No abstract

A deep understanding of the solute‐ deep eutectic solvent (DESs) interactions is required for an appropriate selection of DESs as absorption media in the extraction of binary mixtures. As a result, these studies are done to evaluate the values of the activity coefficients at infinite dilution ( ), allowing us to define and understand the nature of these intermolecular interactions comprising DES mixtures with volatile organic solvents at different temperatures using gas liquid chromatography technique to determine the for 34 solutes in DESs [zinc chloride+acetic or phosphoric acid] prepared at 1 : 2 molar ratio for the temperature range (313.15–353.15) K. The thermal stability of the prepared DESs was determined by a thermogravimetric analyser. Excess thermodynamic parameters [partial molar excess enthalpies and Gibbs free energies ] were derived from the data. The selectivity and capacity values for the industrial separations were calculated and compared with the literature values of other DESs, ionic liquids, and sulfolane to assess the suitability of the investigated DESs for possible applications as extracting solvents. The selectivity and capacity values are high and therefore, [zinc chloride+acetic or phosphoric acid] can be used as a potential solvent to replace the currently used conventional solvents in the separation of the selected azeotropes. COSMO‐SAC predictions were qualitatively in very good agreement with the experimental data.

In this study the experimental density, speed of sound, and refractive index for binary mixtures of an ionic liquid (IL): 1-butyl-3-methylimidazolium nitrate and activity coefficients at infinite dilution of organic solutes in the ionic liquid: 1-butyl-3-methylimidazolium hydrogen sulfate were determined. The density, speed of sound, and refractive index of 1-butyl-3-methylimidazolium nitrate in pyridine or acetonitrile or thiophene have been reported at T = 298.15 K, 303.15 K, 308.15 K, 313.15 K and 318.15 K using an Anton Paar DSA 5000M vibrating U-tube densimeter and a RXA 156 refractometer. The derived properties namely: excess molar volume, isentropic compressibility and change in refractive index were calculated from density, speed of sound and refractive index, respectively. The results are discussed in terms of molecular interactions (hydrogen bond, dipole-dipole, or ion-solvent or interactions). The negative deviation of excess molar volume and the positive deviation in change in refractive index clearly indicates the strong interaction of 1-butyl-3-methylimidazolium nitrate with pyridine or acetonitrile or thiophene in solution. The positive values of isentropic compressibility for the system indicates that the mixtures were more compressible than the ideal mixture. The Redlich Kister smoothing polynomial was used to fit the excess molar volume and deviation in isentropic compressibility data. The Lorentz-Lorenz equation was used to predict the experimental density, or refractive index data and to correlate the excess molar volume. Gas liquid chromatography was used to determine activity coefficients at infinite dilution for 28 polar and non-polar organic solute: alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, aldehydes, thiophene, pyridine and acetonitrile in an IL: 1-butyl-3- methylimidazolium hydrogen sulfate ([BMIM][HSO4]). The measured values of activity coefficients at infinite dilution for the solutes in [BMIM][HSO4] were carried out at T = (313.15, 323.15, 333.15) K. Partial molar excess enthalpies at infinite dilution of the organic solutes in the ionic liquid have been calculated from the temperature dependence of activity coefficients at infinite dilution. The selectivity and capacity values for separation problems namely: hexane/benzene, heptane/benzene, cyclohexane/benzene, ethanol/benzene, heptane/pyridine, heptane/thiophene and methanol/acetone at T = 323.15 K were calculated and compared to literature values for similar ionic liquids, sulfolane and N-methyl-2- pyrolidinone (NMP). The IL [BMIM][HSO4] gave both the highest selectivity and limiting capacity for the heptane/thiophene separation and would therefore be a suitable entrainer for this separation. New data from this study reveals that [BMIM][HSO4] may be proposed as a replacement solvent for the separation of sulphur or nitrogen compounds from alkanes.