Kinetic study of immobilized lysozyme on the extrudate-shaped NaY zeolite

The adsorption rate of lysozyme onto the extrudate-shaped NaY zeolite was studied in a reciprocal shaking water bath system and shown to be a function of shaking rate, initial lysozyme concentration, and operating temperature. The initial adsorption rate was mainly dependent on the shaking rate and the equilibrium of adsorption for lysozyme was approached after 30 min. The saturation capacity was found to be 16.43 (mg lysozyme/g zeolite) for an increase in the shaking rate up to 150 rpm. The initial rates increased from 1.987 to 6.260 (mg lysozyme/min g zeolite) with increasing the initial lysozyme concentration from 0.25 to 2.0 (mg lysozyme/ml solution). However, the initial adsorption rate decreased with an increase in temperature. The values of saturation capacity for lysozyme of the zeolite significantly decreased from 35.21 to 14.92 (mg lysozyme/g zeolite) with temperature increasing from 277 to 310 K. Furthermore, the experimental data were analyzed using various kinetic models (i.e. KEKAM, pseudo-first order, and pseudo-second order) to determine the best-fit equation for describing the adsorption behavior. The results showed that the pseudo-second order kinetic equation was the most appropriate to predict the dynamic adsorption behavior of lysozyme on the zeolite. This suggested that the rate-controlling step might be the surface reaction mechanism but not the mass transport to the external surface of the zeolite. Additionally, desorption rate of the immobilized lysozyme on the zeolite in the presence of 1.0 M NaCl was measured at different temperatures (277–310 K). One proposed model was used to predict the experimental desorption data for the elution of the adsorbed lysozyme. The kinetic parameters and activation energy of the desorption process were also determined.