Kinetics and thermodynamics of Cu(II) biosorption on to a novel magnetic chitosan composite bead

Novel chitosan/Fe3O4 composite beads were prepared and used for the removal of Cu(II) ions from aqueous solution. The effect of initial pH, metal ion concentration and temperature on the sorption capacity of the composite was investigated. The kinetics and isotherms of Cu(II) sorption were analysed by the intra-particle diffusion model and the Langmuir, Freundlich and Slips models, respectively. The results showed that diffusion was the rate-limiting step during the whole sorption process. The maximum sorption capacity of the composite chitosan was 121.9 mg/g beads (192.6 mg/g chitosan) at pH 5.0, and the sorption capacity increased with increasing temperature, indicating that the sorption process was endothermic. Thermodynamic parameters such as Gibbs free energy change (Delta G(0)), enthalpy change (Delta H-0) and entropy change (Delta S-0) were also determined. Desorption of the metal ions from the composite chitosan beads was achieved by using 0.05 M EDTA.