Lead (II) removal from aqueous solution by chitosan flake modified with citric acid via crosslinking with glutaraldehyde

BACKGROUNDChitosan flake is a bio-adsorbent that has been studied for adsorption of lead. However, its adsorption capacity for lead was low. To enhance its adsorption capacity, chitosan flakes were modified with citric acid by crosslinking with glutaraldehyde to supplement the functional groups with high affinity for Pb(II) ions. RESULTSModified chitosan flakes with citric were prepared with maximum capacity for Pb(II) of 101.7mg g(-1) at 303K, pH 5, and 300min contact time. The experimental data were used to fit kinetic and isotherm models. The results show that the adsorption of Pb(II) on modified chitosan flake followed a pseudo-second-order model, and the rate of adsorption was controlled by the mass transport mechanism and intraparticle diffusion. In an equilibrium study, it was found that the Langmuir and Freundlich isotherm models were appropriate to describe the adsorption process, indicating a chemisorption process of Pb(II) on the modified chitosan flake. The negative value of the free energy (G) and the positive values of the enthalpy (H) and entropy (S) indicated an endothermic and spontaneous adsorption process of lead (II) on citric acid grafted chitosan flakes (C-Gch). CONCLUSIONChitosan flake modified with citric acid by crosslinking with glutaraldehyde remarkably enhanced the adsorption capacity for Pb(II) ions. This material could be used as an effective adsorbent for the removal of Pb(II) from wastewater and contaminated water sources. (c) 2012 Society of Chemical Industry