Combined bio-hydrometallurgical process for gold recovery from refractory stibnite

The aim of this work concerns the recovery of gold by a combined biometallurgical and hydrometallurgical treatment. The biooxidation of a refractory gold-bearing stibnite (antimony sulphide) favours the increase of gold recovery during the subsequent hydrometallurgical process (cyanidation, adsorption onto activated carbon, desorption from activated carbon and electrowinning).Tests were conducted at laboratory scale utilising a refractory stibnite ore. The gold content of the sample was 32 g/t Au. Bacterial cultures utilised in the biological test consisted predominantly of Thiobacillus genus. After a long leach time (24 hours) low recovery was obtained by direct cyanidation (less than 4% Au), while a gold extraction yield of about 80% was achieved combining biometallurgical and hydrometallurgical process.Experimental results have shown the technical feasibility of the biometallurgical pretreatment prior to the hydrometallurgical process. A complete process flow-sheet has been outlined.