Solvent pre-selection for binary mixtures based on the activity coefficient at infinite dilution in deep eutectic solvent: Tetraethylammonium chloride+ Ethylene glycol

The values of activity coefficient at infinite dilution ( γ 12 ∞ ) were reported for 27 solutes in tetraethylammonium chloride + ethylene glycol deep eutectic solvent (DES) system at a molar ratio of 1.000:1.997 by inverse gas chromatography (IGC) method at intervals of 10 K from 303.15 to 333.15 K. Then the measured γ 12 ∞ values were used to determine the thermodynamic functions ( Δ H 1 E , ∞ , Δ S 1 E , ∞ , and Δ G 1 E , ∞ ). The values of selectivity ( S i j ∞ ) and capacity ( k j ∞ ) for six extraction problems (that is, heptane/toluene, benzene/methanol, heptane/thiophene, acetone/ethanol, cyclohexane/benzene, and cyclohexane/ethanol.) were calculated from experimental γ 12 ∞ values and compared with literature values of other solvents under the same separation conditions. The results indicate that the studied DES is a potential extractant for separation of cyclohexane/ethanol and heptane/thiophene systems. The Flory-Huggins interaction parameters ( χ 12 ∞ ) were used to evaluate the miscibility between DES and organic probes, and the results reveal that alcohols exhibited the best solubility in tested DES. Furthermore, the Hildebrand solubility parameters ( δ 2 ) were calculated for tested DES, and the values of δ 2 decreased with the increase of temperature.