Solution Thermodynamics of Imidazolium-Based Ionic Liquids and Water (original) (raw)
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Analytical and Bioanalytical Chemistry, 2005
Owing to their favorable properties, ionic liquids have recently gained recognition as possibly environmentally benign solvents. Now among the most promising industrial chemicals, they have already been labeled ''green'', but this appellation seems due entirely to their very low vapor pressure. This growing interest in the various applications of ionic liquids will soon result in their presence in the environment. Therefore, reliable analytical tools for the environmental analysis of ionic liquids need to be developed urgently. This paper presents a newly developed analytical procedure for the enrichment of 1-alkyl-and 1-aryl-3-methylimidazolium ionic liquids from water samples. The method is based on cation exchange solid-phase extraction followed by selective elution. Pre-concentrated samples are subjected to high-performance liquid chromatography (HPLC) with an advanced methodology for qualitative and quantitative analysis. The overall procedure was verified by using standard spiked samples of tap water, seawater, and freshwater.
Temperature effect on adsorption of imidazolium-based ionic liquids at liquid–liquid interface
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
The synthesized imidazolium-based ILs act as cationic surface active agent at the interface. Surface active properties of the used ILs enhance with their alkyl chain length. The CMC of each IL shows a minimum value at around 303 K. The experimental data fit quite well with the Frumkin adsorption isotherm. Adsorption tendency, effectiveness and interaction exhibit specific variations with temperature.
Adsorption of ionic liquids from aqueous effluents by activated carbon
Carbon, 2009
The separation of imidazolium-based ionic liquids (ILs) from aqueous solution by adsorption has been investigated using a commercial activated carbon (AC) as adsorbent. Equilibrium experiments were carried out for obtaining the adsorption isotherms of ILs on AC at different temperatures. The influence of both cation and anion was analyzed by studying 17 different ILs. The role of the surface chemistry of the adsorbent was also examined using ACs modified by oxidative and thermal treatments. The incorporation of IL on the AC surface was studied by N 2 adsorption-desorption measurements and elemental analysis. In addition to this, a COSMO-RS computational approach was developed to estimate molecular and thermodynamic properties of the solvent-adsorbate-adsorbent system, which allowed us to analyze the adsorption mechanism from a molecular point of view. The results of this work indicate that the adsorption with AC is an affordable environmental application to remove hydrophobic ILs from water streams, proposing the use of acetone for adsorbent regeneration. It has also been demonstrated that the adsorption of refractory hydrophilic ILs can be improved by modifying the amount and nature of oxygen groups on the AC surface, particularly by including hydroxyl groups to promote hydrogen-bonding interactions with the basic groups of hydrophilic ILs.
Interaction of imidazolium type ionic liquids with the solid phase
Some ionic liquids (ILs) are structurally analogous to surfactants, especially those, which contains long alkyl chain organic cations. Characteristic composition of alkylimidazolium ILs indicates that solid phase surface behavior could influence the properties of the systems containing these compounds. Ability to self associate could influence on process and effectiveness of mass transfer in many unit operations and processes, for example extraction, nanofiltration and catalytic reactions. The aggregate formation will also have significant influence on the environmental distribution, and chemical fate of these chemical entities. Understanding the molecular interactions of ionic liquids in aqueous solution is a prerequisite for sustainably predicting the environmental fate of these neoteric chemicals, which include the interaction of the ionic liquids with porous media. It will dictate transport parameters and chemical fate assessment. Therefore the determination of these solid phase...
An overview of the mutual solubilities of water–imidazolium-based ionic liquids systems
Fluid Phase Equilibria, 2007
Ionic liquids (ILs) are a novel class of chemical compounds with interesting properties that are driving a lot of research in several fields. For ionic liquids to be effectively used as solvents in liquid-liquid extractions, the knowledge of the mutual solubilities between ILs and the second liquid phase is fundamental. Furthermore, while ILs cannot volatilise and lead to air pollution, even the most hydrophobic ones present some miscibility with water posturing secondary aquatic environmental risks. Despite the importance of the ILs and water systems, there are few extensive reports on their phase equilibria. The aim of this work is to discuss and understand the mutual solubilities of water and imidazolium-based ILs. The results indicate that these mutual solubilities are primarily defined by the anion followed by the cation alkyl side chain length. It was also found that the solubility of the studied ILs in water is more dependent on the ILs structural modifications than the solubility of water in those ILs. The substitution of the most acidic hydrogen in the imidazolium cation by a methyl group leads to different behaviours in both rich-phases, where the solubility of water in ILs showed to be more hydrogen bonding dependent. From the solubility results it can be concluded that the hydrophobicity of the anions increases in the order [BF 4 ] − < [CH 3 (C 2 H 4 O) 2 SO 4 ] − < [C(CN) 3 ] − < [PF 6 ] − < [N(SO 2 CF 3 ) 2 ] − while the hydrophobicity of the cations increases, as expected, with the alkyl chain length increase.
Journal of Applied Solution Chemistry and Modeling, 2014
Imidazolium-based chloride ionic liquids (ILs) have exhibited remarkable performance in several important applications such as biomass dissolution and extraction, but their large viscosity is a non-negligible problem. Adding molecular co-solvents into chloride ILs is effective in reducing viscosity; nevertheless, understanding of the accompanied change of thermodynamic polarity is quite few. Therefore, in this work we reported three Kamlet-Taft solvatochromic parameters, including dipolarity/polarizability (*), hydrogen-bond acidity () and hydrogen-bond basicity (), for the binary mixtures of several imidazolium-based chloride ILs plus either dipolar protic solvents (water and methanol) or dipolar aprotic solvents (dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile). The results demonstrated that those parameters could be altered by the structure of IL and type of co-solvent owing to the solute-solvent and solventsolvent interactions. The structure of alkyl chain of cation had considerable impact on the * variation of IL aqueous solution against IL concentration but hardly affected other mixtures. Moreover, remarkable preferential solvation of probes was observed for and in the mixtures of IL and dipolar aprotic co-solvents, whereas the hydrogen-bond interactions between IL and dipolar protic co-solvent enabled the preferential solvation to be alleviated and resulted in more linear variation of and against the molar fraction of IL. The results not only contribute to a better understanding of the effect of co-solvent on imidazolium-based chloride ILs, but also are instructive for improving the thermodynamic performance of IL-based applications via providing IL+co-solvent mixtures with desirable physicochemical properties.
Green Chemistry, 2001
A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion. In the series of RTILs studied here, the choice of anion determines water miscibility and has the most dramatic effect on the properties. Hydrophilic anions (e.g., chloride and iodide) produce ionic liquids that are miscible in any proportion with water but, upon the removal of some water from the solution, illustrate how sensitive the physical properties are to a change in water content. In comparison, for ionic liquids containing more hydrophobic anions (e.g., PF 6 2 and N(SO 2 CF 3 ) 2 2 ), the removal of water has a smaller affect on the resulting properties. For a series of 1-alkyl-3-methylimidazolium cations, increasing the alkyl chain length from butyl to hexyl to octyl increases the hydrophobicity and the viscosities of the ionic liquids increase, whereas densities and surface tension values decrease. Thermal analyses indicate high temperatures are attainable prior to decomposition and DSC studies reveal a glass transition for several samples. ILs incorporating PF 6 2 have been used in liquid/liquid partitioning of organic molecules from water and the results for two of these are also discussed here. On a cautionary note, the chemistry of the individual cations and anions of the ILs should not be overlooked as, in the case of certain conditions for PF 6 2 ILs, contact with an aqueous phase may result in slow hydrolysis of the PF 6 2 with the concomitant release of HF and other species.