Thermodynamic properties of water adsorption from orange peels

Orange peels are a promising agroindustry-waste that can be implemented in the extraction and production of pectin, as dietary fiber in food formulations, and as a biopolymer for metal adsorption in water treatment. The present work, therefore, aims to study the adsorption isotherms and the thermodynamic properties of the water adsorbed from orange peels ( C. sinensis cv. Brazilians) at six different temperatures (20, 30, 40, 50, 60 and 70 °C) in the water activity range of 0.020 to 0.853. The GAB model was applied in modeling the experimental adsorption isotherms of orange peels, obtaining statistical values of R 2 = 0.996. Differential and integral thermodynamic properties of water sorption for orange peels were determined by the analytical derivation of the water activity with respect to the temperature from GAB model. Results of the differential thermodynamic properties showed an energetic interaction zone of water molecules with the material. Furthermore, integral thermodynamic properties showed an equilibrium zone controlled by the orange peel enthalpy and entropy. Finally, the orange peel power adsorption information can be used as a point of reference for the controlled process in the different application areas.