Ammoniacal thiosulphate leaching of gold ore

R.K. Rath, N. Hiroyoshi, M. Tsunekawa*, T. Hirajima

Laboratory of Mineral Processing and Resources Recycling, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628, Japan

Received 30 November 2002; accepted 10 November 2003


Ammoniacal thiosulphate leaching of gold finds a better substitute as it is non-toxic and environmentally safe as compared to the toxic cyanide system for gold extraction. In the present study, an attempt is made to assess the feasibility of ammoniacal thiosulphate leaching of gold ore samples from two different mines namely Akeshi and Hishikari of Japan. In this study, the effect of thiosulphate concentration, effect of ammonia, effect of cupric ions, and few other variables affecting the gold leaching have been studied. The ammoniacal thiosulphate leaching of gold is dependant on both ammonia and thiosulphate concentration. The leaching is improved significantly at a particular ratio of ammonia to thiosulphate concentration and that ratio varies from ore to ore. Copper ions act as an oxidant and the gold dissolution increases substantially in the presence of them. The gold leaching is minimum in the presence of an inert gas such as nitrogen and the leaching increases in presence of other gases like oxygen and air.

Keywords: Ammoniacal thiosulphate; Gold; Leaching, Eh and pH

* Corresponding author
   E-mail : tunekawa@eng.hokudai.ac.jp