Procion Green H-4G immobilized on a new IPN hydrogel membrane composed of poly(2-hydroxyethylmethacrylate)/chitosan: preparation and its application to the adsorption of lysozyme

The adsorption of lysozyme has been investigated on the Procion Green H-4G immobilized novel poly(2-hydroxyethyl methacrylate)/chitosan) (pHEMA/chitosan; IPN) porous hydrogel membrane. The IPN membranes were prepared by UV initiated photo-polymerization using 2-HEMA and chitosan. The IPN membrane reached an equilibrium swelling within about 60 min. The water content of the dye immobilized membrane was 50±2% and the amount of immobilized Procion Green H-4G on the membrane was 0.678 μmol ml−1. The rates of adsorption of lysozyme on pHEMA/chitosan and pHEMA/chitosan-dye immobilized membranes were measured in a stirred cell. The adsorption capacities of these membranes were determined by changing pH and the concentration of lysozyme in the adsorption medium. The adsorption phenomena appeared to follow a typical Langmuir isotherm. Lysozyme adsorption capacity of the pHEMA/chitosan and pHEMA/chitosan-dye immobilized membranes were 0.18 and 14.06 mg ml−1, respectively. The maximum lysozyme adsorption capacity (qm) of the pHEMA–chitosan-dye immobilized membranes was 20.28 mg ml−1 and the dissociation constant (Kd) value was found to be 1.01 mg ml−1 lysozyme. The experimental data were also analysed using first order Vanʹt Hoff equation for lysozyme-adsorbent interactions, the change in entropy and Gibbs energy of binding were determined at different temperatures and the enthalpy of the system was calculated as 2.5 kcal mol−1. All of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 1.0 M KSNC at pH 8.0.