The kinetics and thermodynamics of soybean extraction using ethanol and ethanol + alkyl esters mixtures
(biodiesel) as co-solvent were investigated. The extraction parameters investigated were temperature
(25, 40 and 55 ◦C) and biodiesel to ethanol mass ratio. The extractions were carried out in batch mode
at a fixed solvent to soybean mass ratio (4:1). Three different kinetic models were used to correlate the
overall extraction curves, namely a first-order, second-order, and a mass transfer model based on Fick’s
Law. The mass transfer model presented a mean absolute relative deviation of 4.7%, while de first and
second-order models showed values around 10.1% and 4.4%, respectively. From the experimental results
obtained, it was observed that higher temperatures affected positively the extraction yields. Furthermore,
higher mass ratio of biodiesel to anhydrous ethanol provide higher extraction yields, at temperatures of
25 and 40 ◦C. At 55 ◦C, the extraction yields were not improved when adding the biodiesel as co-solvent to
the anhydrous ethanol. On the other hand, using hydrated ethanol as solvent resulted in lower extraction
yields, so higher amounts of biodiesel were necessary to reach the same levels of extractions performed
using anhydrous ethanol. The thermodynamic analyses showed that both H◦ and S◦ are positive for
this process, while negative values ofG◦ were found, that means the process evaluated is characterized
as endothermic, irreversible and occurs spontaneously.