Measurements of activity coefficient at infinite dilution for organic solutes in tetramethylammonium chloride + ethylene glycol deep eutectic solvent using gas-liquid chromatography

Deep eutectic solvents (DESs) are considered as the new ionic liquids (ILs) analogues that have emerged as potential alternative 'green' solvents, for a diversity of applications. In this study, a type III DES based on ammonium salt was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Activity coefficients at infinite dilution, γ13∞ for 19 organic solutes in the tetramethylammonium chloride + ethylene glycol DES were measured by the gas-liquid chromatography (GLC) method at four temperatures in the range from (313.15-343.15) K. Experimental measurements were undertaken with an overall uncertainty of ±5.4%. The effect of the structure of the solutes on γ13∞ was also investigated. For all investigated solutes, Gibbs helmholtz relationship was utilised to derive partial molar excess enthalpy values at infinite dilution (ΔHiE,(∞)) from experimental limiting activity coefficient data. From selectivity (Sij∞) and capacity (kj∞) values at infinte dilution, it was concluded that the investigated DES has the potential to replace a number of industrial solvents for the separation of various industrial mixtures.