Sorption of Cd(II) and Pb(II) from aqueous solutions onto Agave americana fibers

The potential of Agave americana fibers as biosorbent was investigated in batch Pb(II) and Cd(II) removal as a function of pH, initial metal concentration and temperature. Metal sorption followed pseudo-second-order kinetics with excellent correlation. The Langmuir model was successfully applied to describe the sorption isotherms. Under optimum conditions (20 degrees C, pH 5.0, contact time of 30-60 min and 5 g L-1 biomass concentration), the maximum sorption capacity of A. americana fibers was 40.0 mg g(-1) for Pb and 12.5 mg g(-1) for Cd, respectively. The results obtained at different temperatures allowed estimating the thermodynamic parameters (Delta G degrees, Delta H degrees and Delta S degrees) from the sorption equilibrium constants. The positive Delta H degrees value obtained for sorption of both metals indicates the endothermic nature of the process. A. americana fibers were also analyzed by IR-FT spectroscopy and scanning electron and metallographic microscopy, with the aim of investigating the interactions of biomass functional groups with cations and evaluating the mechanisms involved in metal sorption. (C) 2010 Elsevier B.V. All rights reserved.