Binary Mixtures of Ionic Liquids in Aqueous Solution: Towards an Understanding of Their Salting-In/Salting-Out Phenomena (original) (raw)
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The Journal of Physical Chemistry B, 2009
The understanding of the specific interactions between salt ions and ionic liquids (ILs) in aqueous solutions is relevant in multiple applications. The influence of a series of anions on the solubility of 1-butyl-3methylimidazolium tricyanomethane in aqueous environment was here studied. This study aims at gathering further information to evaluate the recently proposed 1,2 mechanisms of salting-in-and salting-out-inducing ions in aqueous solutions of ILs and to provide insights at the molecular-level on the phenomena occurring in these systems. The observed effect of the inorganic species on the aqueous solubility of the ionic liquid qualitatively follows the Hofmeister series, and it is dependent on the nature and concentration of the anions. The liquid-liquid equilibrium data and 1 H NMR results here reported support a model according to which salting-in-and salting-out-inducing ions operate by essentially different mechanisms. While salting-out is an entropically driven effect resulting from the formation of hydration complexes and the increase of the surface tension of cavity formation, the salting-in phenomena is a consequence of the direct binding of the ions to the hydrophobic moieties of the IL. Further evidence here obtained suggests that the interactions of the inorganic ions are not only established with the cation of the IL, but also with the anion, with the observed solubility effect the result of a balance between those two types of interactions.
The present work focussed on application of the environmental friendly 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([BMIM] + [Tf 2 N] − ) ionic liquid for the separations of (alkane/aromatic), (alkane/alk-1-ene), (cycloalkane/aromatic) and (water/alkan-1-ol) using gas-liquid chromatography (GLC) technique. In this reason the activity coefficients at infinite dilution, γ 13 ∞ , for 31 organic solutes (alkanes, cycloalkanes, alkenes, alkynes, aromatics, alkanol and ketones) and water in ionic liquid were measured at temperatures of (323.15, 333.15, 343.15, 353.15 and 363.15) K. Stationary phase loadings of (42.83 and 68.66) % by mass were used to ensure repeatability of measurements. Density and viscosity values were measured to confirm the purity of ionic liquid. Partial molar excess enthalpies at infinite dilution, ΔH 1 E,∞
Predicting the ionicity of ionic liquids in binary mixtures based on solubility data: II
Fluid Phase Equilibria, 2023
"Ionic liquids (ILs) have been deeply investigated as possible substitutes for hazardous organic solvents, but their recently acknowledged ionicity, together with their generally high viscosity, has been hampering their further application. The ionicity (or degree of dissociation) of electrolytes affects properties such as viscosity, solubility and density, so it is of the utmost importance for the proper thermodynamic description of systems containing electrolytes. However, the experimental quantifications of this property are difficult to perform, which creates the need for more predictive approaches. In this work, the ionicity of 12 ionic liquids in binary mixtures composed of water, ethanol, 1-propanol or 1-butanol was predicted based on solubility data available in literature by the Pitzer-Debye-Hückel (PDH) equation combined with the UNIversal QUAsi-Chemical (UNIQUAC) model, which is often referred as PDH+UNIQUAC. The ionicity of the ionic liquids was modelled as function of mole composition for a total of 17 binary systems, comprising ILs of three chemical families: hexafluorophosphates, tetrafluoroborates, and bis(trifluoromethylsulfonyl)imides, continuing a previous work. This novel methodology provided a useful tool to estimate the ionicity of ionic liquids containing imidazolium cations without undergoing long experimental determinations, which could be applied in the design of separation processes."
Physical chemistry chemical physics : PCCP, 2015
Due to scarce available experimental data, as well as due to the absence of predictive models, the influence of salts on the solubility of ionic liquids (ILs) in water is still poorly understood. To this end, this work addresses the solubility of the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C1im][NTf2]), at 298.15 K and 0.1 MPa, in aqueous salt solutions (from 0.1 to 1.5 mol kg(-1)). At salt molalities higher than 0.2 mol kg(-1), all salts caused salting-out of [C4C1im][NTf2] from aqueous solution with their strength decreasing in the following order: Al2(SO4)3 > ZnSO4 > K3C6H5O7 > KNaC4H4O6 > K3PO4 > Mg(CH3CO2)2 > K2HPO4 > MgSO4 > KH2PO4 > KCH3CO2. Some of these salts lead however to the salting-in of [C4C1im][NTf2] in aqueous medium at salt molalities lower than 0.2 mol kg(-1). To attempt the development of a model able to describe the salt effects, comprising both the salting-in and salting-out phenomena observed, the electro...
2014
The knowledge of the liquid-liquid equilibria (LLE) between ionic liquids (ILs) and water is of utmost importance for environmental monitoring, process design and optimization. Therefore, in this work, the mutual solubilities with water, for the ILs combining the 1-methylimidazolium, [C 1 im] + ; 1-ethylimidazolium, [C 2 im] + ; 1-ethyl-3-propylimidazolium, [C 2 C 3 im] + ; and 1-butyl-2,3-dimethylimidazolium, [C 4 C 1 C 1 im] + cations with the bis(trifluoromethylsulfonyl)imide anion, were determined and compared with the isomers of the symmetric 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ([C n C n im][NTf 2 ], with n = 1-3) and of the asymmetric 1-alkyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide ([C n C 1 im][NTf 2 ], with n = 2-5) series of ILs. The results obtained provide a broad picture of the impact of the IL cation structural isomerism, including the number of alkyl side chains at the cation, on the water-IL mutual solubilities. Despite the hydrophobic behaviour associated to the [NTf 2 ] − anion, the results show a significant solubility of water in the IL-rich phase, while the solubility of ILs in the water-rich phase is much lower. The thermodynamic properties of solution indicate that the solubility of ILs in water is entropically driven and highly influenced by the cation size. Using the results obtained here in addition to literature data, a correlation between the solubility of [NTf 2 ]-based ILs in water and their molar volume, for a large range of cations, is proposed. The COnductor like Screening MOdel for Real Solvents (COSMO-RS) was also used to estimate the LLE of the investigated systems and proved to be a useful predictive tool for the a priori screening of ILs aiming at finding suitable candidates before extensive experimental measurements.
The Journal of Chemical Thermodynamics, 2012
(Liquid + liquid) equilibrium data for the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMim][NTf 2 ], 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [PMim] [NTf 2 ], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMim][NTf 2 ], and 1-hexyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide, [HMim][NTf 2 ], mixed with ethanol and heptane were studied at T = 298.15 K and atmospheric pressure. The ability of these ionic liquids as solvents for the extraction of ethanol from heptane was evaluated in terms of selectivity and solute distribution ratio. Moreover, density and refractive index values over the miscible region for the ternary mixtures were also measured at T = 313.15 K. Finally, the experimental data were correlated with the Non Random Two Liquids (NRTL) and UNIversal QUAsi Chemical (UNIQUAC) thermodynamic models, and an exhaustive comparison with available literature data of the studied systems was carried out.
Fluid Phase Equilibria, 2009
The activity coefficients at infinite dilution, γ 13 ∞ for 32 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, tetrahydrofurane, tert-butyl methyl ether, and water in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][CF 3 SO 3 ] were determined by gas-liquid chromatography at the temperatures from 298.15 to 368.15 K. The partial molar excess enthalpies at infinite dilution values ∆H 1 E,∞ were calculated from the experimental γ 13 ∞ values obtained over the temperature range. The selectivities for the hexane/benzene, cyclohexane/benzene, n-hexane/thiophene, n-decane/thiophene, cyclohexane/thiophene, toluene/thiophene, and oct-1-ene/thiophene separation problems were calculated from the γ 13 ∞. Obtained values were compared to the literature values for the other ionic liquids, NMP, and sulfolane.
Arabian Journal of Chemistry, 2014
This article principally reviews our research related to liquid-liquid and solid-liquid phase behavior of imidazolium-and phosphonium-based ionic liquids, mainly having bistriflamide ([NTf 2 ] À ) or triflate ([OTf] À ) anions, with several aliphatic and aromatic solutes (target molecules). The latter include: (i) diols and triols: 1,2-propanediol, 1,3-propanediol and glycerol; (ii) polymer poly(ethylene glycol) (PEG): average molecular mass 200, 400 and 2050 -PEG200 (liquid), PEG400 (liquid) and PEG2050 (solid), respectively; (iii) polar aromatic compounds: nicotine, aniline, phenolic acids (vanillic, ferulic and caffeic acid,), thymol and caffeine and (iv) non-polar aromatic compounds (benzene, toluene, p-xylene). In these studies, the effects of the cation and anion, cation alkyl chain and PEG chain lengths on the observed phase behaviors were scrutinized. Thus, one of the major observations is that the anion -bistriflamide/triflate -selection usually had strong, sometimes really remarkable effects on the solvent abilities of the studied ionic liquids. Namely, in the case of the hydrogen-bonding solutes, the ionic liquids with the triflate anion generally exhibited substantially higher solubility than those having the bistriflamide anion. Nevertheless, with the aromatic compounds the situation was the opposite -in most of the cases it was the bistriflamide anion that favoured solubility. Moreover, our other studies confirmed the ability of PEG to dissolve both polar and non-polar aromatic compounds. Therefore, two general possibilities of application of alternative, environmentally acceptable, solvents of tuneable solvent properties appeared. One is
This work focusses on the application and pre-screening of selected ILs for different industrial separation problems based on limiting activity coefficients at infinite dilution, and liquid-liquid equilibrium data at different temperatures. The selected ionic liquids for pre-screening based on activity coefficients at infinite dilution data include (1,3- dimethyimidazolium dimethylphosphate, trioctylmethylammonium chloride, trihexyltetradecylphosphonium dicyanamide, 2,3-dihydroxypropyl-N-methyl-2- oxopyrrolidinium chloride, 2,3-epoxypropyl methyl-2-oxopyrrolidinium chloride) and deep eutectic solvent (1-butyl-3-methylimidazolium chloride + glycerol) at 1:2 molar ratio. These ionic liquids were tested in 33 solutes (alkanes, alkenes, alkynes, alcohols, tetrahydrofuran, ketones, aromatic hydrocarbons, thiophene, acetonitrile) and water at T = (313 – 343) K and at p = 101 kPa. The use of ionic liquid as a stationary phase on the column loading ranged between (30 – 36) % by mass. Thermo...
The Journal of chemical physics, 2018
The miscibility of ionic liquid (IL) pairs with a common cation (1-ethyl-3-methylimidazolium [CCim]) and different anions (bis(trifluoromethylsulfonyl)amide [TFSI], acetate [OAc], and chloride [Cl]) was investigated at a wide range of water concentrations at room temperature. Molecular simulations predicted that the addition of water to the [CCim][TFSI]:[CCim][OAc] and [CCim][TFSI]:[CCim][Cl] mixtures would induce a liquid-liquid phase separation and that water addition to the [CCim][OAc]:[CCim][Cl] mixture would not produce a phase separation. The effect of water on the phase behavior of the IL mixtures was verified experimentally, and the IL and water concentrations were determined in each phase. Of particular importance is the analytical methodology used to determine the species' concentration, where H NMR and a combination of F NMR, Karl Fischer titration, and ion chromatography techniques were applied.