Experimental and Thermodynamic Modeling Study of the Solid–Liquid Equilibria in the Quaternary System (LiCl + MgCl2 + Li2SO4 + MgSO4 + H2O) at 288.15 K and 0.1 MPa

Solid–liquid phase equilibria of the quaternary system (LiCl + MgCl2 + Li2SO4 + MgSO4 + H2O) at T = 288.15 K and p = 0.1 MPa were investigated using the isothermal dissolution equilibrium method, and a dry salt diagram and a water diagram were plotted accurately. The phase diagram of this quaternary system includes four invariant points, nine univariant solubility curves, and six crystallization regions corresponding to Li2SO4·H2O, LiCl·2H2O, LiCl·MgCl2·7H2O, MgCl2·6H2O, MgSO4·7H2O, and MgSO4·6H2O. The double salt of LiCl·MgCl2·7H2O was found, and no solid solution was formed. The Pitzer model and its extended Harvie-Møller-Weare (HMW) model were used for predicting the solubilities of the quaternary system (LiCl + MgCl2 + Li2SO4 + MgSO4 + H2O) at 288.15 K, and the predicted results agree well with the experimental values.