Hydrochloric acid pressure-oxidation of a pyrite concentrate from the Vaal Reefs East Gold Mine

The extraction of refractory gold from pyrite concentrate by hydrochloric acid pressure oxidation was investigated on laboratory scale. The aim was for direct solubilization of refractory gold by chloride pressure-leaching without cyanidation. The experiments were carried out at temperatures in the range of 170°C to 200°C, with various concentrations of sodium chloride and hydrochloric acid under an oxygen partial pressure of 1500 kPa, with retention times varying from two to six hours. The results showed that it was possible to obtain a gold recovery of 94.9% under the optimum conditions.