Comparison of liquid–liquid phase equilibrium behavior of acetonitrile–water system using choline chloride salt and water-based deep eutectic solvent

Abstract

The liquid–liquid equilibrium (LLE) data for the ternary systems of (acetonitrile (ACN) + water (W) + choline chloride (ChCl)) and (ACN + W + water-based deep eutectic solvent (WDES) consisting of ChCl:W (1:3)) were measured at 298 K. The consistency of tie-lines was verified by the Bachman and Othmer-Tobias correlations. ChCl as an organic salt and its WDES (within the water content range of less than 50 w%) as green extractants represent feasible performances in terms of selectivity and distribution coefficients for separation of water from acetonitrile-water system in comparison to other inorganic salts and hydrophobic DESs. ChCl in the (ACN + W + ChCl) system can separate water from the solution in the form of hydrate ions while WDES in the (ACN + W + WDES) system tends to absorb water by intermolecular forces. The experimental data of the (ACN + W + ChCl) system was correlated using the symmetric electrolyte non-random two liquid (e-NRTL) model while the equilibrium data of the (ACN + W + WDES) system was correlated using NRTL and universal quasi-chemical activity coefficient (UNIQUAC) models. ChCl in the form of salt represents a better separation performance than WDES for water removal from the acetonitrile mixture. Meanwhile, WDES might be considered to be superior compared to ChCl in terms of regeneration energy consumption and operating considerations.