Activity Coefficients at Infinite Dilution of Various Solutes in Tetrapropylammonium Bromide + 1,6-Hexanediol Deep Eutectic Solvent

The present work focuses on the application of a deep eutectic solvent (DES) to the separation of liquid mixtures. Experimental activity coefficients at infinite dilution γ13∞ of 23 organic solutes in tetrapropylammonium bromide +1,6-hexanediol DES were measured by gas–liquid chromatography (GLC) at four temperatures ranging from (313.15 to 343.15) K and atmospheric pressure. The hydrogen bond acceptor-to-hydrogen bond donour molar ratio was 1:2. The effect of molecular structure on the values of γ13∞ was also examined. From experimental limiting activity coefficients, values of partial molar excess enthalpy at infinite dilution (ΔHiE,∞) were obtained using the Gibbs–Helmholtz equation over the same temperature range. Furthermore, infinite dilution selectivity (Sij,s∞) and capacity (kj,s∞) for various practical separation problems were calculated from experimental γ13∞ and were compared with those of previously investigated ionic liquids and popular industrial solvents. It was observed that the investigat...