Solid–liquid metastable equilibria in the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K

Solubility in the liquid–solid metastable system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K was studied using the isothermal evaporation method. Based on experimental data, dry-salt phase and water-phase diagrams of the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturation point, three metastable solubility isotherm curves, and three crystallization regions corresponding to lithium sulphate monohydrate (Li2SO4·H2O), epsomite (MgSO4·7H2O), and mirabilite (Na2SO4·10H2O). Neither a solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β(0), β(1), β(2), and CΦ for Li2SO4, MgSO4, and Na2SO4, the mixed ion-interaction parameters θLi,Na, θLi,Mg, θNa,Mg, Ψ Li,Na,S O 4 , Ψ Li,Mg,S O 4 , and Ψ Na,Mg,S O 4 , and the Debye–Hückel parameter AΦ in the quaternary system at 263.15 K were obtained. The solubility of the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K was also calculated. A comparison between the calculated and experimental results shows that the predicted solubility agrees well with experimental data.