Phase Equilibria in the Aqueous Ternary System (LiBO2 + CaB2O4 + H2O) at 288.15 and 298.15 K

Abstract

The solubilities and physicochemical properties, including density and pH, in the ternary system (LiBO2 + CaB2O4 + H2O) at (288.15 and 298.15) K were investigated using the isothermal dissolution equilibrium method. According to the experimental results of the ternary system at (288.15 and 298.15) K, the stable phase diagrams and the diagrams of physicochemical properties were plotted versus composition. In the phase diagrams of the ternary system at (288.15 and 298.15) K, there is one invariant point (LiBO2·8H2O + CaB2O4·6H2O), two univariant isotherm dissolution curves, and two crystallization regions corresponding to lithium metaborate octahydrate (LiBO2·8H2O) and calcium metaborate hexahydrate (CaB2O4·6H2O), respectively. This system at both temperatures belongs to hydrate type I classification and neither double salt nor solid solution were found. A comparison of the phase diagrams for the ternary system at (288.15 and 298.15) K shows that the numbers of solid phase and the minerals present are the same; the crystallized area of CaB2O4·6H2O increased at the higher temperature, while that of LiBO2·8H2O decreased. The physicochemical properties (density and pH values) of the ternary system at the two temperatures change regularly with increasing lithium metaborate concentration. The calculated values of density using empirical equations of the ternary system are in good agreement with the experimental values.