The main purpose of the present work is to improve the understanding of an industrial process that exploits the synergic action of cyanide ion and three-nitrobenzene-sulphonate for the selective removal of precious metals from various matrices. It has been observed that the cyanide dissolves first gold from the surface, forming dicyanoaurate gold complexes, but this reaction alone is not sufficient to dissolve gold with the observed velocity. A deeper knowledge of the chemical mechanisms can potentially improve the process competitiveness. Important reaction factors have been identified and analyzed. It has been demonstrated that the cyanide amount presently utilized is excessive. Possible reduction products have been also identified. The results can help the search for cyanide reduction and substitution. Yield and velocity optimization, together with a solution toxicity reduction can pave the way to eco-friendly processes for the leaching of noble metals.
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