Abstract
In the hydrometallurgical processes for treatment of zinc leach residues, the residues were dissolved in high sulfuric acid solutions at about 100°C.In the hematite process, the dissolution of zinc leach residues is carried out under the reducing conditions.Accordingly, the hematite process starts from oxidation of ferrous sulfate solution.In order to explain the mechanism of the hematite process, it is necessary to know the solubility of ferrous sulfate in aqueous solutions at high temperatures.The solubility of ferrous sulfate in pure water and sulfuric acid solutions has been clarified up to 100°C.Above 100°C, only the solubility of ferrous sulfate in pure water from 120 to 180°C was reported.
We have determined experimentally the solubility of ferrous sulfate in pure water and sulfuric acid solutions from 130 to 220°C and the effect of coexisting zinc or magnesium sulfate on the solubility of ferrous sulfate in aqueous solutions has been made clear at 200°C. The experimental result shows that the solubility of ferrous sulfate steeply decreases with an increase in temperature and increases with an increase in sulfuric acid concentration.The solubility of ferrous sulfate in pure water and sulfuric acid solutions decreases with an addition of zinc or magnesium sulfate at 200°C.
