Metastable Phase Equilibrium in the Reciprocal Quaternary System LiCl+MgCl₂+Li₂SO₄+MgSO₄+H₂O at 348.15 K and 0.1 MPa

Abstract

The metastable solubilities and the physicochemical properties including density and pH of the reciprocal quaternary system(LiCl+MgCl₂+Li₂SO₄+MgSO₄+H₂O) at 348.15 K and 0.1 MPa were determined using the isother-mal evaporation method. The dry-salt diagram and water-phase diagram were plotted based on the experimental data. There are five invariant points, eleven univariant curves, and seven crystallization zones corresponding to hexahy-drite, tetrahydrite, kieserite, bischofite, lithium sulfate monohydrate, lithium chloride monohydrate and lithium car-nallite. Comparison between the stable and metastable diagrams at 348.15 K indicates that the metastable phenome-non of magnesium sulfate is obvious, and the crystallization regions of hexahydrite and tetrahydrite disappear in the stable phase diagram. A comparison of the metastable dry-salt phase diagrams at 308.15, 323.15 and 348.15 K shows that with the increasing of temperature the epsomite crystallization zone disappears from the dry-salt phase diagram of 303.15 K, and a new kieserite crystallization zone is presented at 348.15 K. The density and pH in the metastable equilibrium solution present regular change with the increasing of Jänecke index J(2Li⁺), and the calculated densities using the empirical equation agree well with the experimental values.