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

抄録

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 (LiBO₂·8H₂O, Lb1) and lithium metaborate dihydrate (LiBO₂·2H₂O, 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·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 (θ_{B(OH)4, Cl}, ψ_{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.