Transport and Thermodynamic Properties of Ethylammonium Nitrate-Water Binary Mixtures: Effect of Temperature and Composition

Physical properties such as densities, rho, viscosities, eta, and conductivities, kappa, have been measured for the binary mixtures of the ionic liquid ethylammonium nitrate, EtNH3NO3, with water over the entire molar fraction range at various temperatures ranging from 293.15 to 318.15 K and under ambient pressure. Strong effects of the composition and temperature on these properties have been observed. Experimental densities and viscosities were used to calculate the corresponding excess properties. The variations of excess molar volume and excess Gibbs energy against the ionic liquid fraction show complementary extrema (minima and maxima with opposite signs). The excess molar volumes and excess viscosity deviations are well fitted using the Redlich-Kister polynomial. Moreover, the viscosity was found to be temperature dependent and followed the Arrhenius law. Variations of the activation energies for viscous flow versus the ionic liquid content revealed a modification in the medium's structure. The conductivity-temperature relationship was found to be better represented by the Vogel-Tammann-Fulcher model than with the Arrhenius equation. In addition, variations of the conductivity with composition are well described by the Casteel-Amis equation. The impact of addition of the ionic liquid to water on the viscosity and the conductivity have been also examined using Walden's rule, which shows that viscosity is highly correlated to conductivity for ionic liquid molar fractions higher than ca. 0.2. Activation thermodynamic parameters for viscous flow, calculated from the viscosity data, reveal that changes in the medium structure occur at ca. 0.2 and 0.8 molar fractions of ionic liquid.