The kinetics of oil extraction from olive cake by using ethanol 96% was studied for different solvent-tosolids ratios and temperatures. The thermodynamic aspect of the extraction process was also examined. In the kinetic study, the results produced by the model of So and Macdonald (a model involving two main mechanisms of oil extraction: a washing process and a diffusion process with two stages) were found to be in good agreement with the experimental data. The yield of oil in the extract increased with increasing contact time, solvent-to-solids ratio and extraction temperature. The calculated values of the mass transfer coefficients of various stages of the extraction were found to increase linearly with solvent-to-solids ratio and temperature. In all cases, the predominant mechanism in the extraction was the washing of the oil occurring on the particle surface. The values of the activation energy were 8.56 kJ mol -1 for the washing stage, 9.88 kJ mol -1 for the first stage of diffusion and 17.55 kJ mol -1 for the second stage of diffusion by changing temperature from 20 to 50°C. Further, the results obtained from thermodynamic study of extraction process gave positive values of enthalpy and entropy changes and negative values of change in free energy. Under the equilibrium conditions, the temperature coefficient was found to be 1.02.

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Olive cake is an important solid waste of the olive oil production. It still contains a certain quantity of oil that can be recovered by means of solvent extraction. In this study, two‐level full factorial design was performed to evaluate the effects of four variables and their interactions on the oil extraction by the ethanol 96.0% in a batch reactor. The variables included size of particles, temperature, and time of contact and solvent‐to‐solids ratio. The statistical analysis of the experimental data showed that the extracted oil mass depends on all the examined variables. It also depends on the interactions between size of particles and solvent‐to‐solid ratio and size of particles and temperature. The experimental data were in good agreement with those predicted by the model. PRACTICAL APPLICATIONS Olive cake is solid waste of the olive oil industry that is available in large amounts in many Mediterranean countries and at very low cost. It can be treated or valorized, enabling at the same time the solution to environmental problems caused by the olive oil production process. The economic interest that it presents is especially because of the residual oil that it contains and that can be recovered by solvent extraction. However, this solid–liquid extraction depends on several parameters: the ones inherent to the products (structure and properties of the sample, nature of extraction solvent); and the others to the extraction process (time of contact, temperature of extraction, solvent‐to‐solid ratio, stirring velocity). The experimental design method enables to determine the most important variables and their interaction in the extraction process at the same time performing a low number of experiments.

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