Gold recovery from waste-activated carbon— a comparison between mechano-chemical pretreatment and charcoal augmented oxidation

Waste-activated carbon generated by gold ore processing plants that employ carbon adsorption technologies may contain very high gold values and represent a potential source of extra revenue. In this research, two methods that augment combustion of waste-activated carbon are evaluated. These are mechano-chemical activation and charcoal-enhanced ashing. It was found that mechano-chemical activation caused structural transformation of the waste carbon, which resulted in a reduction in the temperature for complete oxidation from above 700oC to 450oC. Complete oxidation was also achieved at the same furnace temperature, for a combined sample of waste-activated carbon and 50% by weight of wood charcoal. In both cases, gold was extracted from the ash by conventional cyanidation, with recoveries greater than 98% from a head grade of 3.2 kg/t.