Application of Coconut Copra as Biosorbent for Removal of Heavy Metals

Abstract

Previous studies have evidenced that coconut copra is a potential biosorbent for removal of dissolved organic carbon from peat swamp runoff attaining an average removal of 96 %. The capability of coconut copra in removing heavy metals including cadmium (Cd), chromium (Cr) and nickel (Ni) is scarcely reported. In this paper, response surface methodology was applied to evaluate the optimum conditions for removal of Cd, Cr and Ni from aqueous solution using raw coconut copra. Batch adsorption experiments were conducted according to inscribed central composite design. Response surface models further identified the optimum dosage, pH and contact time for Cd removal is 1.5 g, pH 11 and 60 min, Cr removal is 0.1 g, pH 8.48 and 60 min while Ni removal is 0.1 g, pH 11 and 15 min. Bimodality is observed in response surface graphs, implying the possible existence of two equilibrium phase during the adsorption process. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were employed to describe the adsorption behaviour. Results revealed that raw coconut copra can remove 4.55 mg/g of Cd, 8.71 mg/g of Cr and 26.46 mg/g of Ni. The adsorption processes are physical adsorption.