Water sorption by anhydrous ionic liquids

Francesco, Fabio Di; Calisi, Nicola; Creatini, Matteo; Melai, Bernardo; Salvo, Pietro; Chiappe, Cinzia

doi:10.1039/c1gc15080d

Cited by 111 publications

(159 citation statements)

References 30 publications

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“…Their study also took a long time for the ILs to either reach or begin to approach equilibrium with exposed water vapor; anywhere from 20 to 60+ h at 43% RH. 12 4 ] took the longest time to reach equilibrium and absorbed the most amount of water, concluding that it was the most hydrophilic of the ILs in their study. 12 The kinetic limitations associated with large quantities of IL in previous studies of water vapor absorption by imidazolium-based ILs can be circumvented by studying water uptake by IL nanoparticles (a few tens of nanometers in diameter) or thin films (a few micrometers in thickness).…”

Section: ■ Introductionmentioning

confidence: 97%

“…12,34 Previous studies were performed on bulk quantities of ILs. However, there are kinetic limitations associated with studying large quantities of ILs, often taking several hours or longer for bulk ILs to reach equilibrium with water vapor.…”

Section: ■ Introductionmentioning

confidence: 99%

“…34 In a similar study, Di Francesco et al examined the kinetics of water vapor uptake by several ILs at two RH levels, 43% and 81% RH, using gravimetric analysis on initial ILs volumes of 2 mL. 12 The results showed that the more hydrophilic ILs absorbed more water vapor compared to the more hydrophobic ILs. Their study also took a long time for the ILs to either reach or begin to approach equilibrium with exposed water vapor; anywhere from 20 to 60+ h at 43% RH.…”

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

et al. 2012

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Understanding the interactions of humid air with ionic liquids (ILs) is critical for predicting how their physicochemical properties are affected by water. Using experimental and theoretical techniques, water vapor's interaction with aerosolized nanoparticles and thin films of [C 2 MIM][Cl] and [C 2 MIM][BF 4 ] was studied. Solutions were electrosprayed to produce dry particles. Particles' hygroscopic growth was quantified using tandem nanodifferential mobility analysis as a function of relative humidity (RH). This is the first report of the interaction of water with aerosolized IL nanoparticles. The particles' small size allows true IL−water vapor equilibrium achieved quickly. Growth curves for both ILs show steady water uptake with increasing RH. Water vapor uptake by IL thin films was also examined using ATR-FTIR spectroscopy. . They represent a large class of molecules that have unique and widely tunable physical and chemical properties. 1−3 For example, there is a significant interest in the use of ILs in green chemistry, 2,4,5 due to their negligible vapor pressure at room temperature, 6 and for many other applications including solvents in synthesis and catalysis, 1,6 chemical extraction, 1,2,5 and fuel cells. 7 Physical properties such as conductivity, viscosity, density, and surface tension of ILs are known to depend on the presence of water, both adsorbed and absorbed. 3,8 Water is ubiquitous in the environment, and hygroscopic ILs such as those with imidazolium-based cations can uptake significant amounts of water vapor from ambient air, which alters their physical and chemical properties. 1,3 Thus, quantification of water uptake by hygroscopic ILs and understanding how the presence of water affects the nature of the ion−ion and ion−water interactions are critical for use of ILs in future applications. 8−14 Numerous experimental and theoretical studies have investigated the interaction of imidazolium-based ILs with water. 3,8−35 It is understood that both the cation and the anion have an effect on how ILs interact with water, with the anion having a stronger effect. 3,17,19 Early experimental work by Seddon et al. investigated the miscibility of water with ILs containing 1-nalkyl-3-methylimidazolium ([C n MIM + ], n = number of carbons on the linear alkyl chain) cations and various anions at room temperature. 3 It was determined that, regardless of the alkyl chain length, all halide anions were fully soluble in water and all hexafluorophosphate ([PF 6 − ]) anions were insoluble. 3 However, alkyl chain length did have an effect on water miscibility of [C n MIM + ]-based ILs with tetrafluoroborate ([BF 4 − ]) anions; for chain lengths of n = 2 or 4, the ILs were fully miscible, but for n > 4, the ILs formed biphasic systems. 3 Cammarata et al. performed early attenuated total reflection (ATR) infrared (IR) studies on the molecular states of water

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Section: ■ Introductionmentioning

confidence: 97%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

et al. 2012

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“…On the other hand, the information on the hygroscopicity of ILs is fundamentally important in understanding the structure/hygroscopicity relationship of ILs because the hygroscopicity of ILs has been reported to closely associate with the composition of ILs [24]. For instance, ILs with anions such as halides, nitrate, methyl sulfonate or formate normally have a good water miscibility, whereas ILs with anions such as hexafluorophosphate or bis(trifluoromethylsulfonyl)imide may have poor water miscibility [25]. Similarly, the anions of ILs may have a large effect on the water miscibility of ILs [25,26].…”

Section: Introductionmentioning

confidence: 98%

Electrochemical Quantification of Hygroscopicity of Ionic Liquids with Solution‐Dissolved Potassium Ferricyanide as the Redox Probe

Qian

Cheng

et al. 2011

Electroanalysis

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Quantification of hygroscopicity of ionic liquids (ILs) is of great importance in both fundamental studies and practical applications of ILs. This study demonstrates an electrochemical method for effectively quantifying the hygroscopicity of ILs through electrochemically monitoring water contents absorbed into ILs. The measurements of water content absorbed into the ILs are performed with square wave voltammetry (SWV) based on the water-induced enhancement of diffusion of solution-dissolved potassium ferricyanide (K 3 Fe(CN) 6 ) redox probe. For demonstration, two kinds of ILs with different hygroscopicity (i.e., hydrophilic Bmim + Gly À and hydrophobic Bmim + PF 6 À ) are employed in this study. The dissolution of K 3 Fe(CN) 6 redox probe into ILs is found to have little effect on the hygroscopicity of ILs. The hygroscopicity of ILs is thus able to be quantified by monitoring water content absorbed into ILs as a function of time when ILs are stored at room temperature and standard atmospheric pressure under 55 % relative humidity (RH). Under the conditions employed in this study, the hygroscopicity of Bmim + Gly À and Bmim + PF 6 À is determined to be 1.33 M per hour and 0.05 M per hour, respectively, which are almost consistent with those measured with Karl Fischer titration under the same conditions. The electrochemical method demonstrated in this study is experimentally simply and environmentally benign and may be potentially extended for general quantification of hygroscopicity of ILs.

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“…They are characterized by outstanding physical as well as chemical properties of very low vapor pressure, wide range of solubility, good chemical and thermal stability compared to common organic solvents [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Improved Methodology for Absorption Measurements in Ionic Liquids with a Quartz Crystal Microbalance

Schmidt

Heym

2017

Chem Eng & Technol

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The knowledge of vapor‐liquid equilibrium data of mixtures with performance chemicals, such as ionic liquids (ILs), is highly important for technical applications. New insights into the utilization of quartz crystal microbalances (QCMs) for reliable absorption measurements in ILs are provided. The validity of the Sauerbrey equation for rigid films and bulk liquids is widely discussed in literature. This work shows how to ensure the validity of the Sauerbrey equation during absorption measurements in thin liquid films. Furthermore, the advantages of the employment of rough electrodes for absorption measurements within thin liquid films in comparison to polished ones are described in detail. Important recommendations in application of the QCM systems regarding gravimetric measurements are presented.

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Water sorption by anhydrous ionic liquids

Cited by 111 publications

References 30 publications

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

Electrochemical Quantification of Hygroscopicity of Ionic Liquids with Solution‐Dissolved Potassium Ferricyanide as the Redox Probe

Improved Methodology for Absorption Measurements in Ionic Liquids with a Quartz Crystal Microbalance

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