Biosorption of cadmium (ii) ion from aqueous solution by Afzelia africana

Abstract

The batch adsorption of cadmium (II) ion from aqueous solution using low-cost adsorbent of biological origin, Afzelia africana shell under different experimental conditions was investigated in this study. The influences of initial Cd (II) ion concentration, initial pH, contact times and temperature were reported. Adsorption of Cd (II) was found to be pH dependent and the results indicate that the optimum pH for its removal from aqueous solution was 5. No marginal effect on the biosorption of cadmium was detected for temperatures between 298 and 313K as observed from their Langmuir isotherm constants (q_max) at different temperatures. q_max values obtained at the different temperatures of 298, 303 and 313K were 13.59, 14.04 and 14.27 mg g^-1, respectively. The adsorption equilibrium shows that the process followed both Freundlich and Langmuir models with Freundlich giving a better fit for the adsorption data in comparison to the Langmuir model. The fit of the adsorption data into Freundlich model shows that the adsorption process was predominantly a physisorption. The results reveal that cadmium (ll) was considerably adsorbed on the A. africana shell and could serve as an economical method for the removal of cadmium from aqueous solutions.

Keywords: Adsorption isotherms, adsorption kinetics, Afzelia africana, biosorbent, biosorption.

African Journal of Biotechnology Vol. 12(32), pp. 5060-5068