Leaching of a zinc concentrate in H2SO4 solutions containing H2O2 and complexing agents

摘要

The extraction of zinc from a sphalerite concentrate by means of hydrogen peroxide as oxidant in sulfuric acid solutions was examined. The oxidative leaching study was focused on two topics: the kinetics of zinc dissolution, and the search of complex agents to increase the recovery of zinc in the oxidizing aqueous media. In a first stage, the study was carried out to assess the influence of various parameters as acid and peroxide concentrations, reaction time and temperature, on the kinetics of zinc dissolution. It was found that the oxidative leaching of sphalerite follows the shrinking-core model and, in spite of the layer of elemental sulfur (S~0 surrounding the particles, the dissolution is controlled by the step of reaction control with an activation energy of 50 kJ/mol. The addition of phosphonic acid, phosphoric acid, oxalic acid, and citric acid enhances the leaching of the sphalerite. The use of complexing agents constitutes an option to improve the zinc dissolution.