Thermodynamic modelling of aqueous Mn(II) sulfate solutions

The H2O–MnSO4 system has been modelled using the Pitzer activity coefficient approach over a temperature interval of −11–175 °C and in concentrations from pure water to the solubility limit of manganese sulfate hydrates, the maximum MnSO4 molality being 4.26 mol/kg at the MnSO4·5H2O(s) to MnSO4·H2O(s) transition temperature of 23.9 °C. The thermodynamic properties of MnSO4 hydrates were refined. The model in this work presents all the experimental data available, including the solubilities, mean activity coefficients, activities of water, enthalpy and heat capacity of solution and hydrate dissociation pressure, with good accuracy and consistently up to 175 °C, but the model has limitations at higher than 100 °C due to lack of experimental data.