A composite membrane from 2-hydroxyethyl methacrylate (HEMA) and poly(hydroxyethyl methacrylate)/chitosan (pHEMA/chitosan) was synthesized via UV initiated photo-polymerization in the presence of an initiator alpha,alpha'-azoisobutyronitrile (AIBN). Procion Brown MX 5BR was then covalently immobilized onto composite membrane as a dye-ligand. The binding characteristics of a model protein (i.e. lysozyme) to the dye-ligand immobilized affinity membrane have been investigated from aqueous solution using the plain composite membrane as a control system. The experimental data was analyzed using two adsorption kinetic models, the pseudo-first-order and the pseudo-second-order, to determine the best-fit equation for the adsorption of lysozyme onto affinity composite membrane. The second-order equation for the adsorption of lysozyme on the dye-ligand membrane systems is the most appropriate equation to predict the adsorption capacity for the affinity membrane. The reversible lysozyme adsorption on the affinity membrane obeyed the Freundlich isotherm. The lysozyme adsorption capacity of the plain membrane and the dye-ligand affinity membrane were 8.3 and 121.5 mg ml(-1), respectively. (C) 2002 Elsevier Science B.V. All rights reserved.