Water Sorption in Functionalized Ionic Liquids: Kinetics and Intermolecular Interactions

The water sorption by nine functionalized imidazolium based ionic liquids (ILs) with the effects of temperature and relative humidity were investigated. Three kinds of parameters (sorption capacity, sorption rate, and sorption equilibrium) were derived to comprehensively characterize the sorption processes. A sorption triangle was proposed to correlate these kinds of parameters, which were the corresponding three vertices of this triangle. The sorption triangle has three effective categories numbered types 1, 2, and 3. The hydrophilicity of the ILs was sorted into four levels according to the steady-state water sorption capacity. The sorption results were consistent with the water–IL interaction investigation with attenuated total refletance infrared (ATR-IR) and nuclear magnetic resonance (NMR) spectra. The functionalized ILs investigated in this study are more hydrophilic than conventional ILs from a statistical view.