Phase Equilibria for the Aqueous Quinary System Li+, Na+, K+, Mg2+//Cl––H2O Saturated with NaCl·2H2O at 258.15 K

Abstract

The phase diagram can guide the comprehensive utilization of salt lake brine, particularly lithium extraction. In this paper, the study on phase equilibria of the quinary system Li+, Na+, K+, Mg2+//Cl––H2O saturated with NaCl·2H2O and its subsystem Li+, Na+, Mg2+//Cl––H2O at 258.15 K were carried out using the isothermal dissolution equilibrium method. Based on the experimental data, equilibrium diagrams for stable phases were plotted. For the equilibrium diagram of the quaternary system Li+, Na+, Mg2+//Cl––H2O at 258.15 K, there are two invariant points, five univariant curves, and four crystallization fields. The quinary system Li+, Na+, K+, Mg2+//Cl––H2O saturated with NaCl·2H2O at 258.15 K contains three invariant points, seven univariant curves, and five crystallization fields. Comparing the phase diagram of the system at 258.15 K to that at 298.15 K reveals that, except KCl, all crystallization zones have decreased, and LiCl·MgCl2·7H2O has the smallest crystallization zone compared to the other salts in the systems. This fundamental research could be valuable for promoting comprehensive utilization of the lithium-containing salt lake brine.