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Thiosulphate Leachof a Twins Creek Ore Abstract Current environmental issues surrounding the use of cyanide in gold production, as well as other precious metals, have led to a search for a more attractive alternative. Several reagents have been considered, including: chlorine, bromine, iodine, thiocyanate, thiourea, ammoniacal thiosulphate (ATS), and ammoniacal copper cyanide. Thiosulphate (S2O3-), more specifically ammoniacal thiosulphate, has been chosen as one of the better ligands in gold leaching, and the focus of this study. It has shown to yield recoveries comparable to those for cyanidation in certain ores: sulphide (Kerley, 1981), sulphide carbonaceous (Marchbank et al., 1996) and gold copper (Yen et al., 1998). Other research shows that thiosulphate can leach in ammoniacal (NH3) (Muir et al., 2004) and non-ammoniacal (OH-) environments (Senanayake, 2005). Ammoniacal thiosulphate requires the addition of ammonia to act as a stabilizer and, the cupric ion, Cu2+, to act as an oxidizer and catalyst. Several ores have been leached with ATS and have reached gold recovery levels comparable to that of cyanidation but each ore requires parameters tailored specifically to that ore including but not limited to: pH, EH and initial concentrations of Cu++, S2O32- and NH3. Results of our study with a Twins Creek are reported along with reaction mechanisms. Acknowledgements Biography
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