LEACHING AND RECOVERY OF COLD IN THIOSULFATE BASED SYSTEM - A RESEARCH SUMMARY AT ICM

Research at ICM on gold leaching and recovery related to thiosulfate s ystem is briefed. Ammonia was found to promote the thiosulfate leachin g of gold by preferential adsorption on the gold surface and dissoluti on of gold as an auroammine intermediate which then converts into thio sulfate complex. This will prevent sulfur species from adsorption on g old, resulting to form sulfur and sulfide passivation coating on its s urface. Thiosulfate needed for gold leaching can be produced at the pl ant site by PTC disporportionation of elemental sulfur to mixed polysu lphide and thiosulfate, followed by oxidation of the fresh polysulphid e to thiosulfate with aeration. Solvent extraction of gold in thiosulf ate solutions with neutral phosphorus esters, amines and their mixture s was also investigated.