Reaction kinetics and oxidation mechanisms of the conversion of pyrite to ferrous sulphate: A Mossbauer spectroscopy study

摘要

Pyrite undergoes a series of exothermic reactions during mine roasting to porous hematite. At low temperatures, the first non-refractive phase to form is ferrous sulphate and could be a cheaper alternative to hematite roasting for the mining industry. In this study, pyrite powder is heated in air at temperatures between 200 and 370 degrees C for 1 to 256 h in a temperature and time series. The rate of oxidation of pyrite to ferrous sulphate is modelled by combining the Arrhenius equation with the Weibull function to extract reliable thermodynamic data, including the energy of activation, the frequency factor and the overall order of reaction. From the thermodynamic data obtained, two possible oxidation mechanisms are recognized, depending on the bond dissociation energies of the S-S and Fe-S bonds in pyrite.