Abstract
Thiosulfate (TS) process for extraction of gold and silver is a promising alternative to the highly toxic cyanidation process. One of the main reasons caused limiting the practical application of the TS process is the poor recovery of gold and silver on the commonly used activated carbon (AC). Increasing amounts of TS ions greatly inhibited the adsorption of gold and silver from synthetic solutions. No adsorption was obtained when the TS concentration reached 0.8 M after 5 h. The adsorption efficiency from real leach liquor initially contained 0.2 M TS was as low as 40-50%, after a long time of 15 hours. We have suggested that the removal of the residual TS ions in leach liquor through an interaction with an oxidizing agent such as ammonium persulfate (APS) would improve the adsorption of gold and silver on AC. Increasing the APS concentrations from 0.0 M to 0.01 M drastically improved the gold adsorption efficiency from 5% to 85% after only 10 min. Almost 95% of both metals was adsorbed after 90 min. EDXRF chart confirmed the adsorption of gold and silver on AC. A process flowsheet was proposed for an integrated TS leaching and recovery of gold and silver from Al Amar tailing including adsorption on AC in presence of APS.