Selective elution of the gold cyanide complex from anion exchange resin using mixed solvents

This study is concerned with the use of mixed solvents for the elution of the cyanide complexes of copper and gold from Purolite A500, a strong-base anion exchange resin. The mixed solvents investigated include acetone + water, dimethylsulfoxide + water and N-methyl-2-pyrrolidone + water. Three types of counterions are employed in each of the mixed solvents: CN−, Cl− and OH−. The effects of counterion concentration and mixed solvent composition on the elution of the complexes are examined. High recoveries of the gold cyanide complex are achieved in the mixed solvents at relatively low counterion concentrations. In contrast, the recoveries of the copper cyanide complexes are 1–3 orders of magnitude lower for the given initial loading of the metals on the resin. The selectivity of the elution process for gold is discussed in terms of the degree of solvation of the various anions in the mixed solvents. The results of this study point to the possibility of using mixed solvents to develop an elution process that is selective for gold over multivalent cyanide complexes.