Thermodynamic Phase Equilibria of the Aqueous Ternary System (LiCl + LiBO2 + H2O) at 308 K: Experimental Data and Predictions Using the Pitzer Model

Solubilities and physicochemical properties including density, pH value, refractive index and conductivity of a ternary system (LiCl + LiBO2 + H2O) at 308 K were determined with the isothermal dissolution equilibrium method. Two hydrates of lithium metaborate, i.e., lithium metaborate octahydrate (LiBO2 center dot 8H(2)O, Lb1) and lithium metaborate dihydrate (LiBO2 center dot 2H(2)O, Lb2), in the ternary system are found for the first time. On the basis of the experimental data, the phase diagram and the physiochemical properties versus composition diagram in the ternary system at 308 K were plotted. There are two invariant points of (Lb1 + Lb2) and (Lb2 + Lc), three univariant curves, and three crystallizing zones correspond to Lb1, Lb2 and lithium chloride monohydrate (LiCl center dot H2O, Lc). Physicochemical properties (density, pH, refractive index and conductivity) in the ternary system change regularly with the increasing of lithium chloride mass fraction in the solution. Based on the Pitzer ion-interaction model and its extended HW model, the Pitzer single-salt parameters of LiBO2 and LiCl, and the mixing ion-interaction parameters (theta(B(OH)4, Cl,) psi(Li, B(OH)4, Cl)) were parameterized, which are not reported in the literature. The calculated values of the ternary system at 308 K agree well with the experimental results.