Mechanism and Kinetics of the Thermal Oxidation of Natural Sphalerite

Resumo

The oxidation of natural sphalerite on heating in an oxidative medium is studied by thermogravimetry coupled with scanning calorimetry, mass spectrometry of released gases, and X-ray powder diffraction analysis. The mechanism of sphalerite oxidation when the particle surface is equally accessible and sulfur dioxide is removed from the reaction zone is the formation of ZnO, ZnFe₂O₄, and SO₂. The process is found to be one-stage, as determined by a nonisothermal kinetic method. The activation energies are from 293 to 317 kJ/mol depending on the model used. Natural sphalerite is oxidized in the kinetic regime, and the rate-determining steps are the formation and growth of new-phase nuclei.