Modelling thermophysical properties of mixtures of 2-hydroxyethyl ammonium-based ionic liquids + water, methanol, or ethanol with the electrolyte-cubic plus association equation of state

This work presents a theoretical study using the electrolyte Cubic-Plus-Association (e-CPA) equation of state combined with quantum chemistry computations, for modeling the density and speed of sound of mixtures containing 2-hydroxyethylammonium-based (2-HEA-based) ionic liquids (ILs) + water/methanol/ethanol over wide ranges of temperatures. The e-CPA ion parameters were estimated by a simultaneous fitting of densities and speed of sounds of pure ILs. Aiming to reduce the number of adjustable parameters, the ion parameters were obtained by COSMO (Conductor-like Screening Model) volume implemented in MOPAC2016 (Molecular Orbital PACkage) based on the geometry optimization of ion structures. The results show that the e-CPA can satisfactorily predict the density and speed of sound of 2-HEA-based ILs + solvents with an absolute average deviation lower than 3%. The addition of two extra binary interaction parameters (solvent-cation and solvent-anion) can further reduce the overall deviation by less than 1%. The sensitivity analysis revealed that only the speed of sound of the 2-HEA-based ILs + solvent mixture is affected by changes in ion radii and dipole moment.