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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RESUMENModelo matemático para la extracción de aceite de orujo usando hexano.En este artículo se estudia la influencia de los factores que pueden tener efecto en la extracción del aceite de orujo usando hexano. Se propone a partir de los resultados experimentales, un modelo matemático para el cálculo del rendimiento de la extracción. Los tests estadísticos utilizados para obtener este modelo mostraron que el rendimiento no depende de la granulometría ni de la velocidad de agitación, pero si depende de la temperatura, del tiempo de contacto y de la relación líquido-sólido (L/S). También depende de las interacciones entre el tiempo y la temperatura y entre el tiempo y la relación L/S. La comparación entre los resultados experimentales y el modelo nos permite decir que dicho modelo es satisfactorio.PALABRAS-CLAVE: Aceite de orujo -Extracción con hexano -Modelo matemático. SUMMARYModeling of oil extraction from olive foot cake using hexane.In this work, the influences of the factors, which can have effect on oil extraction from olive foot cake using hexane, are studied. From the experimental results, a mathematical model for calculation of the extraction yield is proposed. The statistical tests used to obtain this model show that the yield does not depend on the granulometry and the stirring rate, but depends on the temperature, the contact time and the liquid-solid ratio (L/S). Also, it depends on interactions between time and temperature and interactions between time and L/S. The comparison of the results given by the experiment and the model allows us to say that the model is satisfactory.KEY-WORDS: Extraction with hexane -Mathematical modelOlive foot cake.

Olive mill wastewater (OMW) is a substantial pollutant not only because of its high organic matter content and recalcitrant compounds such as polyphenols, but also due to its high chemical oxygen demand and biological oxygen demand. Its degradation by means of hydroxyl radicals generated from microwave application in the presence of hydrogen peroxide and Cu(II) has been investigated. The optimal experimental conditions were found to be a microwave intensity of 680 W, the presence of Cu(II) and relatively concentrated hydrogen peroxide (12 mol L(-1)). In these conditions, discolouration of OMW reached 98.0 +/- 0.2% and phenolic compounds decreased to 81.8 +/- 0.2% of their initial concentration after 12 min microwave time. Fourier transform infrared analysis confirmed that microwave degradation of phenols by means of the Fenton-like system Cu(II)/H2O2 could be an efficient solution for the treatment of olive mill wastewater.