Dry-salt Phase Diagram Research Articles

Solid–Liquid Phase Equilibria of the Quaternary System NaCl–CaCl2–H3BO3–H2O at 323.15 K: Solubility Determination and Thermodynamic Model

The solid–liquid phase equilibria of brine systems containing boric acid are the theoretical basis for the development of boric acid from brine resources. The phase equilibria of the systems NaCl–CaCl2–H3BO3–H2O and CaCl2–H3BO3–H2O at 323.15 K were investigated by the isothermal solution method. The phase diagram for the ternary system is composed of one co-saturation point, two univariant solubility curves, and two singe-salt crystallization fields of CaCl2·2H2O and H3BO3. The dry-salt phase diagram for the quaternary system consists of one invariant point, three univariant solubility curves, and three single-salt crystallization fields for NaCl, CaCl2·2H2O, and H3BO3. In the phase diagrams of the quaternary system at 298.15 and 323.15 K, the areas of sodium chloride and calcium chloride salt regions are enlarged, whereas the area of the H3BO3 region is diminished significantly with the increase of temperature. Using the Pitzer model, the lacking Pitzer parameters for H3BO3 were obtained by fitting the solubilities in the CaCl2–H3BO3–H2O system. The calculated solubilities with the Pitzer model were in accord with the experimental data.

Solid–Liquid Phase Equilibria in the Quinary System NaCl-KCl-MgCl2-SrCl2-H2O at 273 K

To realize the comprehensive utilization of underground brines, this work focuses on the research of phase equilibria in salt–water systems containing potassium, sodium, magnesium, strontium, and chlorine. The solid–liquid phase equilibria in the quinary system NaCl-KCl-MgCl2-SrCl2-H2O at 273 K were determined by the isothermal dissolution equilibrium method. X-ray powder diffraction was used to identify the equilibrium solids in invariant points, and the XRD diffraction patterns of equilibrium solids in invariant points were obtained. Based on the experimental data, the three-dimensional equilibrium phase diagram was constructed. The results show that no solid solution is formed in the quinary system, while the double salt KCl·MgCl2·6H2O and corresponding hydrates SrCl2·6H2O and MgCl2·6H2O are formed. The three-dimensional equilibrium phase diagram of this quinary system at 273 K contains two invariant points, seven isothermal solubility curves, and five single salt crystallization regions corresponding to NaCl, KCl, MgCl2·6H2O, SrCl2·6H2O, and KCl·MgCl2·6H2O. In addition, two-dimensional projection phase diagrams with the saturated surfaces of NaCl, KCl, and SrCl2·6H2O were also analyzed, and the dry-salt phase diagrams were also obtained. When NaCl is saturated, there are two invariant points, five univariant curves, and four crystallization regions (KCl, MgCl2·6H2O, SrCl2·6H2O, and KCl·MgCl2·6H2O) in the dry-salt phase diagram. When KCl is saturated, the dry-salt phase diagram consists of only one invariant point, three univariant curves, and three crystallization regions (NaCl, SrCl2·6H2O, and KCl·MgCl2·6H2O). When SrCl2·6H2O is saturated, the dry-salt phase diagram contains two invariant points, five univariant curves, and four crystallization regions corresponding to NaCl, KCl, MgCl2·6H2O, and KCl·MgCl2·6H2O.

Solid-Liquid Phase Equilibria of the Quaternary System (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K: Experimental and Theoretical Prediction

The isothermal dissolution equilibrium method was employed to obtain the solubilities and physicochemical properties of the quaternary system (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K in this work. The dry-salt phase diagram, water-phase diagram, and physicochemical properties, including density, refractive index, and pH against composition in the quaternary system, were established for the first time. The dry-salt phase diagram includes two invariant points, five univariate solubility curves, and four single salt crystalline phase regions (LiCl·H2O, LiBO2·2H2O, LiBO2·8H2O and Li2B4O7·3H2O), respectively. In addition, the physicochemical properties of density, refractive index, and pH in the system change regularly with the changing of the lithium metaborate concentration. Based on the Pitzer model, the mixing ion parameters of θCl,B4O5(OH)4, θB(OH)4,B4O5(OH)4 and Ψ(Li,Cl,B4O5(OH)4, ΨLi,B (OH)4,B4O5(OH)4 and the predictive solubilities in the quaternary system were fitted. Although there is a slight deviation between the calculated and experimental values, the solubility of boron in the quaternary system agrees well, which provides data support for the study of the solubility of boron.

Stable phase equilibria in the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 288 K

Sichuan Basin is rich in underground brines, which are important liquid mineral resources. In order to realize the exploitation and utilization of the brine resources, in this work, we used the isothermal dissolution equilibria method to study the phase equilibria of related subsystem for the underground brines. Consequently, the phase equilibria of the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 288 K are studied in detail. The solubilities of salts in saturated liquid phase of the quinary system were measured by chemical analysis, and the equilibrium solid phases of the quinary system were identified by chemical analysis and X-ray powder diffraction. The phase diagrams of the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 288 K were also given, and simplified dry base salt diagram, water content diagram and saturated salt content diagram of each salt saturation surface were presented respectively. The results show that the quinary system is a hydrate type. When LiCl, NaCl, KCl and SrCl2 are saturated respectively, the dry salt phase diagrams have different crystalline regions. When LiCl·2H2O is saturated, the crystalline regions are SrCl2·2H2O, NaCl and KCl; When NaCl is saturated, the crystalline regions are KCl, SrCl2·6H2O, SrCl2·2H2O and LiCl·2H2O; When KCl is saturated, the crystalline regions are NaCl, SrCl2·6H2O, SrCl2·2H2O and LiCl·2H2O; When SrCl2·6H2O is saturated, the crystalline regions are KCl, NaCl and SrCl2·2H2O.

Solid-liquid phase equilibria of the quinary system containing sodium, potassium, lithium, chloride and pentaborate ions at 298.15 K and 101.325 kPa

The solid–liquid phase equilibria of the quinary system (Li+, Na+, K+//Cl−, B5O8− - H2O) saturated with NaCl at 298.15 K and 101.325 kPa were investigated with the isothermal dissolution method. On the basis of experimental data, the dry-salt phase diagram, water-phase diagram and sodium-phase diagram in the quinary system were established for the first time. In this quinary dry-salt phase diagram, there are three invariant points corresponding to F1 (NaCl + KCl + LiCl·H2O + LiB5O8·5H2O), F2 (NaCl + KCl + LiB5O8·5H2O + KB5O8·4H2O) and F3 (NaCl + LiB5O8·5H2O + NaB5O8·5H2O + KB5O8·4H2O), seven isothermal dissolution curves, and five crystallization regions saturated with NaCl corresponding to LiCl·H2O, KCl, LiB5O8·5H2O, NaB5O8·5H2O, KB5O8·4H2O. The areas of crystallized regions decrease according to the order of NaB5O8·5H2O, KB5O8·4H2O, LiB5O8·5H2O, KCl, and LiCl·H2O, which all are saturated with sodium chloride. It was found that neither double salt nor solid solution was formed. In addition, the diagram of physicochemical properties including densities and refractive indices against J(B5O8−) was also established, and it shows that density and refractive index of the solution in the quinary system change regularly with the increasing of Jänecke index J(B5O8−) in the solution. These results on the phase diagram of the quinary system can supply a theoretical guide to separate and purify the valuable alkali pentaborates.

Solubility determination and thermodynamic modelling of solid-liquid equilibria in the (NaCl + NaBO2 + Na2B4O7 + H2O) system at 298.15 K

The solubility corresponding solution physicochemical properties (densities, refractive indices and pH) in the quaternary system (NaCl + NaBO2 + Na2B4O7 + H2O) were investigated at 298.15 K by the isothermal dissolution equilibrium method. The dry-salt phase diagram, water content diagram, refractive index diagram and pH diagram were drawn. There are four crystallization fields corresponding to NaCl, NaBO2·4H2O, Na2B4O7·10H2O, NaCl·NaBO2·2H2O, five univariant curves and two invariant points in the phase diagram of the quaternary system. The solubility, concentrations of boron species B(OH)3, B(OH)4−, B3O3(OH)4−, B4O5(OH)42− and OH− in the system were calculated using the Pitzer model. The variation trends for calculated solubility curves and pH curves are consistent with the experimental results. The distributions of different boron species were obtained in the mixed borate solution. The distributions of four boron species were obtained in the mixed borate solution. The main boron species in the mixed borate solution are B(OH)4− and B4O5(OH)42−. The mole fractions of the four boron species are mainly affected by m(B) in the solution but less by m(Cl−).

Phase equilibria in the sea-water Na, K, Mg//Cl, SO4–H2O quinary system at 0 °C

The phase equilibria in the quinary Na, K, Mg//Cl, SO4–H2O sea-water system at 0 °C were determined and a total phase equilibria diagram for the system was constructed by means of the translation method consistent with available literature data. There are seven points, 21 curves and 22 fields saturated, respectively, with 4, 3 and 2 equilibrium solid phases, for the quinary composition of the system. The constructed total phase equilibria diagram of the system was fragmented into divariant co-crystallization fields of two different solid phases and trivariant crystallization volumes of each of the solid phases at equilibrium. The structures of nine Janecke dry-salt phase diagrams were obtained by fragmentation of the total phase equilibria diagram into crystallization volumes. The comparison with the available literature data shows that, the obtained crystallization volume for halite agrees well with the available experimental data.

Solid–Liquid Phase Equilibria of the Quaternary System MgCl2–PbCl2–ZnCl2–H2O at 323 K

To provide theoretical data for the hydrometallurgical process of lead–zinc ores and the separation process of secondary lead recovery, the quaternary system MgCl2–PbCl2–ZnCl2–H2O at 323 K was investigated using the isothermal dissolution equilibrium method. The isothermal solubility data were obtained, based on which the corresponding dry salt phase diagram and the water content diagram were constructed. The double salts MgZnCl4·6H2O and 3MgCl2·2PbCl2·18H2O were found in the equilibrium solid phases as its ternary subsystems. The dry salt phase diagram contains three invariant points, seven isothermal solubility curves, and five crystallization fields (the crystal salts are PbCl2, 3MgCl2·2PbCl2·18H2O, ZnCl2, MgZnCl4·6H2O, and MgCl2·6H2O(Bis), respectively), and the crystallization region of PbCl2 is the largest. At the same time, the invariant data of this quaternary system and its ternary subsystems at different temperatures were compared and discussed.

Solid–Liquid Phase Equilibria of the Quaternary System (Li2B4O7 + Na2B4O7 + K2B4O7 + H2O) at 323.15 K and Its Application in Industry

The solubilities and refractive indices of the quaternary system (Li2B4O7 + Na2B4O7 + K2B4O7 + H2O) were attained at 323.15 K by the isothermal dissolution equilibrium method. The dry-salt phase diagram, water content diagram and refractive index diagram were plotted. The phase diagram contains three univariant curves, three crystallization fields (Li2B4O7·3H2O, Na2B4O7·10H2O, K2B4O7·4H2O), and one invariant point. The system is a simple quaternary solid–liquid equilibrium type without double salt or solid solution. A comparison of the phase diagram of the quaternary system at 288.15 and 323.15 K shows that the crystallization regions of Li2B4O7·3H2O becomes larger with the increasing of temperature. The refractive indices calculated with semiempirical formula are in good agreement with the experimental results. The brine separation process was demonstrated with the phase diagrams at 288.15 and 323.15 K. All Li2B4O7·3H2O, most of Na2B4O7·10H2O, and K2B4O7·4H2O can be separated from the solution with the phase diagrams at 288.15 and 323.15 K.

Solid-Liquid Phase Equilibria in the Quinary System NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K.

Solid–liquid equilibria in the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were measured by the wet residue method, and the equilibrium solid phases and solubilities of saturated solutions were determined experimentally. Using the experimental results, dry-salt phase diagrams and water diagrams versus composition diagrams were plotted (saturated with saturated sodium chloride, sodium hydroxide, sodium carbonate, and sodium sulfate). The experimental results show that there are a solid solution (γ-salt, mNa2SO4·nNa2CO3) and co-saturation complex salts (S3, Na2SO4·NaCl·NaOH and S1, NaOH·Na2SO4) formed in this quinary system. Based on Xu’s activity coefficient model, the solubilities of the quinary system NaCl + NaOH + Na2CO3 + Na2SO4 + H2O at 363.15 K were calculated with corresponding parameters. Comparing the experimental and calculated results, it was shown that the calculated values had a good agreement with the experimental ones.

Stable phase equilibrium of the quaternary system NaCl-MgCl2-NH4Cl-H2O at 348.15 K and its application in industry

Based on the requirement of the new technology to achieve comprehensive utilization of sodium and magnesium resources by using the mother solution from the preparation of potassium salt as raw material, the phase equilibrium data of the quaternary system NH4Cl-MgCl2-NaCl-H2O as well as its ternary subsystems MgCl2-NH4Cl-H2O and NaCl-NH4Cl-H2O were investigated by an isothermal equilibrium method under atmospheric pressure at 348.15 K, and the dry-salt phase diagram and water-phase diagram were drawn. Two invariant points and four crystallization fields including two single salts NH4Cl and NaCl, one hydrate salt MgCl2·6H2O, and one double salt MgCl2·NH4Cl·6H2O were determined in this quaternary system. Combining our results with available experimental data in the literature, an optimized process to produce ammonium carnallite and NaCl was proposed. Using the Pitzer electrolyte solution model, the experimental results were regressed and calculated. The calculated values agree well with the experimental values.

Solid-liquid phase equilibria of quaternary systems Na+//Cl−, CO32−, SO42− - H2O and Na+//Cl−, CO32−, NO3− - H2O at T = 313.15 K

The solid-liquid equilibrium of quaternary systems (Na+//Cl−, CO32−, NO3− -H2O) and (Na+//Cl−, CO32−, SO42− -H2O) at 313.15 K was studied by an isothermal solution saturation method and the solubility of salts and equilibrium solid phases in the two systems was determined. The solid phases formed in the systems studied were determined by the Schreinemaker wet residue method. Based on the measured data, dry-salt phase diagrams and the relevant water-phase diagrams were plotted in the two systems. The stable phase diagram of Na+//Cl−, CO32−, NO3− -H2O at 313.15 K is characterized by one quaternary invariant point (Q), three univariant curves, and three crystallographic forms (corresponding to NaCl, NaNO3 and Na2CO3·H2O). The crystallization region of NaNO3 (I) is the smallest, and its solubility is the greatest, which indicates that NaNO3 has a strong salt-out effect on Na2CO3·H2O and NaCl. The composition of the solution at equilibrium corresponding to invariant point is w(NaCl) = 9.76 wt%, w(NaNO3) = 32.79 wt%, w(Na2CO3) = 6.10 wt%. Therefore, it can be considered that there is no double salt and solid solution in the quaternary system, which belongs to the simple quaternary system. For the quaternary systems (Na+//Cl−, CO32−, SO42− -H2O) at 313.15 K, experimental results indicate that there are four crystallographic forms (NaCl, Na2CO3·H2O, Na2SO4 and Bur (2Na2SO4 Na2CO3)), five univariant curves, and two invariant points corresponding to three salts, that is (NaCl + Na2SO4 + 2Na2SO4 Na2CO3) and (NaCl + Na2CO3·H2O + 2Na2SO4 Na2CO3), respectively. The experimental results show that this system is a complex eutectic type, and no solid solutions are found at the investigated temperature. All the physical properties (ρ, η, nD) of the equilibrium two quaternary systems change regularly with concentration change of the liquid phase. The phase equilibria in the quinary Na+//C1−, SO42−, CO32−, NO3−-H2O system at 313.15 K were also studied using the through and intermediate translation techniques together. All data and results obtained in this paper are of great significance to the design and optimization of the fractional crystallization process of the high-saline wastewater in coal chemical industry.

Phase Equilibria of the Reciprocal Quaternary System (Na+, Ca2+//Cl–, Borate–H2O) at 288.15 K and 0.1 MPa

To exploit the valuable features of brine resources with high concentrations of borate ions, the solubility data and corresponding physicochemical properties (refractive index, density, viscosity, and pH) for the reciprocal quaternary system (Na+, Ca2+//Cl–, borate–H2O) at 288.15 K were determined experimentally using the method of isothermal dissolution equilibrium. The dry-salt and water-phase diagrams and the diagrams of physicochemical properties (refractive index, density, viscosity, and pH) against J(B4O72–) in the solution were established. In the dry-salt phase diagram of the quaternary system at 288.15 K, two invariant points, five univariant curves, and four crystallization regions corresponding to gowerite (CaB6O10·5H2O), borax (Na2B4O7·10H2O), antarcticite (CaCl2·6H2O), and sodium chloride (NaCl) were found. The area of crystallization region of CaB6O10·5H2O is larger than that of other coexisting salts, which indicates that the solubility of gowerite in this system is the lowest and that it i...

Metastable Phase Equilibrium of the Quaternary System Na+, Rb+, Mg2+//Cl–-H2O at 298.2 K

The component solubilities, densities and refractive indices of the quaternary system Na+, Rb+, Mg2+//Cl–-H2O at 298.2 K were measured using an isothermal evaporation method. Based on the gathered data, a metastable phase diagram, a water content diagram, and a density/refractive index vs. composition diagram were constructed. The results show that this system is of a complex type with a double salt rubidium carnallite (RbCl·MgCl2·6H2O) formed at 298.2 K. Double salt rubidium carnallite, whose component point locates in its own crystallization zone in the dry salt phase diagram, belongs to congruent double salt at 298.2 K. Accompanied by the double salt that was formed, there are two invariant points in the phase diagram that cosaturated with three salts and an equilibrated solution. The cosaturated salts for the two invariant points are MgCl2·6H2O+RbCl·MgCl2·6H2O+ NaCl and NaCl+RbCl+RbCl·MgCl2·6H2O, respectively. Both invariant points are commensurate invariant points in the evaporation process, and the two invariant points are evaporative dry points. The sizes of the crystalline regions of the salts are in the order of NaCl>RbCl>RbCl·MgCl2·6H2O>MgCl2·6H2O.

Metastable Phase Equilibrium in the Reciprocal Quaternary System LiCl+MgCl2+Li2SO4+MgSO4+H2O at 348.15 K and 0.1 MPa

The metastable solubilities and the physicochemical properties including density and pH of the reciprocal quaternary system(LiCl+MgCl2+Li2SO4+MgSO4+H2O) at 348.15 K and 0.1 MPa were determined using the isother-mal evaporation method. The dry-salt diagram and water-phase diagram were plotted based on the experimental data. There are five invariant points, eleven univariant curves, and seven crystallization zones corresponding to hexahy-drite, tetrahydrite, kieserite, bischofite, lithium sulfate monohydrate, lithium chloride monohydrate and lithium car-nallite. Comparison between the stable and metastable diagrams at 348.15 K indicates that the metastable phenome-non of magnesium sulfate is obvious, and the crystallization regions of hexahydrite and tetrahydrite disappear in the stable phase diagram. A comparison of the metastable dry-salt phase diagrams at 308.15, 323.15 and 348.15 K shows that with the increasing of temperature the epsomite crystallization zone disappears from the dry-salt phase diagram of 303.15 K, and a new kieserite crystallization zone is presented at 348.15 K. The density and pH in the metastable equilibrium solution present regular change with the increasing of Janecke index J(2Li+), and the calculated densities using the empirical equation agree well with the experimental values.

Investigation of Phase Equilibria in Quinary Water–Salt Systems

Isothermal methods of investigation of quinary systems and advantages of use of the translation method for investigation of quinary water–salt systems were discussed. Two quinary systems—Li, Na, K//CO3, B4O7–H2O and Na, K//Br, SO4, B4O7–H2O—were investigated by means of the translation method at 15 and 25 °C, respectively. The comparison showed a good agreement between our results and the available literature data. There are 4 points, 13 curves, and 15 fields saturated with 4, 3, and 2 different equilibrium solid phases, respectively, in Li, Na, K//CO3, B4O7–H2O systems at 15 °C. The quinary Na, K//Br, SO4, B4O7–H2O system at 25 °C involves 5 invariant points, 16 monovariant curves, and 18 divariant fields saturated with 4, 3, and 2 different equilibrium solid phases, respectively. The total phase equilibria diagrams of both of the quinary systems were constructed on the basis of obtained data. The obtained diagrams were fragmented into divariant cocrystallization fields saturated with two different equilibrium solid phases. The trivariant crystallization volumes, which reflect the structures of Jänecke dry-salt phase diagrams of the systems saturated with the relevant phases, were also extracted.

Solid–Liquid Equilibria in the Quaternary System Na+,K+//HPO42–,Cl––H2O and Its Subsystems Na+//HPO42–,Cl––H2O, K+//HPO42–,Cl––H2O, and Na+,K+//HPO42––H2O at 298.2 K

The solid–liquid equilibrium of the quaternary system Na+,K+//HPO42–,Cl––H2O and its subsystems Na+//HPO42–,Cl––H2O, Na+, K+//HPO42–,Cl––H2O, Na+,K+//HPO42––H2O at 298.2K were investigated by the isothermal solution saturation method. The solubility of salts and the equilibrium solid phases were determined. The ternary phase diagram, quaternary dry-salt phase diagram, and the water-content diagram were constructed. There is one invariant point, two univariant curves, and four crystallization regions in the ternary system Na+//HPO42–,Cl– −H2O and K+//HPO42–,Cl––H2O. The ternary system Na+,K+//HPO42––H2O contains two invariant points, three univariant curves, and six crystallization regions. The quaternary system Na+,K+//HPO42–,Cl––H2O contains three invariant points, seven univariant curves, and five crystallization regions corresponding to KCl, NaCl, Na2HPO4·12H2O, Na2HPO4·7H2O, and K2HPO4·3H2O. In the quaternary system, KCl occupies the largest crystallization region while K2HPO4·3H2O crystallization region is the smallest. Three kinds of hydrated salts were found in the system while there is no double salts or solid solution. HPO42– is the main factor that affects the relative water content in the liquid phase. All the data and results obtained in this paper are of great significance to the crystallization technology of K2HPO4 and the new production process of KH2PO4.

Solid and liquid metastable phase equilibria in the aqueous quaternary system Li+, Mg2+//SO4 2–, borate-H2O at 273.15 K

The metastable phase equilibria of the Li+, Mg2+//SO4 2–, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical property diagrams of the system were plotted with the metastable solubility values and physicochemical properties corresponding to density, refractive index, pH value and conductivity. The dry-salt diagram was composed of four crystallizing zones[lithium sulfate hydrate(Li2SO4·H2O), epsomite(MgSO4·7H2O), lithium metaborate octahydrate(LiBO2·8H2O), and hungchaoite(MgB4O7·9H2O)], five univariant curves and two invariant points (Li2SO4·H2O+MgSO4·7H2O+MgB4O7·9H2O and Li2SO4·H2O+LiBO2·8H2O+MgB4O7·9H2O). Li2B4O7 converted into LiBO2 in solution. Comparing the metastable phase diagram at 273.15 K and stable phase diagram at 298.15 K for the system, the crystallized area of Li2SO4·H2O and MgSO4·7H2O became large, whereas, the other phase regions became small. The J(H2O) changes regularly with increasing J(SO4 2‒), and the physicochemical properties change regularly with the concentration of B4O7 2‒ increasing.

Solid-liquid equilibrium of Na+//Cl−, NO3−, SO42− -H2O quaternary system at 373.15 K

Solid-liquid equilibrium (SLE) of Na+//Cl−, NO3−, SO42− -H2O quaternary system at 373.15 K was determined via isothermal solubility equilibrium method. The dry-salt phase diagram and the tri-prism stereogram of this system were obtained found on the solubility data. Without any solid solutions or double salts, the phase diagram is the simplest one of the quaternary system, consisting of one invariant point, three univariant curves, three crystallization fields of single salts, three cocrystallization fields for two salts and one cocrystallization field for three salts. At the same time, the physicochemical properties (density and conductivity) of this system were measured in the experiment. Moreover, comparing with the equilibrium phase diagrams in the temperature range from 258.15 K to 373.15 K, it could be found that the crystallization field of the double salt D (NaNO3.Na2SO4.10H2O) reduces with the temperature increases, and disappears at 373.15 K. With the growing temperature, the crystallization field of Na2SO4 enlarges while the crystallization fields of NaNO3 and NaCl both reduce. All above the experimental results obtained can be applied to solve the salt separation of the relative brine system mainly containing the four aforementioned ions as well as conduct further theoretical studies.

Solubilities, Densities and Refractive Indices in the Aqueous Quaternary System of Lithium Sulfate, Lithium Metaborate, and Lithium Carbonate at 288.15, 298.15, 308.15 K and 0.1 MPa

Solubilities, densities and refractive indices of the aqueous quaternary system of lithium sulfate, lithium metaborate, and lithium carbonate at 288.15, 298.15, 308.15 K and 0.1 MPa were determined with isothermal dissolution method. According to the experimental results, the dry-salt phase diagrams, water-phase diagrams, and the diagrams of physicochemical properties including density, pH, and refractive index versus composition of lithium sulfate at three temperatures were plotted. In the dry-salt phase diagrams at three temperatures, there are four crystallization regions corresponding to lithium metaborate octahydrate (LiBO2·8H2O, LB), lithium carbonate (Li2CO3, LC), and lithium sulfate monohydrate (Li2SO4·H2O, LS), and three univariant-solubility curves corresponding to minerals of LS, LB, and LC, and one invariant point of three coexisted minerals (LS + LB + LC). A comparison of the phase diagrams at 288.15, 298.15, and 308.15 K shows that the areas of lithium sulfate monohydrate and lithium metabor...