Kinetics and Isotherm of Heavy Metal Adsorption on Activated Nigerian Coconut Shell and Corn Cob

The performance of activated coconut shell and corn cob as adsorbent for adsorption of iron (II) ion (Fe2+) and nickel (II) ion (Ni2+) from aqueous solution was investigated. Effects of initial metal concentration, temperature, dosage, pH, particle size and contact time on the adsorption was also studied. Adsorption kinetics and isotherms used Adsorption process. Results of the amount of metals removed, increased with increase in adsorbent dosage and contact time, while increase in temperature, initial metal concentration and particle size decreased the adsorption percentage. Fe2+ adsorption reached equilibrium at about 120 minutes, while that of Ni2+ was attained at about 150 minutes in both adsorbents. The adsorbents were more effective in the removal of Fe2+ (up to 83% removal at optimal conditions) than Ni3+ (with up to 67% removal at optimal conditions), while coconut shell slightly outperformed activated corn cob. The second order kinetics fitted better than the first order and the intra-particle diffusion. Hence, the pseudo second order kinetics is most suitable for the adsorption process. Finally, the Langmuir, Freundlich and Temkin isotherms, all showed capability for interpretation of Fe2+ and Ni2+ adsorption onto activated coconut shell and corn cob. Therefore, it is recommended that activated coconut shell and corn cob be used for treatment of industrial effluent before disposal, to reduce environmental contamination.