title: The influence of the degree of cross-linking on the adsorption properties of chitosan beads.
abstract: The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pKa varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (Kads) and to a lesser extent the adsorbent adsorption capacity (qmax) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0mmol/g chitosan and (9-90)x10(-4), respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (Deff) was determined as (8.0-25.8)x10(-11)m2/s. It was found that Deff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.
authors.affiliation: Department of Chemical Engineering, Vaal University of Technology, Private Bag X021, Vanderbijlpark, Guateng 1900, South Africa. petero@vut.ac.za
authors.forename: Peter O
authors.initials: PO
authors.lastname: Osifo
authors.forename: Athena
authors.initials: A
authors.lastname: Webster
authors.forename: Hein
authors.initials: H
authors.lastname: van der Merwe
authors.forename: Hein W J P
authors.initials: HW
authors.lastname: Neomagus
authors.forename: Marius A
authors.initials: MA
authors.lastname: van der Gun
authors.forename: David M
authors.initials: DM
authors.lastname: Grant
mesh_terms: D000327:Adsorption; D048271:Chitosan / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics
chemical_list: D003300:Copper; D048271:Chitosan