Effect of Relative Humidity of Air on Density, Apparent Molar Volume, Viscosity, Surface Tension, and Water Content of 1-Ethyl-3-methylimidazolium Ethylsulfate Ionic Liquid

Abstract

The effect of relative humidity (RH) of air on the water content, density, apparent molar volume, dynamic viscosity, and surface tension of the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate has been studied. Physical property measurements were conducted at a temperature of 298.15 K, at atmospheric pressure, and in a RH range of (0 to 100) %. The experimental data were fit to first- and third-order polynomials that relate the physical properties with the relative humidity of air and the water content of [emim][EtSO4] with correlation coefficients higher than 0.9. The apparent molar volume was fit by the Redlich−Mayer equation with a relative standard deviation (σ) less than 2 cm3·mol−1. Excess molar volumes, viscosity, and surface tension deviations of a mole fraction average were calculated, and a second- and third-order Redlich–Kister polynomial was applied (σ equal to 0.01 cm3·mol−1, 0.5 mPa·s, and 0.6 mN·m−1, respectively).