Phase equilibria of ternary systems: LiCl–MClx (M = Na+, Mg2+, Sr2+)–H2O systems at 1 bar and volume properties from 1 to 1000 bar (T = 298.2 K)

There are abundant lithium resources in seawater and brines. The thermodynamic phase equilibria of salt-water systems containing lithium have significant advantages to separation lithium from brines. Consequently, measurement and prediction of phase equilibria of LiCl–MCl_x (M = Na⁺, Mg²⁺, Sr²⁺)–H₂O ternary systems are investigated at 298.2 K and 1 bar. The phase equilibria are determined using the isothermal dissolution equilibrium method and the solubilities of salts in the ternary systems are predicted using the Pitzer model. The predicted solubilities agree well with experimental data at 298.2 K and 1 bar.

Then, the changes of volume property ($\Delta {\overline{V}}_{\text{dis}}^0$) and compressibility ($\Delta {\overline{\kappa }}_{\text{dis}}^0$) of three ternary mixed solutions at high pressure of 1–1000 bar were obtained in this work. The solubility product constants K_sp of salts at high pressure are calculated in detail. The thermodynamic prediction model of the phase equilibria is developed at high pressure of 1–1000 bar accordingly. The predicted phase equilibria at high pressure of 1–1000 bar are discussed and compared detailly.