Experimental and Thermodynamic Modeling Study of the Quaternary System Containing Lithium, Potassium, Magnesium, and Sulfate at 288.15 K

Abstract

Solid–liquid phase equilibria of the quaternary system (Li + K + Mg + SO4 + H2O) at 288.15 K were investigated with the isothermal dissolution method. The diagrams of solubilities, densities and refractive indices were plotted, respectively. The solubilities diagram of the quaternary system includes three invariant points cosaturated with three salts and five crystallization zones. Two kinds of double salts K2SO4·MgSO4·6H2O and Li2SO4·K2SO4 were found, and no solid solution was formed. Pitzer theory for aqueous electrolyte solution and its extended Harvie-Møller-Weare (HMW) model was used to calculate the solubilities of the quaternary system. A comparison between the calculated and the experimental results shows that the predicted solubilities obtained with the extended HMW model agree well with experimental data.

Stable Phase Equilibria of the Quaternary Water–Salt System Li+, Rb+, Mg2+//SO42––H2O at T = 273.2 K

“…A lot of studies had been done in the water–salt system containing lithium or rubidium. 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.…”