Adsorption isotherm, thermodynamics and kinetics studies of polyphenols separation from kiwifruit juice using adsorbent resin

In this study, the adsorption characteristics of polyphenols in kiwifruit juice were investigated using AB-8 resin, with the aim to separate the poiyphenols from kiwifruit juice to prevent astringency and browning during processing and storage. Results showed that the adsorption ability (q(e)) of the resin increased with an increase in temperature. The adsorption equilibrium was best described by the Freundlich isotherm (R-2 > 0.98). Thermodynamic parameters including the changes of enthalpy (triangle H), free energy (triangle G), and entropy (triangle S) were evaluated at 25, 30 and 35 degrees C. From the enthalpy change (0 < triangle H < 5), the adsorption was endothermic in nature and involved physical adsorption. The result of free energy change (triangle G < 0) deinonstrated a spontaneous adsorption process. The pseudo first-order model was found to describe the kinetic data satisfactory. The adsorption mechanism was not limited solely by intra-particle diffusion as shown by the Weber and Morris model. (C) 2012 Elsevier Ltd. All rights reserved.