4) 16 17 18 19 20 21 22(E3) 23 24 25 26 27 28(F2)
2.26 1.95 1.92 2.12 2.18 1.89 2.06 0.00 0.94 1.81 3.41 3.63 4.04 5.39 10.54 10.21 9.91 8.97 8.08 6.73 6.22 7.55 7.46 7.52 7.42 7.31 6.78 6.25
8.08 8.31 8.49 8.70 9.91 10.47 12.86 15.70 14.83 14.11 12.44 12.26 11.48 9.76 0.00 0.89 1.68 3.00 4.50 6.07 7.99 7.44 7.42 7.44 7.51 7.56 7.62 8.88
0.00 1.42 2.72 4.17 6.99 8.02 12.02 12.69 12.73 12.83 12.56 12.54 13.35 15.23 15.38 15.65 15.87 15.58 15.43 14.49 15.25 18.43 17.53 17.20 17.14 17.06 16.22 16.16
23.71 20.00 17.42 15.36 11.80 9.68 6.25 3.86 4.86 6.14 8.82 9.24 7.30 4.31 1.96 2.02 2.08 2.17 2.49 3.12 3.55 0.00 1.61 2.57 2.52 2.42 2.58 3.41
67.97 71.55 72.32 70.78 72.80 76.55 78.67 100.00 90.32 82.11 68.24 66.55 62.65 51.66 0.00 4.90 9.08 16.47 24.74 34.72 43.13 36.75 36.96 36.86 37.36 37.91 39.86 45.60
0.00 13.47 25.43 37.24 56.45 64.41 80.78 88.94 85.14 82.03 75.69 74.78 79.98 88.53 94.50 94.42 94.35 94.01 93.12 91.03 90.36 100.00 95.97 93.59 93.70 93.91 93.22 91.20
2408.50 2547.30 2561.71 2451.47 2198.24 2214.53 1769.45 1846.37 1756.96 1640.43 1491.08 1465.10 1507.07 1496.09 1746.06 1692.90 1650.00 1670.63 1652.61 1722.91 1564.26 1423.68 1422.99 1399.37 1408.61 1424.16 1513.41 1451.90
KB+NB KB+NB KB+NB KB+NB KB+NB KB+NB KB+NB+KL KB +KL KB +KL KB +KL NB+KL NB+KL NB+KL NB+KL NB+NL NB+NL NB+NL NB+NL NB+NL NB+NL NB+NL KL+NL KL+NL KL+NL KL+NL KL+NL KL+NL NB+KL+NL
1.3215 1.2774 1.2708 1.2593 1.2472 1.2351 1.2635 1.2352 1.2485 1.2605 1.2922 1.2970 1.2776 1.2632 1.2049 1.2132 1.2185 1.2232 1.2239 1.2257 1.2454 1.2399 1.2538 1.2618 1.2619 1.2619 1.2602 1.2545
Standard uncertainties u are u(T) = 0.1 K, u(ρ) = 0.0002 g·cm−3, and u(w) = 0.005. bw(B) is the mass fraction of component B. cNB, Na2B4O7· 10H2O; KB, K2B4O7·4H2O; KL, KCl; NL, NaCl.
a
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respective mixtures were placed in bottles of 100 mL for the solubility experiments and the bottles placed in the thermostatic vibrator (HZS-H). The bottles with solution were stirred to promote the establishment of equilibrium. Equilibrium was reached when the components of the solution was no longer changing. The time to reach equilibrium was about 10 days. The solutions were taken out periodically for chemical analysis. After it reached the equilibrium point, the compositions of solution were determined by chemical analysis. Wet crystals were separated from the solution by vacuum filtration using a sintered glass crucible and dried for X-ray diffraction. A Rigaku D/max-3C X-ray diffraction analyzer (Japan) was used for the X-ray diffraction analysis of solids. The densities of the solution were determined by pycnometer with an uncertainty of 0.0002 g·cm−3. Analytical Methods.18 The concentration of potassium ion (K+) was determined by sodium tetraphenylborate−hexadecyl trimethyl ammonium bromide titration (uncertainty of 0.5 %). The concentration of B4O72− was evaluated by basic titration with the existence of mannitol (precision: ± 0.3 %). The concentration of Cl− was determined by titration with silver nitrate standard solution in the presence of potassium dichromate (uncertainty ± 0.3 %). The concentration of sodium ion (Na+) was evaluated according to the ion balance.
RESULTS AND DISCUSSION
The experimental results of solubilities and densities for the quaternary system Na+,K+//Cl−,B4O72−−H2O at 323 K are determined and are tabulated in Table 1. The respective ion concentration values are expressed in mass fraction w. The solution density (ρ) is given in grams per centimeter. Jänecke index values are used for plotting the quaternary system diagram. The respective ion Jänecke index values J are calculated according to defined correlations: [b]: mole value per 100 g of solution [2K+] = 100w(K+)/78, [2Na+] = 100w(Na+)/46, [2Cl−] = 100w(Cl−)/71 J(2K+) (Jänecke index value of K+) = 100·[2K+]/([2Na+] + [2K+]) J(2Cl−) (Jänecke index value of Cl−) = 100·[2Cl−]/([2Na+] + [2K+]) J(H2O) (Jänecke index value of H2O) = 100·[H2O]/([2Na+] + [2K+]) According to experimental data, the equilibrium phase diagram (Figure 1), water content diagram (Figure 2), and the density−composition diagram (Figure 3) are plotted, respectively. In Figure 1, points E1, E2, E3, and E4 represent the invariant points of the ternary systems of Na+,K+//B4O72−−H2O, K+// Cl−,B4O72−−H2O, Na+,K+//Cl−−H2O, and Na+//Cl−,B4O72−− H2O at 323 K, respectively. There are four crystallization zones: Na2B4O7·10H2O, K2B4O7·4H2O, NaCl, KCl, two invariant 822
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Figure 1. Phase diagram of the quaternary system Na+,K+// Cl−,B4O72−−H2O at 323 K.
Figure 3. Composition−density diagram of the quaternary system Na+,K+//Cl−,B4O72−−H2O at 323 K.
NaCl. The crystallization area of Na2B4O7·10H2O in the phase diagram is the biggest among other crystallization areas, so the solubility of Na2B4O7·10H2O is lower than that of K2B4O7· 4H2O, NaCl, and KCl at 323 K. The crystallization area NaCl in the phase diagram is smaller than other crystallization areas, so the solubility of NaCl is bigger than that of K2B4O7·4H2O, Na2B4O7·10H2O, and KCl at 323 K. From Figure 3 we can see that the equilibrium solution density values in the system Na+,K+//Cl−,B4O72−−H2O at 323 K do not change much. Comparing the equilibrium diagram of the system Na+,K+// − Cl ,B4O72−−H2O at 288 K14and 298 K,15 we can see that the crystallization area of Na2B4O7·10H2O at 298 K is smaller than that at 288 K, and the crystallization areas of K2B4O7·4H2O, NaCl, and KCl at 298 K are all bigger than that at 288 K. Comparing the equilibrium diagram of the system Na+,K+// Cl−,B4O72−−H2O at 323 K and 298 K,15 we can see that the crystallization area of Na2B4O7·10H2O at 323 K is smaller than that at 298 K, and the crystallization areas of K2B4O7·4H2O, NaCl, and KCl at 323 K are all bigger than that at 298 K. Therefore, the temperature is higher, the crystallization area Na2B4O7·10H2O is smaller, and the crystallization areas of K2B4O7·4H2O, NaCl, and KCl are bigger. In this system, the solubilization effect can be seen with cooling for K2B4O7·4H2O, NaCl, and KCl.
Figure 2. Water content diagram of the quaternary system Na+,K+// Cl−,B4O72−−H2O at 323 K.
points F1 and F2, and five univariant curves E1F1, E2F1, E3F2, F1F2, and F2E4. The invariant point F1 corresponds to the solution saturated with the salts Na2B4O7·10H2O, K2B4O7· 4H2O, and KCl with mass fraction (100w): w(Na+) 2.06 %, w(K+) 12.86 %, w(Cl−) 12.02 %, w(B4O72−) 6.25 %. The invariant point F2 corresponds to the solution saturated with the salts Na2B4O7·10H2O, NaCl, and KCl with mass fraction (100w): w(Na+) 6.25 %, w(K+) 8.88 %, w(Cl−) 16.16 %, w(B4O72−) 3.41 %. The E1F1 curve is the solubility isotherm where the solution was saturated with Na2B4O7·10H2O and K2B4O7·4H2O; the E2F1 curve is the solubility isotherm where the solution was saturated with K2B4O7·4H2O and KCl; the E3F2 curve is the solubility isotherm where the solution was saturated with NaCl and KCl; the F1F2 curve is the solubility isotherm where the solution was saturated with Na2B4O7· 10H2O and KCl; the F2E4 curve is the solubility isotherm where the solution was saturated with Na2B4O7·10H2O and
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CONCLUSION On the basis of the experimental results, we naturally come to the following conclusions. In the quaternary system Na+,K+//Cl−,B4O72−−H2O at 323 K, no double salt is found. There are four single salt crystallization zones: Na2B4O7·10H2O, K2B4O7·4H2O, NaCl, KCl, two invariant points, and five univariant curves. The crystallization area of Na2B4O7·10H2O in the phase diagram is bigger than other crystallization areas, so the solubility of Na2B4O7·10H2O is smaller than those of K2B4O7·4H2O, NaCl, and KCl at 323 K; the crystallization area of NaCl in the phase diagram is smaller than other crystallization areas, so the solubility of NaCl is bigger than those of K2B4O7·4H2O, Na2B4O7·10H2O, and KCl at 323 K. The density data from the experiments show that the equilibrium solution density values 823
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in the system Na+,K+//Cl−,B4O72−−H2O at 323 K do not change much.
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(18) Institute of Qinghai Salt-Lake, Chinese Academy of Science. Analytical methods of brines and salts; Science Press: Beijing, 1988 (in Chinese).
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Funding
This project was supported by the National Natural Science Foundation of China (no. 41373062, 40973047) and the Specialized Research Fund (20125122110015) for the Doctoral Program of Higher Education of China. Notes
The authors declare no competing financial interest.
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