Application of pressure oxidation pretreatment to a double-refractory gold concentrate

CIM Bulletin, Vol. 85, No. 956, 1992

Kafui Nyavor and Nosa O. Egiebor, University of Alberta, Edmonton, Alberta

The effectiveness of sulphuric acid, nitric acid, and hydrogen peroxide pressure oxidation on the cyanide extractability of gold from a double-refractory concentrate is presented. While over 90% of the sulphide content could be oxidized by either of the two acid pretreatments, only 65% was achieved by the peroxide oxidation. Carbon oxidation by both acid and peroxide pressure oxidation were less than 15%. Although the peroxide pressure oxidation pretreatment resulted in much lower sulphur and carbon oxidation, it gave pretreated residues with decreased levels of preg-robbing activities and higher gold recoveries during subsequent cyanidation, thus indicating some deactivation of the preg-robbing carbon during pretreatment with hydrogen peroxide. The refractoriness due to carbon preg-robbing activity was found to contribute more to the refractory behaviour of the concentrate than the occlusion of gold particles by the sulphide mineralization.
Keywords: Gold concentrate, Oxidation, Mineral processing, Pressure oxidation, Double-refractory concentrate, Hydrometallurgy.