Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

To understand the thermodynamic characteristics of the brine located in Qaidam Basin salt lake, including the stable equilibrium solubilities, densities, and refractive indices in the quaternary system Li2SO4 + Cs2SO4 + MgSO4 + H2O were studied at T = 298.2 K using isothermal dissolution method. Chemical analysis and XRD were applied to determine the crystalloid forms of the solid phases. In this aqueous equilibrium system at 298.2 K, two double salts (3Li2SO4*Cs2SO4*2H2O and Li2SO4*Cs2SO4) generated from lithium sulfate and cesium sulfate; and one double salt produced between cesium and magnesium sulfate with the form of Cs2SO4*MgSO4*6H2O; no complex salts (such as double salt or solid solution) are observed between lithium sulfate and magnesium sulfate. The stable phase diagram consists nine univariant curves, six crystallization areas, four invariant points (include two commensurate points E1 & E4, and two incommensurate points E2 & E3). The six crystallizations are corresponding to three single salts (Li2SO4*H2O, Cs2SO4, and MgSO4*7H2O) and three types of double salts (3Li2SO4*Cs2SO4*2H2O, Li2SO4*Cs2SO4, and Cs2SO4*MgSO4*6H2O). Amongst, salt Cs2SO4 has the smallest crystallization region and is difficult to be directly separated from the brine in Qaidam Basin.