Removal of copper and cadmium from the aqueous solutions by activated carbon derived from Ceiba pentandra hulls

Activated carbon prepared from Ceiba pentandra hulls, an agricultural solid waste by-product, for the removal of copper and cadmium from aqueous solutions has been studied. Parameters such as equilibrium time, effect of pH and adsorbent dose on removal were studied. The adsorbent exhibited good sorption potential for copper and cadmium at pH 6.0. C=O and S=O functional groups present on the carbon surface were the adsorption sites to remove metal ions from solution. The experimental data was analysed by both Freundlich and Langmuir isotherm models. The maximum adsorption capacity of copper and cadmium was calculated from Langmuir isotherm and found to be 20.8 and 19.5 mg/g, respectively. The sorption kinetics of the copper and cadmium have been analysed by Lagergren pseudo-first-order and pseudo-second-order kinetic models. The desorption studies were carried out using dilute hydrochloric acid solution and the effect of HCl concentration on desorption was also studied. Maximum desorption of 90% for copper and 88% for cadmium occurred with 0.2 M HCl. (c) 2005 Elsevier B.V. All rights reserved.