Solid-Liquid Phase Equilibria of the Quaternary System (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K: Experimental and Theoretical Prediction

Abstract

The isothermal dissolution equilibrium method was employed to obtain the solubilities and physicochemical properties of the quaternary system (LiCl + LiBO2 + Li2B4O7 + H2O) at 308.15 K in this work. The dry-salt phase diagram, water-phase diagram, and physicochemical properties, including density, refractive index, and pH against composition in the quaternary system, were established for the first time. The dry-salt phase diagram includes two invariant points, five univariate solubility curves, and four single salt crystalline phase regions (LiCl·H2O, LiBO2·2H2O, LiBO2·8H2O and Li2B4O7·3H2O), respectively. In addition, the physicochemical properties of density, refractive index, and pH in the system change regularly with the changing of the lithium metaborate concentration. Based on the Pitzer model, the mixing ion parameters of θCl,B4O5(OH)4, θB(OH)4,B4O5(OH)4 and Ψ(Li,Cl,B4O5(OH)4, ΨLi,B (OH)4,B4O5(OH)4 and the predictive solubilities in the quaternary system were fitted. Although there is a slight deviation between the calculated and experimental values, the solubility of boron in the quaternary system agrees well, which provides data support for the study of the solubility of boron.