Experimental and Predictive Equilibrium Thermodynamics of the Aqueous Ternary System (LiCl + CaCl2 + H2O) at T = 288.15 K

As an energy metal, lithium is widely used in many fields. With the depletion of the solid mineral resource, to extract and recover lithium from liquid brines is going toward an inevitable trend in the future. In order to utilize the worthy lithium-containing brine resources in the world efficiently, the experimental equilibrium solubility and the solution physicochemical properties including density (ρ), refractive index (nD), and pH for the aqueous ternary system (LiCl + CaCl2 + H2O) at T = 288.15 K were determined using the isothermal dissolution equilibrium method. In addition, the calculated values of refractive index and density obtained by using empirical equations agree well with the experimental data. According to the Pitzer extended Harvie and Weare model (HW model) of electrolyte ion-interaction theory, the single-salt parameters β(0), β(1), and Cϕ of LiCl and CaCl2, the mixing ion-interaction parameters θLi,Ca and ΨLi,Ca,Cl, and the equilibrium constants of solid phases LiCl·2H2O, CaCl2·6H2O, and LiCl·CaCl2·5H2O existed in the system at 288.15 K were obtained for the first time. The theoretical predictive equilibrium solubilities for this ternary system at 288.15 K agree well with the experimental value, and this result indicates that the Pitzer single-salt parameters, the mixing ion-interaction parameters, and the equilibrium constants obtained in this work are reliable. The results for the system containing lithium in this study are essential for the development of universal thermodynamic models for brine systems containing lithium.