Separation of ethanol azeotropic mixture using deep eutectic solvents in liquid- liquid extraction process

Abstract In the current study three deep eutectic solvents (DES) including (Malonic acid (1:1) Choline chloride), (Malic acid (1:1) Choline chloride) and (Malic acid, Malonic acid (1:1:1) Choline chloride) were prepared and used for separation of ethanol- hexane azeotropic mixture for the first time. 1H NMR analysis of the solvents confirmed the construction of the DESs. The liquid–liquid equilibrium data of pertinent ternary systems were obtained at 298.15 and 308.15 K and atmospheric pressure. Comparison of the distribution coefficient and selectivity of ethanol at different feed compositions for each tie- line, with the result of the literature revealed that the prepared DESs were more efficient than using ionic liquids and DESs by previous investigators. Both values of distribution coefficient and selectivity were far larger than unity at all concentration ranges. The (Malonic acid (1:1) Choline chloride) DES showed the highest values of selectivity over than 11,000 at low concertation range of ethanol, while the distribution coefficient of ethanol exceeded 45 for the same mixture. Also, the effect of DES concentration in the feed was assessed at two temperatures and atmospheric pressure. Moreover, a non-random two liquid (NRTL) model of excess Gibbs energy was used to correlate the equilibrium composition of the extraction by the DESs. The RMSD value of the model for all studied systems was lower than 0.035, which presented the capability of the NRTL model for the prediction of LLE in ternary systems of ethanol- hexane- DESs.