Adsorption kinetics and thermodynamics of β-carotene on silica-based adsorbent

The adsorption behaviour of beta-carotene on synthetic adsorbent was studied by batch tests. This study was to develop the adsorption isotherm and thermodynamic aspects of beta-carotene from crude palm oil on native silica. The experiments were studied by employing a spectrophotometer to measure the concentration of beta-carotene before and after adsorption. The effects of various parameters such as contact time, temperature and initial beta-carotene concentration were determined. The adsorption capacity increased with increasing contact time and temperature. Langmuir and Freundlich isotherms were applied to fit the equilibrium data to identify the best isotherm to describe the beta-carotene adsorption. The data were best described by Langmuir isotherm, maximum monolayer adsorption capacity of beta-carotene onto florisil was 86.207 mg/g. Three kinetic models were used to investigate the adsorption mechanism which included pseudo-first-order kinetic, pseudo-second-order kinetic and intraparticle diffusion models. The adsorption followed second-order kinetic model. The data obtained from adsorption isotherm models were used to determine the thermodynamic parameters such as enthalpy change (Delta N). entropy change (Delta S) and free energy change (Delta G). The positive value of Delta H indicated that the adsorption process was endothermic in nature. The negative value of Delta G indicated the spontaneity of the adsorption of beta-carotene on the adsorbents. (C) 2008 Elsevier B.V. All rights reserved.