Solid-liquid stable phase equilibria of the ternary systems MgCl 2 + MgB6O10+ H2O and MgSO 4 + MgB6O10 + H2O at 308.15 K

Abstract

The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β(0), β(1), β(2) and C Ø for MgCl2, MgSO4, and Mg(B 6O7)(OH)6, the mixed ion-interaction parameters θCl,B6O10, θSO4,B 6O10, Ψ Mg,Cl,B6O10, Ψ Mg,SO4,B6O10 of the systems at 308.15 K were fitted, In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.