The adsorption of gold and copper onto ion-exchange resins from ammoniacal thiosulfate solutions

The recovery of gold and copper from ammonium thiosulfate (ATS) solutions using anion-exchange resins has been investigated using batch studies. Strongly basic resins are preferred to weakly basic resins because of their greater range of operational pH and higher loading. The kinetics and isotherms for the adsorption of gold and copper were measured. Individually, gold and copper could be loaded onto resins at high concentrations. The presence of copper was found to greatly lower the stability of the ammonium thiosulfate solution due to copper-catalyzed thiosulfate oxidation and formation of copper sulfides or hydroxides, depending on the conditions. Tetrathionate, as the product of thiosulfate oxidation, strongly poisoned the resins. The effect of thiosulfate and ammonia concentrations on the adsorption was also studied. In the simultaneous loading, good selectivity for gold over copper was obtained. The metals were eluted with a mixed solution of Na2SO3 and NH3.