OPTIONS OF GOLD AND COPPER RECOVERY FROM GLYCINE AND GLYCINE-CYANIDE SOLUTIONS

摘要

The glycine based technology for gold and copper leaching was invented and patented at Curtin University in 2013. Leaching gold in starved or low cyanide solutions in the presence of glycine and an oxidant significantly improved the gold recovery and reduced the cyanide consumption (GlyCat? Process). The glycine-only system (GlyLeach~(TM)) can also effectively leach copper and other base metals such as nickel, cobalt, zinc and lead.The downstream processing of solutions from the leaching of copper and copper bearing gold ores in different glycine leach systems is critical for the successful implementation of the new leach system at an industrial scale.This paper outlines the successful options for copper and gold recovery from both glycine and glycine-cyanide solutions. The use of solvent extraction, sulfide precipitation, and ion exchange resins for copper recovery were tested, while activated carbon and ion exchange resins were used to evaluate the gold recovery from glycine solutions. More than 99% of copper was recovered as covellite by sulphide precipitation. Solvent extraction results showed that copper glycinate at alkaline pH (pH 10.0) can be easily loaded onto LIX84 extractant followed by sulphuric acid stripping. Chelating ion exchange resins efficiently and selectively adsorbed the cupric copper over gold complexes from alkaline glycine solutions. After the copper recovery by sulphide precipitation, ion exchange or solvent extraction, it was shown that the complexed glycine with the cupric ions was released back to the leach solutions and does not adsorb onto the extractants or precipitates. It was also seen that the activated carbon had a high adsorption tendency towards gold over copper from glycine-cyanide solutions. The gold and copper adsorption on carbon from a cyanide-glycine solution containing 2 mg/L gold, 300 mg/L copper, pH 11, 5 g/L glycine, Cu:CN of 1:1 (123 mg/L CN) and 8 g/L carbon in 24 hours reached 99.0% and 52.8% respectively. Activated carbon was found to be very selective for gold glycinate over cupric glycinate from glycine only solutions. More than 99.0% gold was adsorbed in 24 hours and less than 15% copper was adsorbed at the same time under optimum conditions from a glycine solution containing 7.5 g/L glycine, 2 ppm gold and 40 ppm copper.The optimum process for copper and gold recovery from glycine-cyanide solutions was found to be an initial copper recovery by either sulphide precipitation or ion exchange resin followed by gold recovery with activated carbon.