The kinetics and thermodynamics of hempseed oil extraction by n-hexane

Abstract

The influence of extraction temperature and seed-to-solvent ratio in the ranges of 20–70°C and 1:3–1:10g/mL, respectively on the hempseed oil extraction by n-hexane was investigated in order to conduct both kinetic and thermodynamic analysis. For the kinetic modeling, it was assumed that washing and diffusion occurred simultaneously. A four-parameter phenomenological model fitted the experimental data with a mean relative percent deviation (MRPD) of ±2.5% (based on 125 data). The extraction conditions did not influence the fraction of washable hempseed oil (f=0.821±0.006), but affected the washing and diffusion rate constants. A modified Arrhenius equation was used to correlate the rate constants with extraction temperature and solvent-to-seed ratio. Since the washing rate constant was much higher than the diffusion rate constant, the kinetics of the hempseed oil extraction could be successfully described by a simpler three-parameter model based on the assumption of instantaneous washing followed by diffusion (MRPD=±2.8%). The hempseed oil extraction was shown by a thermodynamical analysis to be feasible, spontaneous, endothermic and irreversible. Depending on the seed-to-solvent ratio, the hempseed oil yield increased by a factor of 1.012–1.027 for every 10°C rise in temperature.