Adsorption of Cd (II) Ions by Coconut Copra: Isotherm and Regeneration Studies

This study employed coconut copra to adsorb cadmium and investigated its adsorption behavior via isotherm models. A total of seven isotherm models, namely Langmuir, Freundlich, Sips, Temkin, Dubinin-Radushkevic, Brouers-Sotolongo and Hill were utilized to investigate the adsorption mechanism. Results showed that Langmuir isotherm best fitted cadmium adsorption process among all models studied, with correlation coefficient, R2 of 0.963. The maximum adsorption capacity of coconut copra towards cadmium recorded 1.092 mg g−1 according to Langmuir isotherm, Dubinin-Radushkevic and Temkin isotherm asserted that this is a physical adsorption process. This study however observed negative cooperativity, as claimed by Hill and Temkin isotherm models. In addition, this study explored the feasibility of biosorbent regeneration. Coconut copra demonstrated potential to be regenerated, supported by its efficient removal percentage up to 7 consecutive adsorption-desorption cycles. As a whole, coconut copra is potentially viable to be used as a sustainable biosorbent for cadmium removal cadmium.