Extraction of oil from Terminalia catappa L.: Process parameter impacts, kinetics, and thermodynamics

• Temperature and time increment increases the oil yield of Terminalia catappa Kernel (TCK). Oil yield was obtained with the smallest particle size.
• N-hexane was the best solvent for TCK oil extraction compared to the other solvents (benzene, chloroform, ethanol, and petroleum ether).
• Evaluated physicochemical characteristics (dielectric strength, density, viscosity, and acidity) of TCK oil indicated its potential application industrially as transformer oil. The fatty acid composition indicated that the oil was unsaturated.
• The three kinetic models (pseudo second order, hyperbolic and Elovich) evaluated gave good fit to the extraction kinetic data obtained experimentally.
• The ΔG, ΔS, and ΔH values obtained indicated that the extraction process was spontaneous, irreversible, and endothermic, respectively.

The effects of temperature, time, solvent type, and particle size on oil yield as well as the effects of these parameters (particle size, time, and temperature) on the kinetics and thermodynamics parameters (enthalpy, entropy, and free energy) of oil extraction from Terminalia catappa L. kernel (TCK) were investigated. Among the different extractions solvents examined, n-hexane gave the highest oil yield of 60.45% (by weight) at 55 °C, 150 min, and 0.5 mm particle size. Findings from the physicochemical properties investigation revealed that the viscosity, acidity, and dielectric strength of the TCK oil were 20.29 mm2 s−1, 4.73 mg KOH/g oil, and 30.61 kV, suggesting the potential suitability of TCK oil as transformer oil. Analysis of the chemical composition of the TCK oil indicated that it is composed of 43.89% and 56.1% saturated and unsaturated fatty acids, respectively. The kinetics of the TCK oil extraction was better described by the pseudo second order model compared to hyperbolic and Elovich models. The ΔG, ΔS, and ΔH values of the TCK oil extraction process were −28.76 kJ/mol, 0.643 kJ/mol, and 182.81 kJ/mol, respectively, indicating spontaneous, irreversible, and endothermic process.