Adsorption Isotherm Studies of Cd(ll) and Pb(ll) Ions from Aqueous Solutions by Bamboo-Based Activated Charcoal and Bamboo Dust

Abstract

This study investigates a comparative assessment of two adsorbents: Bamboo-based Activated Charcoal (BBAC) and Bamboo dust (BD) in the removal of lead(ll) and cadmium(ll) ions from aqueous solutions. Maximum Pb(II) and Cd(II) removal was observed at pH 6.0. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were applied to the adsorption data. The coefficients of determination of the four models were high with Freundlich model providing the best description for the experimental adsorption data. The fitting of the adsorption data into Freundlich model shows that the mode of adsorption of the metal ions by both adsorbents follows physisorption. Investigation into the maximum adsorption capacity showed that Pb(ll) was better adsorbed than Cd(ll) on both adsorbents. Maximum adsorption capacities corresponding to monolayer coverage, obtained from the Langmuir plots were 4.792 mg g-1 and 4.594 mg g-1 respectively for Pb(ll) and Cd(ll) ions onto the BBAC and 4.771 mg g-1 and 4.400 mg g-1 for their adsorption onto BD. The Langmuir adsorption coefficient, KL which is related to the affinity of the adsorbents for the metal ions were 0.699 and 0.271 respectively for adsorption of Pb(II) and Cd(II) ions onto BBAC and 0.299 and 0.226 for adsorption onto BD following the initial order. The carbonized bamboo based adsorbent was generally found to have an increased adsorption capacity for the metal ions than bamboo dust.