Solid and liquid metastable phase equilibria in the aqueous quaternary system Li + , Mg 2+ //SO 4 2– , borate-H 2 O at 273.15 K

The metastable phase equilibria of the Li+, Mg2+//SO4 2–, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical property diagrams of the system were plotted with the metastable solubility values and physicochemical properties corresponding to density, refractive index, pH value and conductivity. The dry-salt diagram was composed of four crystallizing zones[lithium sulfate hydrate(Li2SO4·H2O), epsomite(MgSO4·7H2O), lithium metaborate octahydrate(LiBO2·8H2O), and hungchaoite(MgB4O7·9H2O)], five univariant curves and two invariant points (Li2SO4·H2O+MgSO4·7H2O+MgB4O7·9H2O and Li2SO4·H2O+LiBO2·8H2O+MgB4O7·9H2O). Li2B4O7 converted into LiBO2 in solution. Comparing the metastable phase diagram at 273.15 K and stable phase diagram at 298.15 K for the system, the crystallized area of Li2SO4·H2O and MgSO4·7H2O became large, whereas, the other phase regions became small. The J(H2O) changes regularly with increasing J(SO4 2‒), and the physicochemical properties change regularly with the concentration of B4O7 2‒ increasing.