Stable Phase Equilibrium of the Quaternary System Li 2 SO 4 + Cs 2 SO 4 + MgSO 4 + H 2 O at 298.2 K

et al. 2019

J. Chem. Eng. Data

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The stable equilibrium solubility, density, and refractive index of the quaternary system Li+, Na+, Mg2+//SO4 2––H2O were studied at T = 323 K by the isothermal dissolution method. The results show that at T = 323 K, a sodium–magnesium sulfate mineral astrakhanite (Na2SO4·MgSO4·4H2O) and a lithium–sodium sulfate double salt (Li2SO4·Na2SO4) are formed in this quaternary system 323 K, but no double salt or solid solution formed between lithium sulfate and magnesium sulfate. The phase diagram consists of seven isothermal dissolution curves, five regions of crystallization, and three invariant points, among which one belongs to an commensurate point (H3) and two belong to incommensurate points (H1 and H2). Its five crystallization fields correspond to single salts Li2SO4·H2O, Na2SO4, hexahydrite (MgSO4·6H2O), and two double salts astrakhanite (Na2SO4·MgSO4·4H2O) and Li2SO4·Na2SO4. Hexahydrite (MgSO4·6H2O) has the smallest crystal phase region, while lithium sulfate monohydrate (Li2SO4·H2O) has the largest crystal region. At equilibrium, the refractive index and density in the solution change regularly with the change in concentration of sodium sulfate. Comparisons of the phase diagrams of Li+, Na+, Mg2+//SO4 2––H2O at different temperatures show that the temperature is the main factor for the salt crystals, not only the crystallization form but also the crystal water content.

Section: Introductionmentioning

confidence: 99%

Stable Phase Diagram of the Quaternary Water–Salt System Li⁺, Na⁺, Mg²⁺//SO₄^2––H₂O at T = 323 K

Zuo

et al. 2019

J. Chem. Eng. Data

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“…The ternary system Li + , Mg 2+ //SO 4 2– –H 2 O at 273.2, 288.15, 298.2, and 308.15 K demonstrated that a simple system is likely been formed rather than a double system. − The research on the phase equilibrium of the ternary system Li + , Rb + //SO 4 2– –H 2 O 298 K has been reported in many articles in the 20th century. − Some scholars have studied the quaternary systems Li + , K + , Rb + //SO 4 2– –H 2 O, Li + , Na + , Rb + //SO 4 2– –H 2 O. Our research group has also completed the following research work: ternary system Li + , Rb + //SO 4 2– –H 2 O at 298.2 K, Rb + , Mg 2+ //SO 4 2– –H 2 O at 298.2 K, , quaternary system Rb + , Cs + , Mg 2+ //SO 4 2– –H 2 O at 298.2 K, and Li + , Cs + , Mg 2+ //SO 4 2– –H 2 O at 298.2 K. , Owing to the low annual average temperature(near 0 degrees) in the Qaidam Basin, it is necessary to determine a stable phase equilibrium of the sulfate system with lithium, rubidium, and magnesium coexistence at 273.2 K, which has not been reported yet. The isothermal dissolution method was used in this work to carry out a study on the phase equilibrium of the quaternary system Li + , Rb + , Mg 2+ //SO 4 2– –H 2 O at 273.2 K. It provides solubility data for the separation and extraction of lithium and rubidium resources in brine.…”

Section: Introductionmentioning

confidence: 99%

Stable Phase Equilibria of the Quaternary Water–Salt System Li⁺, Rb⁺, Mg²⁺//SO₄^2––H₂O at T = 273.2 K

Wang

et al. 2023

ACS Omega

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The phase equilibria for the quaternary system Li + , Rb + , Mg 2+ // SO 4 2− − H 2 O at 273.2 K were studied by the isothermal dissolution equilibrium method. Based on the measured data, the space diagram, stable phase diagram, water content diagram, and the diagram of density vs composition are plotted. The stable phase diagram in the system consists of four quaternary invariant points, nine univariate curves, and six crystallization zones. For the invariant points, E 1 and E 4 belong to the commensurate type, and E 2 and E 3 belong to the incommensurate type. The order of the crystallization area is RbThe density of the equilibrium liquid changed regularly with the content of Rb 2 SO 4 in the solution. By comparing the stable phase diagram of the partial ternary subsystems at T = 273.2 K and T = 298.2 K, it is found that the crystallization regions of Rb 2 SO 4 increases with the decrease in temperature, which indicates that cooling is conducive to the crystallization of Rb 2 SO 4 . By comparing the stable phase diagram of the system at T = 273.2 K and T = 308.2 K, it was found that the system was composed of four invariant points, nine univariate curves, and six crystal regions. The double salt 3Li 2 SO 4 •Rb 2 SO 4 •2H 2 O is converted to 3Li 2 SO 4 •Rb 2 SO 4 . The crystallization region of single salt MgSO 4 •7H 2 O, Rb 2 SO 4 and double salt Li 2 SO 4 •Rb 2 SO 4 decreased obviously.

“…Besides, there is a larger crystallization area for these double salts in the corresponding system. With the increase of temperature, the systems (Li + , Cs + , Mg 2+ //SO 4 2– –H 2 O) and (Li + , Na + , Cs + //SO 4 2– –H 2 O) form the double salts Li 2 SO 4 ·Cs 2 SO 4 and 3Li 2 SO 4 ·Cs 2 SO 4 ·2H 2 O at 298.2 K, making it impossible to extract the pure salt lithium sulfate from the system directly. Perhaps lithium can be isolated and purified after precipitation from brine in the form of lithium double salt.…”

Section: Introductionmentioning

confidence: 99%

Solid–Liquid Phase Diagram of the Quinary Water–Salt System Li⁺, Na⁺, Rb⁺, Mg²⁺//SO₄^2––H₂O at T = 298.2 K

Zuo

et al. 2023

J. Chem. Eng. Data

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Lithium, rubidium, and magnesium are the elements with high development value found in the salt lake in the Qaidam Basin. The isothermal dissolution method was used to study the solid–liquid phase diagram of the quinary system Li+, Na+, Rb+, Mg2+//SO4 2––H2O at T = 298.2 K to develop and utilize valuable components in salt lakes and enrich thermodynamic data. Based on the experimental data, a series of diagrams were created. The results indicate that its space diagram consists of 9 crystalline regions, 21 isothermal dissolution curves, and 7 four-salt cosaturation invariant points at T = 298.2 K. The quinary system (Li+, Na+, Rb+, Mg2+//SO4 2––H2O at T = 298.2 K) produced five different double salts (3Na2SO4·Li2SO4·12H2O, Li2SO4·Rb2SO4, 3Li2SO4·Rb2SO4·2H2O, Rb2SO4·MgSO4·6H2O, and Na2SO4·MgSO4·4H2O); however, no double salt is created when lithium and magnesium or sodium and rubidium interact. The crystal area of the double salt Rb2SO4·MgSO4·6H2O is the greatest in the phase diagram of sodium sulfate saturation, while the crystal area of Li2SO4·H2O is the smallest in the phase diagram of magnesium sulfate saturation. The article concentrates on lithium loss during recovery. The experimental data and research can guide the efficient separation and utilization of lithium and rubidium in the bittern industry.