Solid–Liquid Metastable Phase Equilibria in the Five-Component

Article pubs.acs.org/jced

Solid−Liquid Metastable Phase Equilibria in the Five-Component System (Li + Na + K + Cl + SO4 + H2O) at 308.15 K Yuanhui Liu, Yafei Guo, Xiaoping Yu, Shiqiang Wang, and Tianlong Deng* Tianjin Key Laboratory of Marine Resources and Chemistry, College of Marine Science and Technology at Tianjin University of Science and Technology, Tianjin 300457, P. R. China ABSTRACT: The metastable equilibrium solubilities and the physicochemical properties including refractive index, density, viscosity, conductivity, and pH for the aqueous reciprocal five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K were studied using the isothermal evaporation method. According to the experimental data, the dry-salt-phase diagram, sodium-phase diagram, water-phase diagram, and the diagrams of physicochemical properties versus composition were plotted. The dry-salt-phase diagram of the five-component system includes seven four-salt cosaturated points, fourteen univariant solubility curves, and eight crystallization zones all saturated with sodium chloride. Three kinds of double salts of lithium salts (Db1, Li2SO4·3Na2SO4·12H2O; Db2, Li2SO4·Na2SO4; Db3, 2Li2SO4·Na2SO4·K2SO4) were found, and no solid solution was formed in the metastable five-component system. Because the Pitzer mixing ion-interaction parameters containing lithium and sodium such as θLi,Na, ΨLi,Na,Cl, and ΨLi,Na,SO4 at 308.15 K are scarce, the solubilities of the five-component system at 298.15 K were calculated on the basis of Pitzer’s ioninteraction theory and the chemical equilibrium Harvie−Møller−Weare model (HMW model). A comparison of the calculated phase diagram at 298.15 K and the experimental phase diagram at 308.15 K was also carried out.

■

calculating solubilities.6 On the basis of the semiempirical equations of Pitzer,7−9 which gave a set of expressions for osmotic coefficients of the solution and mean activity coefficients of electrolytes in the solution, the Harvie− Møller−Weare solubility modeling approach has extended the electrolyte model,10−17 which reliably predict mineral solubilities in complex brine systems from low to high concentrations for the stable solubility predictions of the major seawater ions of the five-component system (Na + K + Mg + Cl + SO4 + H2O)8,11 and the ternary and quaternary subsystems of the complex system (Na + K + Ca + Mg + H + Cl + SO4 + CO2 + B(OH)4 + H2O) in Searles Lake, California.18 Using the Pitzer parameters and the standard chemical potential of the aqueous solution species and minerals allow us to identify the solids existed and their compositions at equilibrium. But for the metastable solubility prediction in the metastable fivecomponent system at 308.15 K, there are two key problems: (1) the Pitzer mixing ion-interaction parameters containing lithium and sodium such as θLi,Na, ΨLi,Na,Cl, and ΨLi,Na,SO4 at 308.15 K are scarce; (2) there is no way to obtain the metastable equilibrium contents of solids due to the fact that the standard chemical potential of the species and minerals in the aqueous solution is unsuitable for the metastable solubility prediction. Fortunately, although there is no report on the experimental solubility data of the same five-component system

INTRODUCTION Salt lakes are naturally formed complex multicomponent systems of water and salt interaction. A number of salt lakes with abundance of lithium, potassium, magnesium, and borate resources are widely distributed in the Qinghai-Tibet Plateau, China. The composition of the brine mostly belongs to the complex eight-component system (Li + Na + K + Mg + Cl + SO4 + B4O7 + CO3 + H2O). In order to economically exploit the brine and mineral resources, it is well-known thermodynamic phase equilibria and phase diagrams play an important role in exploiting the brine resources and describing the geochemical behavior of brine and mineral systems. However, the phenomena of supersaturation of the brines containing sulfate and borate are often found both in salt lakes and solar ponds.1 Therefore, the metastable phase equilibrium solubilities and phase diagrams are essential to predict the actual evaporating path of mineral crystallization to guide the separation and purification of the lithium and potassium-containing mixture salts effectively. As a part of the complex system, the metastable phase diagrams of some five-component subsystems of the complex eight-component system at (288.15 and 298.15) K have been reported.2−5 However, the thermodynamic metastable phase diagram at 308.15 K and the stable phase diagram at 298.15 K for the five-component system (Li + Na + K + Cl + SO4 + H2O) are not reported in the literature. Because the solubilities of salts in a multicomponent salt− water system are generally a few molality, it is necessary to use a reliable theory for aqueous solutions of electrolytes in © 2014 American Chemical Society

Received: February 11, 2014 Accepted: March 24, 2014 Published: April 2, 2014 1685

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

HMW model. Then, a comparison of the calculated stable equilibrium phase diagram at 298.15 K and the experimental metastable equilibrium phase diagram at 308.15 K was carried out.

Table 1. Chemical Samples Used in This Study initial chemical mass a name source fraction Lc H Syl Ls Th Ar

A.R.b A.R.b A.R.b A.R.c A.R.c A.R.c

0.99 0.99 0.995 0.999 0.99 0.995

purification method

final mass fraction

analysis method

■

recrystallization 0.995 titration method for Cl− recrystallization 0.998 titration method for Cl− none titration method for Cl− none gravimetric method for SO42− recrystallization 0.998 gravimetric method for SO42− none gravimetric method for SO42−

EXPERIMENTAL SECTION Apparatus and Reagents. The isothermal evaporation box was made in our laboratory, which was described in our previously work.19 Briefly, a simulated natural evaporation box was designed, and it was easy to control the isothermal evaporation condition at (308.15 ± 0.2) K in our laboratory. The chemicals used were of analytical grade, and some of them were recrystallized before use in Table 1. They were all obtained from either the Tianjin Kermel Chemical Reagent Ltd. or the Shanghai-Lithium Industrial Co. Ltd.: lithium chloride (LiCl, 0.99 in mass fraction), sodium chloride (NaCl, 0.99), potassium chloride (KCl, 0.995), lithium sulfate (Li2SO4·H2O, 0.999), sodium sulfate (Na2SO4, 0.99), and potassium sulfate (K2SO4, 0.995). Double deionized water (DDW) with a conductivity less than 1·10−4 S·m−1 and pH 6.60 at 298.15 K was

a

Lc, lithium chloride, LiCl; H, hsodium chloride, NaCl; potassium chloride, KCl; Ls, lithium sulfate, Li2SO4; Th, sodium sulfate, Na2SO4; Ar, potassium sulfate, K2SO4. bA.R. from the Shanghai Lithium Industrial Co. Ltd. cA.R. from the Tianjin Kermel Chemical Reagent Ltd.

at 298.15 K, the Pitzer single-salt parameters, Pitzer mixing ioninteraction parameters, and μ0/RT values of the species in the five-component system at 298.15 K were all reported in the literature.6,11 Therefore, the predictive solubilities of the fivecomponent system at 298.15 K were predicted on the basis of Pitzer’s ion-interaction theory and the chemical equilibrium

Table 2. Solubilities of the Metastable Five-Component System (Li + Na + K + Cl + SO4 + H2O) All Saturated with NaCl at T = 308.15 K and p = 0.1 MPaa composition of liquid phase, 100wb

Jänecke index, J/[mol/100 mol (2Li+ + SO42− + 2K+)]

no.

Li+

Na+

K+

Cl−

SO42−

H2O

J(2Li+)

J(SO42−)

J(2K+)

J(2Na+)

J(H2O)

equilibrium solid phasesc

1, H 2 3, A 4 5, I 6 7, B 8 9, J 10 11, C 12 13, D 14, K 15 16 17, E 18 19, L 20 21 22 23 24 25 26, F 27 28 29 30 31, G 32, M 33, N

0.91 1.02 0.95 1.07 1.34 1.35 1.51 1.99 3.23 3.10 2.93 3.26 3.73 0.00 0.11 0.24 0.60 0.68 0.00 0.091 0.14 0.21 0.30 0.58 0.77 0.87 0.54 0.96 1.13 3.19 7.18 7.62 6.96

8.88 8.30 8.16 7.91 7.49 7.30 6.79 5.21 2.36 2.45 2.86 2.27 1.36 9.62 9.34 8.95 8.20 8.53 7.96 7.71 7.66 7.49 7.28 6.68 6.16 6.04 8.17 5.81 5.39 2.09 0.95 1.58 1.43

0.00 0.57 1.11 0.89 0.00 0.33 0.74 0.68 0.00 0.37 0.62 1.62 2.51 3.81 3.79 3.89 3.66 2.11 6.66 6.65 6.55 6.50 6.42 6.29 6.10 5.95 3.90 5.87 5.70 3.10 1.99 0.00 2.30

13.80 13.80 13.96 13.88 14.11 14.30 14.66 15.94 19.25 18.83 18.63 21.08 23.11 14.84 14.75 14.67 14.54 14.27 17.09 17.12 17.12 17.11 17.14 17.37 17.06 17.22 14.86 17.46 17.72 21.63 39.94 41.36 39.84

6.19 6.42 6.09 6.22 5.80 5.67 5.72 3.90 1.22 1.49 1.79 0.70 0.41 4.67 4.93 5.27 6.10 5.81 1.66 1.71 1.81 1.91 1.96 2.20 2.55 2.59 5.45 2.32 2.09 0.92 0.032 0.028 0.00

70.22 69.88 69.73 70.03 71.26 71.05 70.58 72.28 73.94 73.77 73.17 71.08 68.88 67.06 67.08 66.98 66.91 68.60 66.64 66.72 66.74 66.78 66.90 66.88 67.37 67.33 67.08 67.58 67.96 69.08 49.91 49.41 49.47

50.56 49.84 46.96 50.31 61.48 60.67 61.29 74.40 94.82 91.71 88.84 89.34 88.08 0.00 7.22 14.17 28.24 35.94 0.00 6.00 8.82 12.89 17.54 28.96 34.58 37.67 26.55 40.97 46.28 82.36 95.27 99.95 94.45

49.44 45.20 43.33 42.26 38.52 36.71 33.43 21.08 5.18 6.36 7.84 2.78 1.39 49.99 47.68 44.98 41.30 44.27 16.83 16.26 16.72 16.82 16.42 15.72 16.63 16.31 39.07 14.36 12.36 3.43 0.062 0.053 0.00

0.00 4.96 9.71 7.43 0.00 2.62 5.28 4.52 0.00 1.93 3.32 7.88 10.53 50.01 45.10 40.85 30.46 19.79 83.17 77.74 74.46 70.29 66.04 55.32 48.79 46.02 34.38 44.67 41.36 14.21 4.67 0.00 5.55

148.24 121.98 121.24 112.16 103.90 98.78 83.01 58.78 20.84 21.89 26.22 18.81 9.66 215.05 188.89 159.63 115.98 135.82 168.88 153.28 148.17 137.86 127.30 99.87 83.80 79.45 122.44 75.29 66.42 16.33 3.81 6.26 5.86

2991.6 2622.3 2645.6 2535.4 2522.0 2452.2 2200.9 2081.1 1670.6 1682.9 1709.2 1503.3 1253.5 3824.3 3463.1 3049.1 2416.3 2787.1 3610.6 3386.1 3295.3 3136.6 2986.6 2552.1 2340.4 2259.6 2564.3 2233.6 2138.7 1376.3 510.0 499.1 517.3

Th + Db1 + H Th + Db1 + H Th + Db1 + Db3 + H Db1 + Db3 + H Db1 + Db2 + H Db1 + Db2 + H Db1 + Db2 + Db3 + H Db2 + Db3 + H Db2 + Ls + H Db2 + Ls + H Db3 + Db2 + Ls + H Ls + Db3 + H Db3 + Syl + Ls + H Ap + Th + H Ap + Th + H Ap + Th + H Ap + Th + Db3 + H Th + H + Db3 Ap + Syl + H Ap + Syl + H Ap + Syl + H Ap + Syl + H Ap + Syl + H Ap + Syl + H Ap + Syl + H Ap + Syl + Db3 + H Ap + Db3 + H Db3 + Syl + H Db3 + Syl + H Db3 + Syl + H H + Syl + Ls + Lc H + Ls + Lc H + Syl + Lc

a Standard uncertainties u are u(T) = 0.1 K and u(p) = 0.005 MPa. u(x) for Li+, K+, Na+, Cl−, and SO42− are 0.005, 0.0005, 0.005, 0.0003, and 0.0005 in mass fraction, respectively. bw, in mass fraction. cH, NaCl; Th, Na2SO4; Syl, KCl; Ap, NaK3(SO4)2; Db1, Li2SO4·3Na2SO4·12H2O; Db2, Li2SO4· Na2SO4; Db3, 2Li2SO4·Na2SO4·K2SO4; Ls, Li2SO4·H2O; Lc, LiCl·H2O.

1686

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

used to prepare the series of the artificial synthesized brines and for chemical analysis. Experimental Method. Unlike the thermodynamic stable phase equilibrium, which was studied in a closed container in the presence of vigorously stirring to accelerate the solid and liquid phase equilibrium, for the metastable phase equilibrium study, an isothermal evaporation method was adopted and described in our previous work.19 In other word, it was studied using the isothermal evaporating approach in an opening container without stirring to simulate the natural evaporating condition. This isothermal evaporation method was introduced previously.19−21 Briefly, for the isothermal evaporation, the crystallization behavior of the brines with a series of the artificially synthesized complex in the opening container was observed periodically. When a new solid phase appeared, the solid phase was carefully taken out without stirring and washed three times with DDW and sucked dry with filter paper. Then, the solids were evaluated with a combined observation using an oil immersion by a BX51 digital polarizing microscopy (Olympus, Japan) and further identification with an X-ray diffractometer (X’pert PRO, Spectris. Pte. Ltd., The Netherland). The liquid phase of the clarified solution was taken for either the chemical analysis or physicochemical property measurement according to the analytical method. The remainder of the solution continued to be evaporated to reach a new metastable equilibrium point. Analytical Method. The concentrations of SO42− and K+ ions were analyzed in triplicate using the gravimetric method with barium chloride and sodium tetraphenyl borate, respectively, both with an uncertainty of ± 0.0005 in mass fraction.22 The Cl− ion concentration was determined in triplicate by titration with mercury nitrate standard solution in the presence of a mixed indicator of diphenylcarbazone and bromophenol blue with an uncertainty ± 0.003 in mass fraction.22 The Li+ ion concentration was determined by an inductively coupled plasma optical emission spectrometer (ICP-OES, Prodigy, Leman Corporation, America) with an uncertainty of ± 0.005 in mass fraction, and the Na+ ion concentration was evaluated according to ion balance. A precision pH meter (PHSJ-5, Shanghai Precision Scientific Instruments Co. Ltd., China) was used to measure the pH of the equilibrium aqueous solutions in triplicate with uncertainty within ± 0.01. The viscosities (η) were determined using an Ubbelohde capillary viscometer with five replicates with an uncertainty 0.2 mPa·s. Conductivities (κ) were measured with an Orion 145A+ conductivity meter (Thermo Electron Corporation, America) with an uncertainty within ± 0.01 S·m−1. The densities (ρ) were measured using an automatic temperature control digital vibrating-tube densimeter (DMA 4500, Anton Paar Co. Ltd., Austria) with an uncertainty of ± 0.1 mg·cm−3. The refractive indices (nD) were measured using the automatic temperature control refractometer (Abbemat 550, Anton Paar Co. Ltd., Austria) with an uncertainty within ± 0.0001. The measurement of the physicochemical parameters of pH, viscosity, and conductivity were all undertaken in a thermostat that was electronically controlled the set temperature at (308.15 ± 0.1) K.

Table 3. Physicochemical Properties on Refractive Indices (nD), Densities (ρ), Viscosities (η), Conductivities (κ), and pH Values for the Five-Component System (Li + Na + K + Cl + SO4 + H2O) at T = 308.15 K and p = 0.1 MPaa ρ

η

κc

no.b

nD

g·cm−3

mPa·s

S·m−1

pH

1, H 2 3, A 4 5,I 6 7, B 8 9,J 10 11,C 12 13, D 14, K 15 16 17,E 18 19, L 20 21 22 23 24 25 26, F 27 28 29 30 31, G 32, M 33, N

1.3919 1.3926 1.3850 1.3848 1.3916 1.3918 1.3926 1.3842 1.3933 1.3939 1.3939 1.3907 1.3989 1.3938 1.3933 1.3941 1.3948 1.3860 1.3940 1.3941 1.3941 1.3941 1.3941 1.3948 1.3951 1.3874 1.3864 1.3951 1.3963 1.3930 1.4378 1.4382 1.4487

1.2296 1.2326 1.2344 1.2315 1.2187 1.2187 1.2200 1.1950 1.1631 1.1672 1.1716 1.1772 1.1935 1.2608 1.2588 1.2607 1.2607 1.2560 1.2511 1.2491 1.2489 1.2474 1.2453 1.2430 1.2403 1.2378 1.2553 1.2335 1.2279 1.1935 1.3049 1.2953 1.3284

2.0550 2.0807 2.0395 2.0616 2.0516 2.0334 2.0300 1.9607 1.9656 1.9467 1.9547 2.0769 2.3904 1.7676 1.7988 1.8377 1.9563 1.9224 1.4856 1.5009 1.5185 1.5304 1.5444 1.5819 1.6483 1.6692 1.8781 1.6721 1.6704 2.1487 11.2967 11.7737 15.8951

ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND 8.43 8.38 7.58

8.15 8.13 7.84 7.98 8.00 8.08 7.96 7.58 6.20 6.38 6.51 5.92 6.33 6.79 7.29 7.52 7.78 7.74 6.56 6.52 6.58 6.51 6.84 7.64 7.86 8.07 7.96 7.85 7.86 7.26 5.53 4.84 5.73

a Standard uncertainties u are u(T) = 0.1 K and u(p) = 0.005 MPa. u(x) for nD, ρ, η, κ, and pH are 0.0001, 0.1 mg·cm−3, 0.2 mPa·s, 0.01, and 0.01, respectively; bThe no. column corresponds to the no. column in Table 2. cND means not detected.

the metastable equilibrium solution were expressed as Jänecke indices (JB, JB/[mol/100 mol(2Li+ + 2K+ + SO42−)]) in Table 2. Using the experimental Jänecke indices in Table 2, the dry-salt phase diagram, sodium-phase diagram, and water-phase diagram of the system were plotted in Figures 1, 2, and 3, respectively. In Figure 1, the metastable phase diagram of the fivecomponent system (Li + Na + K + Cl + SO4 + H2O) consists of eight crystallization zones in which all are saturated with sodium chloride (H) corresponding to sodium sulfate (Na2SO4, Th), potassium chloride (KCl, Syl), lithium sulfate monohydrate (Li2SO4·H2O, Ls), lithium chloride monohydrate (LiCl· H2O, Lc), glaserite (Na2SO4·3K2SO4, Ap), double salt 1 (Li2SO4· 3Na2SO4·12H2O, Db1), double salt 2 (Li2SO4·Na2SO4, Db2), and double salt 3 (2Li2SO4·Na2SO4·K2SO4, Db3). There are fourteen univariant curves corresponding to curves AH (H + Th + Db1), AE (H + Th + Db3), AB (H + Db1 + Db3), BI (H + Db1 + Db2), BC (H + Db2 + Db3), CJ (H + Ls + Db2), CD (H + Ls + Db3), DG (H + Syl + Ls), FD (H + Syl + Db3),

■

RESULTS AND DISCUSSION The experimental data on the metastable solubilities and the physicochemical properties of the five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K are listed in Tables 2 and 3, respectively. The ion concentration values in 1687

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

Table 4. Pitzer Parameters of Electrolytes in the FiveComponent System (Li + Na + K + Cl + SO4 + H2O) at 298.15 K and 0.1 MPa electrolytes

β(0)

β(1)

C(Φ)

ref

LiCl NaCl KCl Li2SO4 Na2SO4 K2SO4

0.2082 0.0765 0.04835 0.1440 0.01958 0.04995

−0.07264 0.2664 0.2122 1.1774 1.1130 0.7793

−0.004241 0.001270 −0.0008400 −0.005710 0.004970 0.0

6 11 11 6 11 11

Table 5. Pitzer Mixing Parameters of the Five-Component System (Li + Na + K + Cl + SO4 + H2O) at 298.15 K and 0.1 MPa mixing parameters

θ

Li+, Na+ Li+, K+ Na+, K+ Cl−, SO42− Li+, Na+, Cl− Li+, Na+, SO42− Li+, K+, Cl− Li+, K+, SO42− Na+, K+, Cl− Na+, K+, SO42− Li+, Cl−, SO42− Na+, Cl−, SO42− K+, Cl−, SO42−

0.02016 −0.05075 −0.01200 0.02000

Ψ

ref

−0.007416 −0.007774 −0.005909 −0.007970 −0.001800 −0.01000 −0.01236 0.001400 0.0

6 11 11 11 6 6 6 6 11 11 6 11 11

Figure 2. Sodium-phase diagram of the metastable five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K and 0.1 MPa.

Figure 3. Water-phase diagram of the metastable five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K and 0.1 MPa.

LF (H + Syl + Ap), EF (H + Ap + Db3), KE (H + Ap + Th), GM (H + Ls + Lc), and GN (H + Syl + Lc), indicating the cosaturation of three salts. There are seven four-salt cosaturated invariant points of A, B, C, D, E, F, and G corresponding to Th + Db1 + Db3 + H, Db1 + Db2 + Db3 + H, Db2 + Db3 + Ls + H, Ls + Syl + Db3 + H, Th + Ap + Db3 + H, Ap + Syl + Db3 + H, and Ls + Syl + Lc + H, respectively. The crystallization zone of Db3 in the middle of the metastable phase diagram is the largest, and the crystallized zone area of lithium chloride monohydrate (LiCl·H2O, Lc) is the smallest. These results indicate that Db3 is easy to saturate and crystallize from solution, and lithium chloride has a high solubility during isothermal evaporation. Figures 2 and 3 show that Jänecke index

values of J(2Na+) and J(H2O) gradually decrease with increasing J(2Li+) for the strong salting-out effect of lithium chloride. On the basis of the physicochemical property data in Table 3, the relationship diagrams between the solution physicochemical properties (density, refractive index, conductivity, and pH) and the Jänecke index of J(2Li+) are shown in Figure 4. It can be seen that the physicochemical properties change regularly with the changes of Jänecke index of (2Li+). The study of metastable phase equilibrium of the fivecomponent system (Li + Na + K + Cl + SO4 + H2O) through

Figure 1. Metastable phase diagram saturated with NaCl for the five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K and 0.1 MPa. Th, Na2SO4; Syl, KCl; Ap, NaK3(SO4)2; Db1, Li2SO4·3Na2SO4·12H2O; Db2, Li2SO4·Na2SO4; Db3, 2Li2SO4·Na2SO4·K2SO4; Ls, Li2SO4·H2O; Lc, LiCl·H2O. 1688

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

Figure 4. Physicochemical properties versus composition diagram for the five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K and 0.1 MPa.

Table 6. μ0/RT Values of Species in the Five-Component System (Li + Na + K + Cl + SO4 + H2O) at 298.15 K and 0.1 MPa species H2O Li+ Na+ K+ Cl− SO42‑ NaK3(SO4)2 NaCl Na2SO4 KCl K2SO4 Li2SO4·H2O LiCl·H2O Li2SO4·3Na2SO4·12H2O Li2SO4·Na2SO4 2Li2SO4·Na2SO4·K2SO4 Li2SO4·K2SO4

abbr. of minerals

μ0/RT

ref

Ap H Th Syl Arc Ls Lc Db1 Db2 Db3 Db4

−95.6635 −118.0439 −105.651 −113.957 −52.955 −300.386 −1057.05 −154.99 −512.35 −164.84 −532.39 −631.1121 −254.5962 −3227.404 −1048.74 −2123.250 −1070.979

11 6 11 11 11 11 11 11 11 11 11 6 6 6 6 6 6

lithium resource. For the salt lake brines in the Qaidam Basin located in the Qinghai Plateau in China, the average temperature is 308.15 K during May to September, and the NaCl and KCl solid phases separate out first during the saline evaporation. Thus the composition of the brine lies in the KCl + NaCl crystallization zone of the metastable phase diagram in Figure 1. In the course of continuous evaporation of the brine, composition points of liquid phase are moving far from the KCl orthogonal vertex of Figure 1 and get to the equilibrium curve of H + Syl + Ap (KCl + NaCl + NaK3(SO4)2), and here the NaK3(SO4)2 solid phase crystallizes. Then composition points of liquid phase are moving to the cosaturated point F (KCl + NaCl + NaK3(SO4)2 + Db3) along with the above equilibrium curve. The brine is continuously evaporating at point F until NaK3(SO4)2 solid phase translates into double salt 3 (Db3) in whole. Afterward the composition point of liquid phase enters into the equilibrium curve of FD (KCl + NaCl + Db3). The lithium ions in the brine are enriched unceasingly during the above evaporating path.

■

PREDICTION OF SOLUBILITIES Ion-Interaction Model. Pitzer and co-workers have developed an ion interaction theory and published a series of papers,7−9 which gave a set of expressions for osmotic coefficients of the solution and mean activity coefficients of

simulating natural conditions is essential to guide the comprehensive exploitation and utilization of salt lake brine for an especial 1689

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

Figure 5. Comparison of the metastable and stable diagram saturated with NaCl for the five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K and 298.15 K and 0.1 MPa. Th, Na2SO4; Syl, KCl; Ap, NaK3(SO4)2; Db1, Li2SO4·3Na2SO4·12H2O; Db2, Li2SO4·Na2SO4; Db3, 2Li2SO4· Na2SO4·K2SO4; Ls, Li2SO4·H2O; Lc, LiCl·H2O.

Model Parameterization. Because the Pitzer parameters containing lithium and sodium such as θLi,Na, ΨLi,Na,Cl, and ΨLi,Na,SO4 are quite scarce at 308.15 K, the metastable solubilities of the five-component system (Li + Na + K + Cl + SO4 + H2O) cannot be calculated at 308.15 K. Nevertheless the Pitzer single-salt parameters, Pitzer mixing ion-interaction parameters, and μ0/RT values of the species in the five-component system at 298.15 K were reported and presented in Tables 4, 5, and 6,6,11 so the stable solubilities of the five-component system were calculated at 298.15 K. Calculated Solubilities. Using the chemical equilibrium HMW model and the above parameters, the calculated solubilities saturated with NaCl at 298.15 K were calculated with Fortran 77 programming on the basis of the digital visual Fortran Software 5.0, and the stable dry-salt phase diagram for the five-component system (Li + Na + K + Cl + SO4 + H2O) at 298.15 K was plotted in Figure 5 with solid lines, and the sodium and water phase diagrams were plotted in Figure 6. When compared with the metastable equilibrium phase diagram at 308.15 K, although the stable phase diagram obtained at 298.15 K has the same number of crystallization zones, the area of crystallization zones of Th (Na2SO4) and Db2 (Li2SO4·Na2SO4) are reduced obviously, and the area of other crystallization zones are enlarged obviously, while the equilibrium curve A′E′ (Na2SO4 + NaCl + 2Li2SO4·Na2SO4· K2SO4) is clearly shortened.

■

Figure 6. Calculated sodium and water phase diagrams saturated with NaCl for the five-component system (Li + Na + K + Cl + SO4 + H2O) at 298.15 K and 0.1 MPa. (a) Calculated sodium-phase diagram; (b) calculated water-phase diagram.

CONCLUSIONS Solubilities and physicochemical properties of the aqueous metastable equilibria of the reciprocal five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K were determined experimentally. According to the solubility data, the experimental metastable phase diagrams and the diagrams of physicochemical properties versus composition were plotted. On the basis of Pitzer’s ion interaction theory and the extended chemical equilibrium HMW model, the stable solubilities of the five-component system saturated with NaCl at 298.15 K were also calculated. Besides the different temperature, the differences between the stable and metastable phase diagrams of the five-component system mostly demonstrate that the metastable equilibrium on the basis of isothermal evaporation process of

electrolytes in the solution. Expressions of the chemical equilibrium HMW model for conventional single ion activity coefficients are more convenient to use in solubility calculations.10−17 Using the activity coefficients and the solubility products of the equilibrium solid phases allowed us to identify the solids existed and their compositions at equilibrium. Additional work was focused on developing variable-temperature models, which will increase the applicability to a number of diverse geochemical systems. The primary focus has been to broaden the models by generating parameters at higher or lower temperatures.23−25 1690

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691

Journal of Chemical & Engineering Data

Article

(16) Christov, C.; Møller, N. A chemical equilibrium model of solution behavior and solubility in the H + Na + K + Ca + OH + Cl + HSO4 + SO4 + H2O system to high concentration and temperature. Geochim. Cosmochim. Acta 2004, 68 (18), 3717−3739. (17) Eugster, H. P.; Harvie, C. E.; Weare, J. H. Mineral equilibria in a six-component seawater system Na + K + Mg + Ca + SO4 + Cl + H2O at 298.15 K. Geochim. Cosmochim. Acta 1980, 44, 1335−1347. (18) Felmy, A. R.; Weare, J. H. The prediction of borate mineral equilibria in nature waters: Application to Searles Lake, California. Geochim. Cosmochim. Acta 1986, 50, 2771−2783. (19) Guo, Y. F.; Yin, H. J.; Wu, X. H.; Deng, T. L. Metastable phase equilibrium in the aqueous quaternary system (NaCl + MgCl2 + Na2SO4 + MgSO4 + H2O) at 323.15 K. J. Chem. Eng. Data 2010, 55, 4215−4220. (20) Deng, T. L. Stable and metastable phase equilibria in the saltwater systems. In Advances in Crystallization Processes; Mastai, Y., Ed.; InTech Publisher: Croatia, 2012; Chapter 16, pp 399−430. (21) Deng, T. L.; Zhou, H.; Chen, X. Salt-water system phase diagrams and applications, Chemical Industry Press: Beijing, 2013; pp 203−217. (22) Analytical laboratory of Qinghai institute of salt lakes at CAS. The analyses of brines and salts, 2nd ed.; Science Press: Beijing, 1988; pp 35−41, 64−66. (23) Pabalan, R. T.; Pitzer, K. S. Thermodynamics of concentrated electrolyte mixtures and the prediction of mineral solubilities to high temperatures for mixtures in the system Na + K + Mg + Cl + SO4 + OH + H2O. Geochim. Cosmochim. Acta 1987, 51, 2429−2443. (24) Spencer, R. J.; Møller, N.; Weare, J. The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na + K + Ca + Mg + Cl + SO4 + H2O system at temperatures blow 25 °C. Geochim. Cosmochim. Acta 1990, 54, 575−590. (25) Greenberg, J. P.; Møller, N. The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na + K + Ca + Cl + SO4 + H2O system to high concentration from 0 °C to 250 °C. Geochim. Cosmochim. Acta 1989, 53, 2503−2518.

aqueous solution is more reasonable to guide the separation process of solar ponds.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Funding

The authors gratefully acknowledge partial financial supports from the State Key Program of NNSFC (Grant 20836009), the NNSFC (Grants. 21206136, 21267194, and 21306136), the Specialized Research Fund for the Doctoral Program of Chinese Higher Education (Grants 20101208110003 and 20111208110003), and the Key Pillar Program of Tianjin Municipal Science and Technology (11ZCKGX02800). Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Chen, J. Q.; Liu, Z. Q.; Fang, C. H. Studies on evaporationcrystallization of salt lake brines in China. J. Salt Lake Res. 1994, 2, 43− 51. (2) Jin, Z. M.; Xiao, X. Z.; Liang, S. M. Studies on the metastable phase equilibrium of (Na + K + Mg + Cl + SO4 + H2O) quinary system at 25°C. Acta Chim. Sin. 1980, 38 (4), 314−321. (3) Jin, Z. M.; Zhou, H. N.; Wang, L. S. Studies on the metastable phase equilibrium of (Na + K + Mg + Cl + SO4 + H2O) quinary system at 15°C. Chem. J. Chin. Univ. 2002, 23 (4), 690−694. (4) Fang, C. H.; Niu, Z. D.; Liu, Z. Q.; et al. Studies on the metastable phase diagram in the quinary system (Na + K + Cl + SO4 + CO3 + H2O) at 25 °C. Acta Chim. Sin. 1991, 49, 1062−1070. (5) Sang, S. H.; Yin, H. A.; Tang, M. L.; et al. (Liquid + solid) metastable equilibria in quinary system Li2CO3 + Na2CO3 + K2CO3 + Li2B4O7 + Na2B4O7 + K2B4O7 + H2O at T = 288 K for Zhabuye salt lake. J. Chem. Thermodyn. 2003, 35, 1513−1520. (6) Song, P. S.; Yao, Y. Thermodynamics and phase diagram of the salt lake brine system at 298.15 K. Calphad 2003, 27, 343−352. (7) Pitzer, K. S. Thermodynamics of electrolytes I: theoretical basis and general equation. J. Phys. Chem. 1973, 77, 268−277. (8) Pitzer, K. S. Activity coefficients in electrolyte solutions, 2nd ed.; CRC Press: London, 1992; pp 75−153. (9) Pitzer, K. S. Semi-empirical equations for pure and mixed electrolytes. In Thermodynamics, 3rd ed.; Pitzer, K. S., Ed.; McGrawHill, Inc.: New York, 1995; Chapter 17, pp 290−321. (10) Harvie, C. E.; Weare, J. H. The prediction of mineral solubilties in nature waters: the Na + K + Mg + Cl + SO4 + H2O system from zero to high concentration at 25 °C. Geochim. Cosmochim. Acta 1980, 44, 981−997. (11) Harvie, C. E.; Møller, N.; Weare, J. H. The prediction of mineral solubilities in nature waters: the Na + K + Mg + Ca + H + SO4 + OH + HCO3 + CO3 + H2O system to high ionic strengths at 25 °C. Geochim. Cosmochim. Acta 1984, 48, 723−751. (12) Christov, C.; Møller, N. Chemical equilibrium model of solution behavior and solubility in the H + Na + K + OH + Cl + HSO4 + SO4 + H2O system to high concentration and temperature. Geochim. Cosmochim. Acta 2004, 68, 1309−1331. (13) Møller, N. The prediction of mineral solubilities in natural waters: a chemical equilibrium model for the Na + Ca + Cl + SO4 + H2O system to high temperature and concentration. Geochim. Cosmochim. Acta 1988, 52, 821−837. (14) Greenberg, J.; Møller, N. The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na + K + Ca + Cl + SO4 + H2O system to high concentration from 0 to 250 °C. Geochim. Cosmochim. Acta 1989, 53, 2503−2518. (15) Møller, N.; Greenberg, J.; Weare, J. Computer modeling for geothermal systems: predicting carbonate and silica scale formation, CO2 breakout and H2S exchange. Transport Porous Med. 1988, 33, 173−204. 1691

dx.doi.org/10.1021/je500140e | J. Chem. Eng. Data 2014, 59, 1685−1691