The effects of dissolved oxygen and cyanide dosage on gold extraction from a pyrrhotite-rich ore

The results of cyanidation of a pre-oxidized pyrrhotite-rich gold ore in laboratory leaching experiments and in plant trials are presented to highlight the effects of particle size, oxygen and cyanide concentrations during pre-oxidation and cyanidation on the overall gold extraction. The Multi Mix Systems (MMS) unit for oxygen injection significantly enhances the mass transfer of reagents and allows the achievement of high gold extraction. Pre-oxidation of ore of P80=63 μm for 12 h followed by cyanidation at a molar ratio of [CN−]/[O2]≈12 provided the best gold extraction in the first cyanidation tank. The %Au extracted in the first cyanidation tank reached a maximum of 83% when the product [CN−]×[O2] reached ≈5.6 mmol2 L−2.