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

• The metastable solubilities of the ternary system at 308.15 K were measured.
• The physicochemical properties of the ternary system at 308.15 K were reported.
• Reliable Pitzer single-salt parameter of lithium chloride at 308.15 K was obtained.
• The calculated and experimental solubilities agree well on basis of HMW model.

The solubilities and the physicochemical properties including density, viscosity, refractive index, conductivity, and pH of the aqueous ternary system (LiCl + Li2SO4 + H2O) at T = 308.15 K and p = 0.1 MPa 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 308.15 K were plotted. In the metastable phase diagram of the ternary system at 308.15 K, 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 308.15 K was fitted, and the single-salt parameters of lithium sulfate, mixing ion-pair θCl,SO4θCl,SO4, and the Debye–Hückel limiting slope AΦ at 308.15 K 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 308.15 K were calculated. A comparison shows that the calculated solubility agrees well with the experimental data.