Removal of cyanide from aqueous solution using impregnated activated carbon

Impregnated activated carbons are carbonaceous adsorbents which have silver and nickel distributed on their surface. The impregnation optimises the existing properties of the activated carbon giving greater cyanide removal capacity to the carbon. This facilitates the cost-effective removal of cyanide impurities from aqueous effluent. The adsorption isotherms of the impregnating elements (Ag and Ni) from aqueous solutions on plain activated carbon was measured. The amount of adsorbed silver on plain carbon reached 45.7 mg g−1 carbon and for nickel was 4.3 mg g−1 carbon. These impregnated materials were packed in fixed bed columns and used for cyanide removal from aqueous solutions. The adsorbed capacity was monitored from the breakthrough, which indicates that the carbon is not longer adsorbing effectively. The results indicates that carbon–Ag impregnation was shown to have a cyanide removal capacity of nearly two times that of carbon–Ni impregnation and of four times that of plain activated carbon. These suggest that cyanide was probably eliminated in the forms Ag(CN)2− and Ni(CN)4 complexes. However, calcination of impregnated activated carbon under nitrogen at 300°C showed similar results to impregnated non-calcinated ones.