Oil Extraction from Castor Cake Using Ethanol: Kinetics and Thermodynamics

Abstract

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 (r2 ≥ 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 (ΔG°) 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 (ΔH°) and entropy (ΔS°) were positive (12.27 kJ mol–1 and 57.41 J mol–1 K–1, respectively).