Ultrasound-assisted bleaching of olive oil: Kinetics, isotherms and thermodynamics

Experimental data of the adsorption of carotenoids and chlorophylls were investigated to obtain adsorption kinetic, isotherm and thermodynamic information during ultrasound-assisted bleaching (US bleaching) of olive oil and to compare them with the results from conventional bleaching method. Adsorption of pigments on activated bentonite was rather fast and efficient by applying ultrasound. In both bleaching procedures, the kinetics of carotenoids adsorption followed pseudo-first order model whereas pseudo-second order equation gave a better fit to the adsorption of chlorophylls. It is speculated that adsorption of carotenoids is mainly facilitated by physisorption while chemical reactions are also involved in the removal of chlorophyll pigments under sonication. Equilibrium study shows that the adsorption behavior of the two pigments is different. Freundlich isotherm provided accurate estimates of adsorption equilibrium data of chlorophylls during US bleaching indicating a multilayer adsorption under ultrasound irradiation. According to the thermodynamic analysis, both bleaching methods are endothermic and spontaneous with increased randomness at the solid-liquid interface.