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

The extraction of zinc from a sphalerite concentrate by means of hydrogen peroxide as an oxidant in sulfuric acid solutions was examined. The oxidative leaching study focused on two topics: zinc dissolution kinetics, and finding complex agents that increase zinc recovery in an oxidative aqueous medium. In the first stage, a study was performed to assess the influence of various parameters such as acid and peroxide concentrations, particle size, reaction time, and temperature on zinc dissolution kinetics. It was found that oxidative leaching of sphalerite follows the shrinking core model and, in spite of the layer of elemental sulfur surrounding the particles, the dissolution is controlled by a reaction control step with an activation energy of 50 kJ/mol. The addition of phosphonic acid, phosphoric acid, oxalic acid, and citric acid enhanced the leaching of the sphalerite. The use of complexing agents is a viable option for zinc dissolution.