Abstract

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The kinetics of the removal of manganese cadmium and lead in aqueous solution using cocoa shell as an adsorbent was investigated. The effect of contact time, kinetic of sorption mechanism and the adsorbate concentrations on sorption of Mn2+, Cd2+ and Pb2+ ions were examined. The kinetic of the sorption mechanism of Mn2+, Cd2+ and Pb2+ was evaluated using pseudo-first order (Lagergren) rate and the pseudo-second (Ho-model) rate model. The rate limiting sorption step was physisorption and results indicate that pseudo-second order model provides a more appropriate description of the adsorption rate for the metals ions sorption in cocoa shell. The maximum adsorption capacities per unit gram of the adsorbent at equilibrium time, neutral pH, 200 r p m, and temperature of 25 0C are 9.02 to 40.04 mg kg-1 for Mn2+, 7.02 to 25.89 mg kg-1 for Cd2+ and 5.25 to 11.01 for Pb2+ under 10 to 50 mg kg-1 initial metal concentration. Sorption equilibrium isotherm was determined and correlated with Langmuir and Freundlich model. It was found that the Freudlich adsorption model best fitted the isotherm data. It is concluded that cocoa shell can be use as an effective adsorbent for removal of heavy metals from aqueous solution.

Keywords: Kinetics Cadmium, Manganese, Lead, cocoa shell, sorption.