Indian Journal of Science and Technology Vol. 4 No. 5

Different kinds of low cost agro based fibres can be used to remove both trace and heavy metals from aqueous solutions. The removal efficiency of maize (Zea mays) cob, sawdust and coal was investigated in this study for the bioremediation of nickel and cadmium. Sorption experiments were carried out using batch process and changes in concentration of the adsorbates were monitored by the use of Shimadzu AA650 double beam atomic absorption/flame spectrophotometer. Effects of varying adsorbent dose, adsorbate loading concentration, pH and adsorbent surface area on the percentage removal of the adsorbates were studied. Results revealed that maize cob have higher affinity for Cd than Ni, while the reverse was the case with sawdust and coal, where Ni was found to have higher percentage removal than Cd. Thermodynamic parameters such as ?H and ?S were calculated from Van�t Hoff plots which subsequently lead to the computation of ?G. At 60 mg/L adsorbate concentrations, the adsorption process was found to be endothermic, spontaneous and feasible. The enthalpy, entropy and Gibbs energy changes for the removal of Ni onto maize cob were higher than those of Cd and the opposite scenario was observed for sawdust and coal.