Effects of cysteine and oxygen on recovery of cemented gold from leach liquors in a thiourea system

A study of the combined process of acidothioureation-cementation was carried out at laboratory scale. The test-work material was a natural ore taken from Cimanggu gold occurrence in West Java, Indonesia. Experimental procedures are described. The effects of cysteine and oxygen are of particular interest. Gold concentrations in both raw and treated thiourea solutions are also evaluated. The results of the study reveal that (I) Cysteine is an effective stabilizer for thiourea solutions, but it has a negative effect on the extraction of gold from the ore and on the recovery of cemented gold from the leach solution, (2) In the absence of cysteine, oxygen is required for recovering gold from gold-thiourea complex solutions by the cementation process, and (3) Raw thiourea solutions, as long as there is no sulphur precipitation, along with thiourea solutions treated with aqua regia, can be used for determination of gold.