Determination of the solubility of MgSO4in the Zinc hydrometallurgy system within the temperature range of 263.15 K–293.15 K

ABSTRACTSolid–liquid equilibrium solubility of magnesium sulphate (MgSO4) is essential for designing and optimising the removal and recovery of magnesium (Mg) from standard zinc (Zn) hydrometallurgy systems via freeze crystallization. In this study, the solubility data of MgSO4in ternary system MgSO4-H2SO4-H2O and quaternary system MgSO4-ZnSO4-H2SO4-H2O were determined in different zinc sulphate (ZnSO4) concentrations and sulphuric acid (H2SO4) concentrations through the isothermal equilibrium method within the temperature range from 263.15–293.15 K. The results indicated that the solubility of MgSO4decreased with decreasing temperature and increasing concentrations of H2SO4and ZnSO4. Furthermore, the modified Apelblat equation was applied to correlate the experimental solubility data, yielding results consistent with the experimental findings. Furthermore, X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy SEM-EDS analysis results indicated that the main phases of the equilibrium solid consist of mixed crystallization products of Zn sulphate heptahydrate (MgSO4·7H2O) and Mg sulphate heptahydrate (ZnSO4·7H2O). The microstructure of the equilibrium solid was affected by the sulphate concentration.