Journal of Chemical Thermodynamics, Vol.125, 142-148, 2018
Thermodynamics and selectivity of separation based on activity coefficients at infinite dilution of various solutes in ionic liquid [HMMIM][BF4]
The activity coefficients at infinite dilution (gamma(infinity)(i)), gas-liquid partition coefficients (K-L) of organic solutes (n-alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, chloromethanes, alcohols and 1,4-dioxane) in the ionic liquid 1-Hexyl-2,3-dimethylimidazolium tetrafluoroborate ([HMMIM][BF4])have been measured using the gas-liquid chromatographic method (GLC) at five temperatures: 313.15 K, 323.15 K, 333.15 K, 343.15 K, 353.15 K. The density of [HMMIM][BF4], as a function of temperature, was determined in atmosphere. The values of the partial molar excess enthalpies at infinite dilution ((H) over bar (E,infinity)(i)) were derived from the temperature dependence of the In gamma(infinity)(i) values. The entropies (T-ref(S) over bar (E,infinity)(i)) and Gibbs energies ((G) over bar (E,infinity)(i)) of organic solutes in [HMMIM][BF4] at a reference temperature T(r)ef = 298.15 K were calculated from the gamma(infinity)(i) values. The Hildebrand's solubility parameters of the IL [HMMIM][BF4] were determined by the regular solution theory (RST) combined with Flory ''combinatorial'' equation. Selectivity (S-ij(infinity)) and capacity (k(j)(infinity)) at infinite dilution at 323.15 K have been determined for n-hexane (i)/benzene (j), cyclohexane (i)/benzene (j). The results were analyzed in comparison to literature data for alkylimidazolium ionic liquids (ILs) with [BF4](-). The interaction between the IL and the individual solutes can be disclosed by the linear free energy relationship (LFER) analysis. (C) 2018 Elsevier Ltd.