Measurements of thermodynamic properties and activity coefficients at infinite dilution of selected organic solutes and water in a deep eutectic solvent (choline chloride +1,3 propanediol)

Abstract

In this study, a deep eutectic solvent (DES) consisting of choline chloride (ChCl) and 1,3 propanediol (Pdiol) at a 1:2 M ratio was evaluated experimentally for its extractive efficiency. The important DES’s physicochemical properties: density, viscosity, and refractive index, were measured at T = (293.15–353.15) K and 101.3 kPa. Solvent intermolecular interaction strengths against 32 selected organic solutes were assessed using experimental infinite dilution activity coefficients (IDAC) measured at T = (313.15 to 343.15) K and 101.3 kPa. The interactions between the solute and solvent molecules were further characterised by partial molar excess properties (ΔH E,∞ i pacity (k ∞ , ΔG ∞ j E,∞ i and T ref ΔS E,∞ i ). The separation ability of the solvent was assessed using selectivity (S ij ) and ca) as thermodynamic separation parameters. DES indicated stronger interactions with more polar molecules. The findings indicate that DES is suitable for separating the alkanes from alcohols, acetonitrile or thiophene mixtures. This work adds to the DES database and offers a theoretical framework for industrial separation problems.