Integrated recovery of metals from complex substrates

A method for recovering at least one metal from a substrate comprising a metal sulphide, or a combination of the metal sulphide and a metal oxide, the method comprising:

• a) leaching the substrate with an aqueous oxidant in an amount sufficient to oxidize the metal sulphide to elemental sulphur and oxidized metal and to convert the metal oxide, if present, to a metal salt, to obtain a pregnant solution and a solid, wherein the solid comprises the oxidized metal and metal salt, if present,
• wherein an oxidation potential of the aqueous oxidant is actively-adjusted to, and maintained at, a desired oxidation potential that is insufficient to oxidize the metal sulphide to a hexavalent state,
• wherein said leaching is conducted under ambient temperature conditions and ambient pressure conditions;
• b) separating the solid and the pregnant solution obtained in step a), wherein the solid comprises the oxidized metal and metal salt, if present;
• c) leaching the solid obtained in step b) comprising the oxidized metal and metal salt, if present, with ammonium hydroxide to form a soluble metal ammine complex to obtain a leachate and residual solids;
• d) separating the leachate from the residual solids;
• and
• e) recovering the at least one metal from one or more of the leachate and the residual solids, wherein:
• the substrate comprises silver,
• the soluble metal ammine complex comprises a soluble silver ammine complex, and
• recovering the at least one metal comprises recovering silver from the leachate.