Equilibrium and kinetic studies of Cu (II), Cd (II), Pb (II) and Fe (II) adsorption from aqueous solution using cocoa (<i>Theobroma cacao</i>) pod husk

Abstract

The potentials of cocoa pod husk to adsorb Cu (II), Cd (II), Pb (II) and Fe (II) ions from aqueous solutions was investigated in a batch system. The effects of contact time, initial metal ion concentration and adsorbent dose on the adsorption capacity of the adsorbent were examined. The percent adsorbed increased as initial metal ion concentration, contact time and adsorbent dose was increased until equilibrium was reached. Langmuir isotherm and pseudo-second order models were used to analyse the equilibrium and kinetic experimental data respectively. Equilibrium experimental data of Cu (II), Cd (II), Pb (II) and Fe (II) adsorption onto cocoa pod fitted well to Langmuir model and the kinetic data also fitted well to the pseudo-second order model, as indicated by the correlation coefficients. The maximum sorption capacity (qmax) ranged as 4.16, 4.42, 4.69 and 4.83 mg/g for Fe (II), Cd (II), Cu (II) and Pb (II) respectively. This study demonstrated that the waste cocoa pod could be used as a potential adsorbent for toxic metals such as Cu (II), Cd (II), Pb (II) and Fe (II).

Keywords: Adsorption isotherm, Adsorption Kinetic, Cocoa pod, Langmuir isotherm, Pseudo-second order model