Excess Thermodynamic Properties for Binary Mixtures of Ionic Liquid 1-Ethyl-3-methylimidazolium Ethyl Sulfate and 2-Methoxyethanol from T = (298.15 to 328.15) K at Atmospheric Pressure

Abstract

The density (ρ), speed of sound (u) and refractive index (n D) for pure [Emim][EtSO4], 2-methoxyethanol and their binary mixtures were measured using an Anton Paar vibrating tube density and sound velocity meter (DSA 5000 M) and automatic refractometer over the whole composition range as a function of temperature between 298.15 and 328.15 K in steps of 10 K at atmospheric pressure. Experimental values were used to calculate the excess values of molar volumes (\( V_{\text{m}}^{\text{E}} \)), partial molar volumes (\( \overline{V}_{\text{m}}^{\text{E}} \)), partial molar volumes at infinite dilution (\( \overline{V}_{\text{m}}^{{{\text{E,}}\infty }} \)), isentropic compressibility (\( \kappa_{S}^{\text{E}} \)), acoustic impedance (Z E), free length (\( L_{\text{f}}^{\text{E}} \)), speeds of sound (\( u_{{}}^{\text{E}} \)), internal pressure (\( \mathop \pi \nolimits_{i}^{\text{E}} \)), free volume (\( V_{\text{f}}^{\text{E}} \)) and deviations in refractive index ( \( \Delta_{\phi } n_{\text{D}} \)) for the binary mixtures. These properties were fitted to a Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. The negative values of \( V_{\text{m}}^{\text{E}} \), \( \kappa_{S}^{\text{E}} \), \( L_{\text{f}}^{\text{E}} \),\( \alpha_{p}^{\text{E}} \), and \( V_{\text{f}}^{\text{E}} \) and positive values for Z E, \( u_{{}}^{\text{E}} \),\( \mathop \pi \nolimits_{i}^{\text{E}} \), and \( \Delta_{\phi } n_{\text{D}} \) indicate the existence of strong interactions between the components. This was further supported by IR spectroscopy analysis.