Copper (II), cadmium (II) and lead (II) adsorption kinetics from aqueous metal solutions using chemically modified and unmodified cocoa pod husk (Theobroma cacao) waste biomass

Abstract

The use of thiolated and unmodified cocoa pod husk for the removal of Cu2+, Cd2+ and Pb2+ ions from aqueous solution was studied in this study with respect to adsorption capacity and kinetic studies. Adsorption capacity was rapid as appreciable level of metal ions uptake was achieved at contact time of 10 min and increase in adsorption capacity occurred between 10 and 60 min. Results further showed maximum adsorption capacity of the adsorbents as 97.6057 mg g-1 (Cu2+), 98.8860 mg g-1 (Cd2+) and 99.9454 mg g1 (Pb2+) by the Unmodified Cocoa Pod Husk (UCPH). The trend of the sorption capacity was found to be Pb2+>Cd2+>Cu2+ for both unmodified and modified adsorbents. Thiolation modification decreased the adsorption capacity of the adsorbent. Pseudo second-order kinetic model favoured the adsorption process with R2 = 1 thus giving a better fit than the Pseudo first-order model. Intraparticle diffusion model by Weber and Morris gave a better fit with highest R2 value of 0.9724 and confirmed particle diffusion as the predominant mechanism for the sorption process. © Medwell Journals, 2011.