Equilibrium, kinetics, and thermodynamic of adsorption of enzymes on diatomite clay materials

Abstract

In adsorption experiments, enzymes and diatomite clay minerals that have been used lately are of great importance due to their biological and physicochemical properties. For this purpose, in this study, the adsorption and kinetic parameters of lipase enzyme on diatomite clay were investigated. The diatomite and the lipase enzyme were characterized by SEM, TGA, FTIR, etc. The effect of adsorption kinetic parameters such as pH (from 5.5 to 9), initial of enzyme concentration (0.10-0.35gL(-1)), temperature (288-318K), and ionic strength (1.10(-3)-7.5.10(-3)molL(-1)) was investigated, and obtained optimum conditions for the maximum adsorption capacity of diatomite clay were found to be pH7, temperature of 36.5 degrees C, and ionic strength of 0.35gL(-1). The kinetic data obtained from experimental studies were investigated using different kinetic models that are pseudo-first-order, pseudo-second-order, and intra-particle diffusion. The results showed the second-order equation was found to be the best kinetic model for the adsorption process. The activation parameters such as E-a, enthalpy (H), Gibbs free energy (G), and entropy (S) were calculated. The activation parameter results showed that the interaction between diatomite clay and lipase enzyme is a physical interaction and their adsorption process is exothermic. These results indicated that diatomite clay could be used as an adsorbent for the adsorption of lipase on diatomite.