Thermodynamic Analysis Of Gold Leaching By Ammoniacal Thiosulfate Using Eh/Ph And Speciation Diagrams (1b00c1b6-1d3c-49da-aa8d-881dd0b4bd68)

Thiosulfate offers a non-toxic 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 optimise 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.