Solid-liquid phase equilibria in the ternary system (LiBO₂ + Li₂CO₃ + H₂O) at 288.15 and 298.15 K

Abstract

Experimental studies on the solubilities and physicochemical properties including density, refractive index and pH value in the ternary systems (LiBO₂ + Li₂CO₃ + H₂O) at 288.15 and 298.15 K were determined with the method of isothermal dissolution equilibrium. Based on the experimental results, the phase diagrams and their corresponding physicochemical properties versus composition diagram in the system were plotted. In the phase diagrams of the ternary system at 288.15 and 298.15 K, there are one eutectic point and two crystallization regions corresponding to lithium metaborate octahydrate (LiBO₂ · 8H₂O) and lithium carbonate (Li₂CO₃), respectively. This system at both temperatures belongs to hydrate type I, and neither double salt nor solid solution was found. A comparison of the phase diagrams for this ternary system at 288.15 and 298.15 K shows that the solid phase numbers and exist minerals are the same, and the area of crystallization region of Li₂CO₃ is increased obviously with the increasing temperature while that of LiBO₂ · 8H₂O is decreased. The physicochemical properties (density, pH value and refractive index) of the solutions of the ternary system at two temperatures changes regularly with the increasing lithium carbonate concentration. The calculated values of density and refractive index using empirical equations of the ternary system are in good agreement with the experimental values.