Thermodynamic analysis of gold leaching by ammoniacal thiosulfate using Eh/pH and speciation diagrams

Aylmore, M. G. ; Muir, D. M.
Organization: Society for Mining, Metallurgy & Exploration
Pages: 7
Publication Date: Jan 1, 2002
Thiosulfate offers a nontoxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH3 and S2O32; It is shown that an understanding of the copper speciation and sulfur speciation is required to optimize this system. This paper presents Eh-pH and speciation diagrams for varying concentrations of Cu(II), S2O32- and NH3 and discusses the conditions under which various copper and sulfur species are stable.
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