Thermophysical Properties of Protic Ionic Liquids Monoethanolamine, Diethanolamine, and Triethanolamine Lactate in Water
Hemayat Shekaari, Mohammed Taghi Zafarani-Moattar, Saeid Faraji
Abstract
Absolute knowledge of applying protic alkanolamine ionic liquids and the comprehension of diverse thermophysical properties of these materials is necessary in different processes. In this regard, the density, speed of sound, viscosity, and refractive index data for aqueous solutions of ionic liquids (ILs), 2-hydroxyethylammonium lactate [2-HEA]La, bis(2-hydroxyethyl)ammonium lactate [2-HDEA]La, and tris(2-hydroxyethyl)ammonium lactate [2-HTEA]La were measured in dilute concentration region of ILs at T = 288.15–318.125 K under 87.1 kPa pressure. The standard partial molar volume and partial molar isentropic compressibility (Vφ0 and Κφ0) were determined from the parameters of the Redlich–Mayer equation. Also, Pitzer interaction theory was used for the correlation of the experimental values. Temperature dependence of the standard partial molar volume was applied for determining the structure making or breaking behavior of the mentioned ionic liquids in water bulk by using apparent molar isobaric expansions Eφ0 and (∂2Vφ0∂T2)p. The viscosity measurements were used to determine the viscosity B-coefficient. Finally, the solute–solvent interactions were explained with the obtained results. The results suggest that ionic liquid [2-HTEA]La has a stronger interaction with water compared to other ionic liquids.