Improved recovery of gold and silver from thiosulfate solution on activated carbon in presence of ammonium persulfate
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Taif University
Mohamed Mahmoud   

Taif University
Publication date: 2019-08-26
Physicochem. Probl. Miner. Process. 2019;55(5):1271–1285
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.‎