REMOVAL OF CYANIDE FROM SOLUTION USING ACTIVATED CARBON

The level of cyanide in plant tailing is pertinent when considering the use of tailings for underground backfilling operations. Activated carbon is known to act both as an adsorbent and as a catalyst for the oxidation of cyanide. In the present study, activated carbon was found to enhance the removal of cyanide, mainly as HCN from aqueous solutions at pH values of 7 and lower. Enhanced rates of cyanide loss from pH 10 solutions are achieved by the use of softer activated carbons, or by the use of a higher degree of attrition, which exposes freshly-cleaved carbon faces to the cyanide solution. Cyanide is removed most efficiently from alkaline solutions and pulps by use of copper-impregnated activated carbon. Copper(I) and copper(II) were found to catalyze the oxidation of cyanide by activated carbon and also to result in an increase in cyanide adsorption capacity. The adsorbed cyanide may be recovered from the loaded carbon with dilute acid. Existing CIP or CIL flowsheets may be adapted to take advantage of these effects, resulting in a simple, effective means for the removal of the bulk of the cyanide reporting to gold-plant tailings.