Comparison of activated carbon and ion-exchange resins in recovering copper from cyanide leach solutions

The use of activated carbon and ion-exchange resins for recovering copper cyanide from gold leach solutions is compared in detail. When using activated carbon, the overall cyanide-to-copper ratio should be reduced to ∼ 2 to achieve the most effective adsorption. This can be accomplished by dissolving metallic copper into the leach solution. However when using ion-exchange resins to recover the copper, it is not necessary to reduce the overall cyanide-to-copper ratio as the Cu(CN)32− complex, which is most prevalent in leach solutions, can strongly adsorb onto the resin. Whilst the elution of copper from carbon is relatively simple, the elution of copper from the resins is challenging. Among a variety of elution systems investigated, a cyanide soak followed by NaCl elution appears to be the most elegant, with the advantage of no regeneration of the eluted resin being needed. Two closed loop elution flowsheets have been investigated to recover copper from ion-exchange resin, with each having a different impact on the removal of thiocyanate from the leach solution by the resin.