Complete gold extraction and recovery from double refractory gold ores by thiourea after bio-oxidation

摘要: Cyanidation, a conventional process to extract gold from gold ores, has been used for over 130 years in industrial mining because of the high efficiency and rate of formation of Au(CN)2− and the high recovery efficiency by adsorption of Au(CN)2− on activated carbon. However, carbonaceous refractory gold ores are not targeted because Au(CN)2− is easily adsorbed on carbonaceous matter in the ores, resulting in high recovery loss. In this study, the flotation concentrates of a carbonaceous refractory gold ores was subjected to biooxidation at 45 °C using a mixed culture containing iron-oxidizing and sulfur-oxidizing bacteria, followed by gold extraction using thiourea under strongly acidic conditions. The gold extraction efficiency reached ∼100% in 12 h without re-adsorption. Finally, the quantitative recovery of the Au(CS(NH2)2)2+ complex was confirmed by adsorption on strongly cationic exchange resin …