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The prospects for an alternative gold leach reagent: Thiourea

2000-10-18
Orgul, S
Atalay, U
Gold has been traditionally extracted from ores by leaching with an alkaline cyanide solution. However, certain characteristics and drawbacks of cyanidation process have stimulated research into alternative processes. A number of non-cyanide reagents have been tried for the dissolution of gold. Among them, thiourea leaching seems to be a promising process. This study was carried out on a finely disseminated Kaymaz gold ore (4 g/t Au). The effect of various leaching parameters such as concentration of thiourea, concentration of ferric sulphate, molar ratio of ferric sulphate/ thiourea, leaching duration, temperature and pulp density are studied. The investigations indicated that at room temperature with 16.04 kg/ton consumption of thiourea at pH of 1.35, it was possible to obtain a gold extraction of 85.8 % for the particle size of 80 % passing 53 micron feed in 6 hours. Staged addition of chemical reagents, pretreatment of ore by acid washing and microwave heating were also tested in accordance with lowering the thiourea consumption.