Evaluation of an imidazolium-based ionic liquid as a separation solvent for binary mixtures based on limiting activity coefficient data

Abstract

The separation of volatile organic solvents (herewith, solutes) were tested in an imidazolium-based ionic liquid (1,3-dimethylimidazolium dimethylphosphate), [MMIM] [DMP] as a solvent at four different temperatures, T = (313 .15 to 343.15) K and at atmospheric pressure. The solutes include alcohols, aromatic hydrocarbons, thiophene, ketones, alkanes, alkynes, alkenes, acetonitrile, THF, as well as water. The separation potential of the investigated ionic liquid was based on the activity coefficients at infinite dilution, γ13∞, of organic solutes. This was based on the retention data acquired by gas liquid chromatography. Excess thermodynamic parameters at infinite dilution such as Gibbs free energy, ΔG1E,∞, entropy term, TrefΔS1E,∞ and partial molar enthalpy, ΔH1E,∞ were determined from the γ13∞ data. The results are discussed in terms of intermolecular interactions occurring between the solutes under investigation and the ionic liquid. The effectiveness of 1,3-dimethylimidazolium dimethylphosphate to separate some of the separation problems discussed in this work is determined from the selectivity and capacity values calculated from the limiting activity coefficients at infinite dilution. These thermodynamic functions can be used to develop, design or optimise industrial extraction processes.