Effect of Chemical Activation on the Adsorption of Heavy Metals Using Activated Carbons from Waste Materials

The effect of chemical activation on the adsorption of metals ions (Cr2+, Cu2+, Ni2+, Pb2+, Fe2+, and Zn2+) using waste Nigerian based bamboo, coconut shell, and palm kernel shell was investigated. The bamboo, coconut, and palm kernel shell were carbonized at 400°C–500°C and activated at 800°C using six activating agents. Chemical activation had significant effect on the iodine number and invariably increased the micropores and macropores of the activated carbons produced from bamboo, coconut, and palm kernel shell. It also affected the adsorption of metal ions and the type of carboneous material used for activation. The highest metal ions adsorbed were obtained from bamboo activated with HNO3. The cellulose nitrite formed during the activation of bamboo with HNO3 combined with high pore volume and low ash content of bamboo effectively create more reaction sites for adsorption of different metal ions. This shows that waste bamboo activated with HNO3 can effectively be used to remove metal ions from waste streams and in different metal recovery processes than activated carbon from coconut shell and palm kernel shell. 1. Introduction The increased concern by environmentalist and government on the effect of heavy metals and attempt to protect public health gave rise to a lot of research in the development of advance technology to remove heavy metals from water and waste waters. The treatment efforts involved the application of unit processes such as chemical precipitation, coagulation, adsorption, ion exchange, and membrane filtration. Several works on activation of carboneous materials showed that the specific surface area, pore structure, and surface chemical functional groups of porous carbon determined their applications. The pore structure of porous carbon could be controlled by various routes, such as, activation conditions (activation agent, temperature, and time), precursor, templates, and so forth. The surface chemical functional groups are mainly derived from activation process, precursor, heat treatment, and postchemical treatment [1]. Yan and Viraraghavan [2] used different chemicals to study the effect of pretreatment of Mucor rouxii biomass on bioadsorption of Pb2+, Cd2+, Ni2+, and Zn2+. Pretreatment with detergent and alkali chemicals such as NaOH, Na2CO3, and NaHCO3 were found to improve or maintain the bioadsorption capacity in comparison with live M. rouxii biomass. Acid pretreatment using HCl, H2SO4, and C2H4O2 resulted in a significant reduction in the bioadsorption capacity while alkali pretreatment was found to be more effective.