The role of oxygen in cyanide leaching of gold ore

CIM Bulletin, Vol. 85, No. 963, 1992

K.E. Haque, CANMET-EMR, Mineral Sciences Laboratories, Ottawa, Ontario

This paper is a brief overview of the role of oxygen in cyanide leaching of gold feeds (e.g. ore, concentrate). As the majority of gold occurs in the elemental state (Au°), its oxidation is of vital importance for dissolution in the cyanide lixiviant. The cyanida-tion at high pH is favourable for the oxidation of Au° with a mild oxidant such as air or oxygen. Beside oxidation of gold, deleterious effects of soluble sulphides, arsenates, antimonates on cyanidation of gold can be alleviated by preaerating the leach slurry with air or oxygen (i.e. preaeration process). If gold is refractory due to its occlusion in sulphides, silicates, tellurides, etc. then gold liberation is possible by roasting in the presence of oxygen or by leaching under oxygen pressure. The data in the recent literature indicate that reactive oxygen supplied by Hf)2, Na2O2, CaO2 or O3 during cyanidation can accelerate considerably gold oxidation-cyanidation and yield high gold recovery in much shorter leach time. The information compiled in this review leads to the conclusion that oxygen plays a vital role in the dissolution of gold in cyanide lixiviant.

Keywords: Gold, Cyanide leaching, Chemistry of cyanidation, Oxidation, Preaeration, Active oxygen.