The Interaction Exploration of the Dilute Solutions of [EtOHEIm][SCN] with Organic Solvents: Apparent Molar Volume and Molar Surface Gibbs Energy

In this paper, the density and surface tension measurements of both dilute solutions of [EtOHEIm][SCN] in acetonitrile and ethanol were measured at T = (293.15–318.15) K and m = (0.0300–0.3000) mol·kg –1 . The apparent molar volume, V Φ, and the infinite dilution apparent molar volume, V Φ ∞, obtained via the Redlich–Mayer equation were employed to analyze solute–solvent interactions, particularly hydrogen bonding. The limiting apparent molar expansivity values, E Φ ∞, were evaluated by the temperature dependence of V Φ . In addition, the positive surface tension deviations (Δγ > 0) in both acetonitrile and ethanol systems indicate stronger solute–solvent interactions between [EtOHEIm][SCN] and the solvents. The molar surface Gibbs energies were worked out, and the relationship between the molar surface Gibbs energy and molality was explored; moreover, the corresponding entropy and enthalpy were determined using the improved Eütvüs equation. These results have been explained from the point of view solute–solvent interactions. More importantly, it was concluded that primary interactions between [EtOHEIm][SCN] and solvents are hydrogen bonds, and the interaction force is strongest in the acetonitrile system.