Gold recovery from a refractory arsenopyrite (FeAsS) concentrate by in-situ slurry oxidation

Arsenopyritic gold is a major source of refractory gold not amenable to roasting. Bio-oxidation is a popular treatment option but is slow and needs careful control of the As content of the feed. Electrochemical slurry oxidation in-situ with chlorine in acidified salt water in a membrane cell reactor has been evaluated at laboratory-scale level as a potential processing route. A refractory mine concentrate (cyanideable gold content ∼ 7%) containing arsenopyrite (FeAsS), pyrite (FeS2) and gersdorffite (NiAsS) has been used to demonstrate that gold recovery > 90% could be achieved. Reaction rates are but sale of the co-produced NaOH can be a valuable process credit. This route can provide a more environmentally friendly process flow-sheet than carbon-in-pulp/leach processing and can be applied to a small or large resource.