Adsorption characteristics of Pb(II) from aqueous solution onto a natural biosorbent, fallen Cinnamomum camphora leaves

The present work helped in identifying a new low-cost adsorbent, fallen Cinnamomum camphora leaves (FCCL) for effective removal of Pb(II) from aqueous solutions. The adsorption kinetic experiments reveal Pb (II) adsorption onto FCCL follows pseudo-second order kinetics and is mainly controlled by the film diffusion mechanism, which becomes more prominent with increasing initial lead concentration. All equilibrium data obtained at different temperatures fit perfectly with Langmuir isotherm model compared to Freundlich and D-R isotherm models, and the maximum adsorption capacities of Pb(II) adsorbed onto FCCL are 73.15, 73.58, 74.13 and 75.82 mg g(-1) at 303.2, 313.2, 323.2 and 333.2 K, respectively. The analysis for variations of FT-IR spectra, the values of the mean free energies of adsorption (Ea) and the Gibbs free energy (Delta G(0)) all demonstrate that the ion exchange and surface complexation models should both be the dominating adsorption mechanism during the adsorption process. The higher initial lead concentrations and temperatures are both more conducive to the enhancement of surface complexation mechanism compared to ion-exchange mechanism. (C) 2010 Elsevier B.V. All rights reserved.