Solid–Liquid Phase Equilibria of the Quaternary system Li2SO4–LiBO2–Li2B4O7–H2O and the Ternary Subsystem LiBO2–Li2B4O7–H2O at T = 288.15 K and p = 0.1 MPa

Abstract

The solubilities, densities, refractive indices, and pH values in the systems LiBO2–Li2B4O7–H2O and Li2SO4–LiBO2–Li2B4O7–H2O at 288.15 K were studied by the classical dissolution method in this paper. The solid–liquid equilibrium phase diagrams and the physicochemical property diagrams were constructed with the experimental results. The phase diagram of the ternary system is composed of two single-salt crystallizations of LiBO2·8H2O and Li2B4O7·3H2O, two solubility univariant curves, and one invariant point saturated with the above salts. The comparison for the phase diagrams in the ternary system at different temperatures shows that the solubilities of lithium metaborate and lithium tetraborate in this system are in a positive correlation with the temperature. The dry-salt diagram of the quaternary system consists of three single-salt crystallization fields for Li2SO4·H2O, LiBO2·8H2O, and Li2B4O7·3H2O, three univariant solubility curves, and one invariant point. The physicochemical properties in the two systems change regularly as the concentration increases in solution. The calculated densities and refractive indices with empirical equations are in good agreement with the experimental results.