Oxidation Rate of Pyrite from Brazilian Coal as Affected by CaCO3, Oxygenation, and Crystal Size

Abstract

This study evaluated the effects of crystal size, CaCO3 and H2O2 simulated oxygenation doses on the kinetics of pyrite (FeS2) oxidation in order to better predict the potential behavior of pyrite in various mine backfill settings in Brazil. As expected, oxidation rate decreased with increasing crystal size and was slower at higher doses of CaCO3, except for the finest grains, where a liming effect was not evident. These results suggest microencapsulation via precipitation of Fe onto surfaces of the pyrite crystals leading to decreasing oxidation rates. Higher doses of CaCO3 were necessary to stabilize pyrite at the lowest oxygenation levels, but the reaction efficiency of CaCO3 was decreased at higher concentrations of H2O2. These data point out the importance of understanding the fundamental interactions of pyrite grain size, oxygenation, and the potential for Fe-oxide armoring when liming pyritic materials.