Studies of Volumetric and Transport Properties of Ionic Liquid–Water Mixtures and Its Viability To Be Used in Absorption Systems

Abstract

Binary systems of two ionic liquids (ILs), 1-ethylpyridinium methanesulfonate [C2Py]­[MeSO3] and choline dihydrogen phosphate [Chol]­[H2PO4], and water have been experimentally studied. Density, viscosity, electrical conductivity and proton activity have been measured at several temperatures covering all the miscibility range. From density data, isobaric coefficient of thermal expansion was calculated to study the volumetric behavior of the mixtures. All volumetric data were fit using polynomial equations. The Vogel–Fulcher–Tamman (VFT) equation accurately describes the temperature dependence of viscosity for all systems. Systems based on [C2Py]­[MeSO3] are less dense and viscous than those involving [Chol]­[H2PO4], making [C2Py]­[MeSO3] more suitable for absorption systems where pumping cost has a significant importance. Electrical conductivity data were adjusted using the Casteel–Amis equation. Similar trends were found for both systems, although ionic conductivity is higher for [C2Py]­[MeSO3] + H2O mixtures. The relation between viscosity and electrical conductivity was also explored. According to Walden plots, ILs present low ionicity; however, internal friction and ionic concentration does not seem to be enough to explain the behavior of ionic conductivity and IL concentration. Proton activity measurements show different tendencies with molar fraction of each IL, [C2Py]­[MeSO3] leads to lower pa H+ values than [Chol]­[H2PO4] in the binary mixtures. Results of ionic conductivity and proton activity suggest a higher corrosive potential of [C2Py]­[MeSO3] + H2O; however, a further analysis needs to be done to evaluate this risk in absorption systems. Finally, a composition analysis based on ionic chromatography (IC) was carried out to obtain insight about its effect on their physicochemical properties.

Structure, Molecular Interactions, and Dynamics of Aqueous [BMIM][BF4] Mixtures: A Molecular Dynamics Study

“…It is partly because many ILs are hygroscopic and absorb water from the environment. In addition, water is known to alter the properties of ILs including viscosity, polarity, structure, and ionic conductivity. − The application of ILs can be expanded by mixing with water or other solvents . Many computational studies have been undertaken to investigate IL–water mixtures.…”

Ecotoxicity of binary mixtures of ILs and inorganic salts of electrochemical interest

“…Aside from non-volatility, other characteristic properties of ILs include high thermal and chemical stability, high viscosity, solubility in water and other solvents, a wide electrochemical window and especially tuneability (Yasuda et al 2013). All these characteristics make ILs good candidates to be used in high-temperature applications such as lubrication (Otero et al 2014), desulfurization of fuels (Gutiérrez et al 2018), batteries (Menne et al 2013;Balducci 2017;Wang et al 2020), fuel cells (Nakamoto and Watanabe 2007), fluids in refrigeration systems (Sánchez et al 2016;Moreno et al 2018) and APIs (Shamshina and Rogers 2020).…”

Molecular Dynamics Insights into the Nanoscale Structural Organization and Local Interaction of Aqueous Solutions of Ionic Liquid 1-Butyl-3-methylimidazolium Nitrate

“…Economical utilization of aqueous solutions of ILs (versus the neat ILs) can help to overcome the cost challenge associated with commercialization of IL-related technologies . Furthermore, the addition of water reduces the (high) viscosity of ILs which is necessary to implement ILs efficiently at industrial scale, especially for low temperature applications such as utilization of the IL–water mixture in the absorption heat pumps and absorption chillers . IL–water mixtures are promising separation media for bioactive compounds .…”