Phase equilibria in the ternary system (LiCl + Li2SO4 + H2O) at T = 308.15 K and p = 0.1 MPa: Experimental data and predictions using the Pitzer model

Abstract

The solubilities and the physicochemical properties including density, viscosity, refractive index, conductivity, and pH of the aqueous ternary system (LiCl+Li2SO4+H2O) at T=308.15K and p=0.1MPa were determined using the isothermal evaporation method, and the metastable phase diagram and the physicochemical property diagram versus composition of liquid phase solution for the system at 308.15K were plotted. In the metastable phase diagram of the ternary system at 308.15K, there is one invariant point, two univariant curves, and three crystallization zones corresponding to lithium sulfate monohydrate (Li2SO4·H2O), lithium chloride monohydrate (LiCl·H2O) and (Li2SO4·H2O+LiCl·H2O). It belongs to the hydrate type I, and neither double salts nor solid solution were found. On the basis of Pitzer ion-interaction theory of the electrolytes and the chemical equilibrium HMW model, Pitzer single-salt parameter of lithium chloride at 308.15K was fitted, and the single-salt parameters of lithium sulfate, mixing ion-pair θCl,SO4, and the Debye–Hückel limiting slope AΦ at 308.15K were obtained according to the temperature-dependent equation of parameters presented in the literatures. And then, the solubilities on the ternary system (LiCl+Li2SO4+H2O) at 308.15K were calculated. A comparison shows that the calculated solubility agrees well with the experimental data.