Study of Thermodynamic and Transport Properties of the Ternary System (1-Hexyl-3-Methylimidazolium Bromide + Ethanol + Water) Based on Potentiometric and Conductometric Measurements

In this work, the molar conductivities and mean activity coefficients of 1-hexyl-3- methylimidazolium bromide [HMIm]Br in the ternary system [HMIm]Br + ethanol + water were reported using conductometric and potentiometric techniques, respectively. Conductometric data wereobtained for [HMIm]Br ionic liquids from 0.0008 to 0.2496 mol·kg^–1 on various mass fractions of ethanol in ethanol + water mixtures ((w/w)% = w_ethanol/w_mixture = 0, 10, 20, and 30%) at T = 298.2, 308.2, and 318.2 K. Ion association constants (K_a) and limiting molar conductivities (Λ₀) of [HMIm]Br were achieved by the Fuoss–Onsager equation and utilized to get the thermodynamic functions. Moreover, potentiometric data were collected for the galvanic cell of the type: [HMIm]–ISE|[HMIm]Br(m_[HMIm]Br), ethanol (wt)%, H₂O (1 -wt) %|Br–ISE in water + ethanol mixtures (w_ethanol /w_{water+ethanol} = 0, 10, and 20%) over the ionic strength varying from 0.0094 to 1.7437 mol·kg^–1 at T = 298.2 and 308.2 K. Thermodynamic properties modeling was implemented using the Pitzer ion interaction model and the values of Pitzer ion-interaction parameters β⁽⁰⁾, β⁽¹⁾, and C^φ were evaluated. Then, thermodynamic properties, such as mean activity coefficients, excess Gibbs free energy, osmotic coefficients, and solvent activity. were determined.