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 °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 (<i>r</i>² ≥ 0.960 and ARE ≤ 3.25%). Effective diffusion coefficients were determined, ranging from 4.52 × 10^–13 m² s^–1 at 20 °C to 5.60 × 10^–13 m² s^–1 at 55 °C. Change in Gibbs’ free energy (Δ<i>G</i>°) was determined to be negative (−4.55 kJ mol^–1 at 20 °C to −6.56 kJ mol^–1 at 55 °C), while changes in enthalpy (Δ<i>H</i>°) and entropy (Δ<i>S</i>°) were positive (12.27 kJ mol^–1 and 57.41 J mol^–1 K^–1, respectively)