Thermodynamic model for acidic Ni(II) sulfate from solubility data

Acidic nickel sulfate solutions are generated in a large scale in the hydro- and pyrometallurgical industries. They are also produced in many industrial processes from nickel refining to surface finishing of metals by electroplating. Acid mine drainage has long been a significant environmental problem in coal and metal mining. The demand of recycling and reuse of materials has increased significantly especially in EU. Dumping a neutralized deposit is not an option any more. Thus, several techniques of recycling and reuse of sulfuric acid and/or metal sulfates from the side streams are needed. eveloping alternative solutions, a better understanding of the thermodynamic behavior of NiSO4–H2SO4–H2O system is needed. In this study a thermodynamic model of this system has been developed in order to yield a thermodynamically consistent set of values for the solubility of nickel sulfate in a wide temperature and concentration range. The current model presents the experimental data available with a good accuracy and consistently up to 90 °C, and sulfuric acid concentrations up to 10 mol/kg. The model also predicts well the solubility measurements available in dilute up to 1.55 mol/kg sulfuric acid solutions at 200–250 °C.