Solid–Liquid Phase Equilibrium of MnSO₄–MgSO₄–H₂O and (NH₄)₂SO₄–MnSO₄–MgSO₄–H₂O Systems at T = 303.15 K

Abstract

In this study, the stable (solid + liquid) phase equilibrium and physical–chemical properties of the ternary MnSO4–MgSO4–H2O system at T = 303.15 K have been determined by the method of isothermal solution saturation. It is found that there are three crystalline regions, one unsaturated crystallization region, and one invariant point. The density and refractive index of this system were compared with the experimental values, and it is found that there is little difference between the two systems. The experimental solubility data were compared with the literature values, and the invariant points at different temperatures were fitted to provide data for the water-salt system containing manganese sulfate and magnesium sulfate. At the same time, the solubility data of the MnSO4–MgSO4–(NH4)2SO4–H2O system were determined by the same method, and the phase diagram was drawn. Comparing the actual phase diagram measured by the experiment with the predicted phase diagram obtained by means of translation method, it is found that they have the same crystallization regions. In order to see more clearly the relationship between the quaternary MnSO4–MgSO4–(NH4)2SO4–H2O system and its three ternary sub-systems (MnSO4–(NH4)2SO4–H2O, MgSO4–(NH4)2SO4–H2O, and MnSO4–MgSO4–H2O), we have plotted the related stereoscopic phase diagram. The research of this study provides the data basis for the crystallization process of manganese sulfate.