Kinetic and mass transfer analyses of metal biosorption by Caulerpa lentillifera

This study examined kinetics and mass transfer in the biosorption of heavy metals onto Caulerpa lentillifera. The sorption capacity of Cu(2+), Pb(2+) and Cd(2+) from aqueous solution increased with initial metal concentration and decreased with biosorbent dose. Kinetic data were well described using the pseudo-second-order model. Results showed that both external mass transfer and intraparticle diffusion were rate limiting steps in the biosorption process. Activation energy of biosorption kinetics fell in the range of 313 kJ/mol. The biosorption of Cu(2+), Cd(2+) and Pb(2+) on the biomass correlated well with the Langmuir isotherm (R(2)> 0.99) with maximum sorption capacities at 293 K of 0.169, 0.085 and 0.177 mol/kg for Cu(2+), Cd(2+) and Pb(2+) ions, respectively. Thermodynamic studies demonstrated that the biosorption process was spontaneous and endothermic under conditions. The results were analyzed to determine external mass transfer coefficient which was proved to be related to the rate constant of Langmuirian kinetic model. (C) 2011 Elsevier B.V. All rights reserved.