Biooxidation of gold-bearing sulphide ores: gold recovery by two leaching treatments

This paper deals with gold extraction from a refractory sulphide ore from a Cuban deposit. The ore was pretreated by bioleaching in order to enhance gold recovery by subsequent chemical leaching. Inoculum age was found not to influence the iron dissolution during bioleaching of the ore. Cyanidation and thiosulphate leaching were tested as an example of gold extraction technology. Conventional operation (cyanidation) was compared with an alternative technology (thiosulphate leaching), which is preferable in regard to environmental impact. Biooxidation pretreatment was effective, enhancing gold extraction yields from about 40% to about 80%, after completion of the treatment circuit (biooxidation-leaching). Gold recovery was thus clearly enhanced by the bioleaching pre-treatment. Thiosulphate leaching was more effective in gold extraction and faster than cyanidation. This preliminary study demonstrates the technical feasibility of extracting gold from a refractory ore with low impact on the environment. Additional experiments are needed to optimize the process in terms of gold recovery from the ore and further minimization of environmental pollution.