Kinetics and equilibrium of Cu(II) adsorption onto chemically modified orange peel cellulose biosorbents

A series of orange peel cellulose biosorbents has been specifically prepared by different chemical modifications to understand the mechanism of copper adsorption from chloride solutions. The different biosorbents and raw orange peels were characterized using elemental analysis and Fourier transform infrared spectroscopy (FTIR). The acidic and basic sites and pH of zero charge were also determined. The influences of pH, contact time, initial copper concentration and solid/liquid ratio on copper removal were examined. The maximum adsorption capacity of copper was 1.22 mol/kg, using orange peel esterified by 0.6 mol/L citric acid at 80 degrees C after 0.1 mol/L NaOH saponification. A comparison of different isotherm models revealed that the combination of Langmuir and Freundlich (L-F) isotherm model fitted the experimental data best. Results indicate that the chemically modified orange peel cellulose can provide an efficient and cost-effective technology for eliminating copper from aqueous solution. (C) 2008 Elsevier B.V. All rights reserved.