Electro-oxidation as a pre-treatment for gold recovery

Electro-oxidation as a potential alternative process to conventional pre-treatment of a refractory gold ore was investigated. A particulate bed anode of a Portuguese concentrate containing gold was electroleached in a two-compartment electrolytic cell and the anodic residue leached with thiourea. The effectiveness of the electrochemical treatment is emphasized by comparison with the results of direct leaching under similar conditions. Up to 90% gold extraction was obtained after electrolytic pre-treatment while only 21% was extracted by direct thiourea leaching. A comparison between chemical and electrochemical oxidation using chloride and sulphate solutions was also carried out. The results demonstrate the better performance of chloride media and that the electrolytic route enhances the amount of precious metal dissolved. The influence of the operative parameters (e.g., temperature, electrolysis time, current and slurry density) on the overall gold extraction are discussed.