Kinetics and thermodynamics of oil extraction from South African hass avocados using hexane as a solvent

Abstract

This study evaluated the yield, kinetic and thermodynamics parameters of the oil extraction process from South African Hass Avocados using Hexane as a solvent. The avocado oil was extracted through the solid-liquid process at different temperatures. The thermodynamic parameters that were evaluated and modelled in this study were studied under constant volume, pressure and temperature conditions during extraction experiments. The enthalpy, entropy and Gibbs free energy were the parameters studied. The extraction was done at four different temperatures 40 °C, 50 °C, 60 °C and 70 °C. The kinetic model found that the extraction reaction was first-order reaction and the increase in temperature increased the oil yield from 169.20 g/L at 40 °C to 210.73 g/L at 70 °C after 3 h of extraction. The activation energy found was Ea = 127.30 KJ/mol, the thermodynamic parameters under the transition theory at 70 °C were ∆S≠ = 70.06 J/mol.K, ∆H≠ = 124.44 KJ/mol, ∆G≠ = -23.91 KJ/mol. The standard thermodynamic parameters of the process at 70 °C were ∆H = 0.09 KJ/mol, ∆S = 70.06 J/mol.K and ∆G = -7.19 KJ/mol. These indicated that the extraction of avocado oil is an irreversible reaction and the reaction is endothermic. Furthermore, it was proven that the reaction is spontaneous.