Application of the SAFT-VR equation of state in calculation of osmotic coefficient of aqueous solutions of ionic liquids

In this work, an equation of state based on the statistical associating fluid theory for potentials of variable range (SAFT-VR) was used to calculate the osmotic coefficient of dilute aqueous solutions of ionic liquids including 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and 1-butyl-3-methylimidazolium methylsulfate ([bmim][MS]). In order to get a clear picture of interactions among different species the follows interactions were taken in to account. The solvent–solvent hydrogen bonding interactions were explicitly elucidated using different versions of the SAFT equation of state. In addition, the long-range coulombic interactions between ionic species were accounted using the non-restricted mean-spherical approximation, while solvent–solvent and solvent–ion dispersion interactions were evaluated using the Yukawa potential in the SAFT-VR framework. Also, a similar approach was used in which the dispersion interactions were modeled using the square-well potential. The results obtained were compared and it was shown that the Yukawa potential in the SAFT-VR framework provide slightly better agreement with the experimental data for the osmotic coefficient.

Keywords:

SAFT-VR , Ionic liquid , Yukawa intermolecular potential , Square-well intermolecular potential