Kinetics and thermodynamics adsorption of carotenoids and chlorophylls in rice bran oil bleaching

• Carotenoids and chlorophylls were absorbed from rice bran oil in the bleaching step.
• Pigments adsorption kinetics was described by pseudo-second order model.
• Freundlich and Langmuir models were evaluated in the equilibrium study.
• The thermodynamic parameters were obtained in the industrial temperature range.
• The rice oil bleaching process was endothermic, favorable and spontaneous.

The adsorption characteristics of carotenoids and chlorophylls in the rice bran oil bleaching at different temperatures (100–120 °C) and activated earth concentrations (0.5–2.5% w/w) were investigated. The kinetic study showed that, after 20 min the adsorption capacity tends to stay constant. Pseudo-second order model was more appropriate to describe the adsorption kinetics for both pigments, especially at higher temperatures. The use of 1% (w/w) of activated earth at 120 °C led to a high decrease in chlorophyll content, while the decrease in carotenoids content was less pronounced. Freundlich model was suitable to represent the equilibrium experimental data for the pigments. The activation energy values showed that the chlorophyll molecules required more energy to be removed from the oil. The rice bran oil bleaching was considered an endothermic, favorable and spontaneous process, and the isosteric heat of adsorption indicated that the activated surface of the earth was heterogeneous.