Effects of Maturity of Coconut Shells on Gold Adsorption Efficiencies of Derived Activated Carbons

Abstract

Coconut shells are used as precursors for preparation of activated carbons. The shells could vary in terms of their maturity. The influence of the maturity of the shells on gold adsorption efficiencies of derived activated carbons (ACs) from gold di-cyanide solution was investigated. The shells were pyrolysed at 900 ºC and the resulting chars were activated in steam at the same temperature for different durations. Assessment of the properties of the derived ACs revealed that; the hardness, gold adsorption capacities and rates of gold adsorption of the ACs depended on the maturity of the shells. The more matured the shells the harder the AC. The relative hardness and gold adsorption rates of the mature coconut shells activated carbons, H_M and R_M, respectively and those of the less mature shells, H_L and R_L, respectively were in the order of H_M >H_L and R_M >R_L. The relative hardness of the ACs derived from the more mature and less mature shells after 3 h activation were 99.3% and 94.0%, respectively and the gold adsorption rates were 5.78 mg Au h^-1 g^-1 and 4.95 mg Au h^-1g^-1, respectively. The adsorption rates and relative hardness depended on the duration of activation, where longer activation times resulted in increase in the adsorption rates and a decrease in relative hardness of the derived ACs.