The novel application of ferricyanide as an oxidant in the cyanidation of gold and silver

Low gold and silver extractions have often been observed in the traditional gold–silver cyanidation process. The reactivity and availability of oxidant is a potential limitation for gold and silver dissolution in cyanide solution, especially in heap leaching operations. The oxidant reactivity seems to have more of an effect on silver extraction due to the different mineralogy of gold and silver in the ores. For example, the occurrence of silver sulfides such as acanthite (Ag2S) typically results in low overall silver extraction which may be due to slow kinetics of oxygen reduction on the acanthite mineral. The leaching of metallic gold and silver sulfide in the novel ferricyanide–cyanide leaching medium was investigated. The potential application of ferricyanide as a supplemental oxidant in gold–silver cyanidation process was proposed and the possible reagent regeneration methods were discussed.