Oil Extraction from Castor Cake Using Ethanol: Kinetics and Thermodynamics

In this study, the kinetics and thermodynamics of oil extraction from castor cake using ethanol were investigated. Castor cake had a total oil content of 14.78 +/- 0.12% in mass and the average particle diameter was 0.446 mm. Oil extractions were carried out in a stirred batch extractor system at various temperatures (20, 30, 40, and 55 degrees C). The fit of three different kinetic models to the experimental data was tested, with a modified Fick's Law model being the most appropriate to describe the extraction kinetics (r(2) >= 0.960 and ARE <= 3.25%). Effective diffusion coefficients were determined, ranging from 4.52 x 10(-13) m(2) s(-1) at 20 degrees C to 5.60 x 10(-13) m(2) s(-1) at 55 degrees C. Change in Gibbs' free energy (Delta G degrees) was determined to be negative (-4.55 kJ mol(-1) at 20 degrees C to -6.56 kJ mol(-1) at 55 degrees C), while changes in enthalpy (Delta H degrees) and entropy (Delta S degrees) were positive (12.27 kJ mol(-1) and 57.41 J mol(-1) K-1, respectively).