Cyanidation Leaching of Gold: A Critical Review of Chemistry, Kinetics, Mineralogical Controls, Process Integration, Industrial Performance, and Future Directions

Cyanidation remains the reference hydrometallurgical route for gold extraction because the dicyanoaurate complex is highly stable under alkaline, oxidizing conditions and because the process integrates with mature adsorption, precipitation, and electrowinning circuits. This critical review examines the process as a coupled system rather than as an isolated leaching reaction. It evaluates interfacial chemistry, mixed-potential behavior, mass transfer, mineralogical accessibility, cyanicide reactions, preg-robbing, pretreatment, operating-variable interactions, gold recovery, cyanide recycling, detoxification, and industrial scale-up. Particular emphasis is placed on why nominally similar laboratory extractions frequently diverge at plant scale: feed variability, oxygen-transfer limitations, competing metal complexes, solution recycle, carbon performance, and water chemistry alter the effective operating window. The review also compares conventional cyanidation with intensified and hybrid routes, including glycine–cyanide systems and alternative lixiviants. A mineralogy-to-flowsheet framework is proposed that evaluates recovery, reagent demand, water closure, residue quality, and process risk simultaneously. The synthesis shows that the principal opportunity is not a universal replacement of cyanide but a more selective use of cyanide within integrated, mineralogy-informed, recycle-oriented flowsheets that minimize total environmental and economic burdens while preserving high gold recovery