Enhanced ferric sulphate leaching of copper from CuFeS2 and C particulate aggregates

Significantly faster leaching kinetics for ferric sulphate are achieved for particulate aggregates of CuFeS2 and C than for CuFeS2 itself. The effect of carbon particles upon the rate of dissolution of chalcopyrite has been increased by a factor of 4 (after 10 hours' leaching), depending upon the carbon type, which varies in electronic conductivity and particle size. Interestingly, when the carbon content is reduced, even to 2 per cent, the enhanced leaching by ferric sulphate is sustained. The leaching characteristics of aggregates of CuFeS2 and C are described from reaction-rate experiments, conductivity measurements, and scanning-electron-microscope photographs of the elemental-sulphur reaction product. The results provide further evidence for the kinetic significance of the elemental-sulphur reaction-product layer in the leaching of chalcopyrite by ferric sulphate. Rate control by surface reaction is extended in the presence of carbon particles, but eventually the rate appears to become limited by the transport of electrons through the elemental-sulphur reaction-product layer, as was suggested in previous studies.