Solubility of calcium sulfate salts in acidic manganese sulfate solutions from 30 to 105 °C

Abstract

Solubility determinations of gypsum were conducted on simulated process liquors containing 0–72 g/kg solution Mn 2+ (as sulfate) and 0–72 g/kg solution H 2SO 4 from 30 °C to 105 °C. At temperatures ≤ 80 °C gypsum solubility was shown to increase with increasing H 2SO 4 concentration and temperature in accord with the dissociation equilibrium of the bisulfate ion, while the addition of Mn 2+, as sulfate, decreased the solubility. Above 80 °C the conversion of gypsum to anhydrite was shown to be dependent on Mn 2+ and H 2SO 4 concentrations. In water alone hemihydrate was produced at 105 °C. Several empirical models were developed from solubility data at temperatures ≤ 80 °C and correctly predicted gypsum solubility in the experimental acidic manganese solutions.