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Equilibrium and Kinetic Studies of Cu (II), Cd (II), Pb (II) and Fe (II) Adsorption from Aqueous Solution Using Cocoa ( Theobroma cacao  ) Pod Husk
OBIKE, AI; IGWE, JC; EMERUWA, CN & UWAKWE, KJ
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
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