Properties of n-butylpyridinium nitrate ionic liquid and its binary mixtures with water

The density and surface tension of the pure ionic liquid n-butylpyridinium nitrate ([BuPy]NO3) were determined at temperature range from T = (293.15 to 338.15) K. The coefficient of thermal expansion, molecular volume and lattice energy of [BuPy]NO3 were calculated from the experimental values of density. The surface entropy and enthalpy of [BuPy]NO3 were investigated. The IL studied show much lower surface enthalpy and lattice energy in comparison with fused salts. The densities and surface tensions of binary mixtures of [BuPy]NO3 with water have been measured within the whole composition range at T = 298.15 K and atmospheric pressure. Excess molar volumes VE and surface tension deviations δγ were then deduced from the experimental results as well as partial molar volumes and excess partial molar volumes. Excess molar volumes have a negative deviation from ideal behavior and the surface tension deviations are negative over the whole compositions range. VE and δγ were correlated with suitable equation respectively.

► Density and surface tension of [BuPy]NO3 have been measured.
► Thermal expansion coefficient, molecular volume and lattice energy were obtained.
► The surface properties, critical temperature were discussed.
► Density and surface tension were measured for ([BuPy]NO3 + water) mixtures.
► Excess molar volumes and surface tension deviations were fitted to an equation.