Solid–liquid metastable equilibria in the quaternary system Li 2SO 4 + MgSO 4 + Na 2SO 4 + H 2O at T = 263.15 K

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Solubility in the liquid–solid metastable system Li 2SO 4 + MgSO 4 + Na 2SO 4 + H 2O 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 (Li 2SO 4·H 2O), epsomite (MgSO 4·7H 2O), and mirabilite (Na 2SO 4·10H 2O). 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 C Φ for Li 2SO 4, MgSO 4, and Na 2SO 4, the mixed ion-interaction parameters θ Li,Na, θ Li,Mg, θ Na,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 A Φ in the quaternary system at 263.15 K were obtained. The solubility of the quaternary system Li 2SO 4 + MgSO 4 + Na 2SO 4 + H 2O 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.