Experimental determination and modeling of the solubility phase diagram of the ternary system (Li2SO4 + K2SO4 + H2O) at 288.15 K

•Solubility of the ternary system Li2SO4 + K2SO4 + H2O at 288.15 K has been measured.•Phase diagram of this system was simulated and calculated by a thermodynamic model.•Li2SO4·K2SO4 belongs to the incongruent double salt in this system.•Solution density was calculated using empirical equation.

The solubility and density in the thermodynamic phase equilibria ternary system (Li2SO4 + K2SO4 + H2O) at 288.15 K and 0.1 MPa were investigated experimentally with the method of isothermal dissolution equilibrium. This system at 288.15 K consists of two invariant points, three univariant isothermal dissolution curves; and three crystallization regions. The salt Li2SO4·K2SO4 belongs to the incongruent double salt, and no solid solution was found. Based on the Pitzer model and its extended Harvie–Weare (HW) model, the mixing ion-interaction parameters of θLi,K, ψLi,K,SO4 at 288.15 K and the solubility equilibrium constants Ksp of solid phases Li2SO4·H2O and Li2SO4·K2SO4, which are not reported in the literature were acquired. A comparison between the calculated and experimental results at 288.15 K for the ternary system shows that the calculated solubilities obtained with the extended HW model agree well with experimental data.

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