Kinetic Model for the Decomposition of Cyanide during the Elution of Gold from Activated Carbon

Abstract

Abstract Free cyanide is usually present during the elution of gold cyanide from activated carbon. The decomposition of cyanide is important not only in the extraction of gold but also for environmental reasons. Previous studies have indicated that competitive adsorption of cyanide with aurocyanide plays a minor role at the elevated temperatures used in industry. A more important effect of cyanide is its decomposition reaction with functional groups on the carbon, the products of which passivate the surface for adsorption of aurocyanide, and thereby cyanide appears to enhance the elution of aurocyanide. It was observed that the degree of passivation affects the elution of gold and the degradation/adsorption of cyanide itself. Batch tests have shown that the rate of oxidation of cyanide at low temperatures is independent of particle size and more dependent on film transfer. Based on these observations, a kinetic model was proposed for the decomposition and elution of cyanide in packed columns of activated ...