Effect of magnetite on the adsorption behavior of Pb(II), Cd(II), and Cu(II) in chitosan-based hydrogels

In the present investigation, a chitosan-based hydrogel, graft-copolymerized with methylenebisacrylamide and poly(acrylic acid), (i.e., CS-co-MMB-co-PAA), was employed in studies on the adsorption kinetics of Pb (II), Cd(II), and Cu(II) ions in aqueous solution. Swelling studies performed using the Fickian diffusion model inferred that the mass transfer mechanism of water in hydrogels was governed by diffusion and macromolecular structural relaxation, modified by the presence of magnetite. The best parameters for the removal of metals were pH between 4.5 and 5.5, initial metal concentration of 300 mg dm(-3) and 100 mg of dried hydrogel mass. Isotherm models of Langmuir, Freundlich and Redlich-Peterson suggest that there may be variation in the physicochemical phenomena involving metal adsorption. These isotherms reveal that the adsorption efficiency decreased in the presence of magnetite. Hydrogels with magnetite and the metal ions adsorbed on them may be recovered after the application of an external magnetic field, as opposed to the hydrogels without magnetite, which are frequently recovered using a chemical solvent. The recovery of adsorbents by applying external ac or dc magnetic fields in the absence of solvent is an environmentally clean alternative, with no production of a secondary waste. (C) 2011 Elsevier By. All rights reserved.