Bioleaching of low grade granitic chalcopyrite ore by hyperthermophiles: Elucidation of kinetics-mechanism

The current work was off-shoot of an attempt to isolate a thermophilic pyritic sulfur degrading bacteria in selective medium from a coal mine dump. This thermophilic bacteria (archaea) classified as Sulfolobus was tested for its feasibility to bioleach copper from a low grade Indian chalcopyrite ore (0.3% copper). With its prevalent ability to preferentially attack pyrite (a major phase in the ore), bioleaching was investigated at various parameters of pH, pulp density (PD), particle size, and temperature. A reflective high 85% copper recovery was obtained using <50 μm particles at 20% (w/w) pulp density, pH 2.0, 75 °C in 30 days. The copper dissolution was facilitated by iron (III) available in the leach liquor because of bacterial oxidation of pyrite present in the ore under acidic conditions. The biogenically generated Fe  (III) ions enhanced copper dissolution from the chalcopyrite ore. The bioleaching of copper appeared to follow chemical control kinetic model with the reaction of lixiviant-Fe  (III) and acid on the surface of the solid. Phase identification by XRD and SEM study corroborated the above mechanism of copper leaching.