Measuring and Modeling Liquid–Liquid Equilibria for a Soybean Oil, Oleic Acid, Ethanol, and Water System

Abstract

Vegetable oils can be deacidified by liquid– liquid extraction based on differences in polarity between triglycerides and fatty acids and differences in solubility. Information on the equilibrium between the phases of such systems is important for designing separation processes. The present paper reports experimental data for the extraction of fatty acid from soybean oil by (ethanol ? water) as a mixed-solvent for system of soybean oil ? oleic acid ? ethanol ? water at 30 °C at different water contents. The liquid–liquid equilibrium data of the systems were used to obtain interaction parameters in the universal quasi-chemi- cal theory (UNIQUAC) activity coefficient model. These parameters can be used to predict equilibrium data of ternary and quaternary systems. The deviations between experi- mental and calculated compositions in both phases for each system using this model were calculated. The distribution coefficients and the selectivity factors of solvents for extraction of fatty acid from oil at 30 °C were calculated. Increasing of the water content as the co-solvent decreased the distribution coefficients and increased the selectivity factors of mixed-solvents, therefore considering the eco- nomical and practical aspects the optimum water content may be used for extracting oleic acid from soybean oil. We concluded that (ethanol ? water) as a mixed-solvent can be used for extracting fatty acids from edible oils in a normal temperature.