Separation of Ethanol−Heptane Azeotropic Mixtures by Solvent Extraction with an Ionic Liquid

Ionic liquids (ILs) are gaining attention as potential substitutes for classical organic solvents in extraction processes. This article reports the results of a study on the use of the IL 1,3-dimethylimidazolium methyl sulfate ([MMIM][MeSO4]) as an extraction solvent in petrochemical processes for the removal of heptane from its mixtures with ethanol. The separation of heptane and ethanol is valuable but difficult because of the formation of an azeotropic mixture. Knowledge of the liquid−liquid equilibria (LLE) of this mixture is essential for the design of separation techniques. For this reason, the experimental LLE for the ternary system heptane + ethanol + [MMIM][MeSO4] were investigated at 298.15 K. The solvent capacity of [MMIM][MeSO4] was compared with those of other ILs. The extraction process derived from the use of this solvent was simulated using conventional software, and the obtained results are reported. Experimental data were obtained in a laboratory-scale packed-column extraction system for the separation of this azeotropic mixture using [MMIM][MeSO4]. A comparison with the experimental column data for other ILs is included. Moreover, it is concluded that [MMIM][MeSO4] has the highest extraction efficiency. Also, this IL can be recycled, meaning that the separation process results in a vast reduction of energy consumption

Gas Permeation Properties of Fluorinated Ionic Liquids

Despite the increasing amount of research in the ionic liquids field, there are still quite unexplored themes. That is the case of the fluorinated ionic liquids (FILs) family, here defined as ionic liquids with fluorine tags longer than four carbon atoms. In this work, gas permeation properties of two fluorinated ionic liquids, tetrabutylammonium heptadecafluorooctanesulfonate and 1-ethyl-3-methylpyridinium perfluorobutanesulfonate, were studied. For that purpose, supported liquid membranes of the fluorinated ionic liquids were prepared using a polymeric porous membrane as supporting material, and their gas permeation properties for 10 different gases at 294 K were measured using a time-lag apparatus. The results show that the gas solubility of these FILs is of the same order of magnitude as gas solubilities for previously tested fluorinated ionic liquids and that solute size plays a more important role on gas diffusivity than viscosity. The perfluorocarbons and carbon dioxide separation performances were evaluated, and the results show that 1-ethyl-3-methylpyridinium perfluorobutanesulfonate is a better candidate than tetrabutylammonium heptadecafluorooctanesulfonate for the gas separation processes tested in this work

Acute Aquatic Toxicity and Biodegradability of Fluorinated Ionic Liquids

Several novel fluorinated ionic liquids (FILs), fully miscible with water and with excellent surfactant behavior, have been studied for pharmacological applications. The use of these novel FILs as drug delivery systems can improve the bioavailability, stability and efficacy of therapeutic proteins. An initial screening of toxicity in four different human cell lines indicated that some of the FILs possess low cytotoxicity. An environmental hazard assessment of these compounds, in the context of Green Pharmacy, is necessary before a pharmaceutical application takes place. In this work, ecotoxicity tests have been performed in aquatic species with different levels of biological organization (Vibrio fischeri, Daphnia magna and Lemna minor) to evaluate intrinsic hazard that these FILs might pose after being released to the aquatic environment from the human body or from industrial processes. Additionally, the biodegradability of these compounds has been evaluated using microorganisms from wastewater treatment plants

Hydrogen-Bonding and the Dissolution Mechanism of Uracil in an Acetate Ionic Liquid: New Insights from NMR Spectroscopy and Quantum Chemical Calculations

The dissolution of uracil–a pyrimidine nucleic acid base–in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C₂mim]­[CH₃COO]) has been investigated by methods of ¹H and ¹³C NMR spectroscopy, ¹H–¹H NOESY NMR spectroscopy, and quantum chemical calculations. The uracil–[C₂mim]­[CH₃COO] interactions that define the dissolution mechanism comprise the hydrogen bonds between the oxygen atoms of the acetate anion and the hydrogen atoms of the N1–H and N3–H groups of uracil and also the hydrogen bonds between the most acidic aromatic hydrogen atom (H2) of the imidazolium cation and the oxygen atoms of the carbonyl groups of uracil. The bifunctional solvation nature of the ionic liquid can be inferred from the presence of interactions between both ions of the ionic liquid and the uracil molecule. The location of such interaction sites was revealed using NMR data (¹H and ¹³C chemical shifts both in the IL and in the uracil molecule), complemented by DFT calculations. NOESY experiments provided additional evidence concerning the cation–uracil interactions

New Insight into Phase Equilibria Involving Imidazolium Bistriflamide Ionic Liquids and Their Mixtures with Alcohols and Water

The fluid phase equilibria (liquid−liquid demixing behavior (LLE)) of mixtures of ionic liquids of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide family, [Cnmim][NTf2], with 2-methylpropanol or n-octanol were investigated. Binary mixtures of [C4mim][NTf2] + alcohol and [C6mim][NTf2] + alcohol were compared to pseudobinary mixtures of (0.5[C2mim] + 0.5[C6mim])[NTf2] + alcohol and (0.5[C2mim] + 0.5[C10mim])[NTf2] + alcohol, respectively. Additionally, the presence of water in the studied alcohols or as a third component in the system was analyzed in order to check any possible deviation from the LLE observed for the anhydrous systems. Systems containing small fractions of ionic liquid show similar LLE between the corresponding binary and pseudobinary systems; however, large differences are observed in the presence of water when the IL mass fraction is increased

Aggregation Behavior and Total Miscibility of Fluorinated Ionic Liquids in Water

In this work, novel and nontoxic fluorinated ionic liquids (FILs) that are totally miscible in water and could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements, and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry, and surface tension measurements in order to study various thermodynamic and surface properties that demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures

On the Formation of a Third, Nanostructured Domain in Ionic Liquids

The study of solid–fluid transitions in fluorinated ionic liquids using differential scanning calorimetry, rheology, and molecular modeling techniques is an essential step toward the understanding of their dynamics and the thermodynamics and the development of potential applications. Two fluorinated ionic liquids were studied: 1-hexyl-3-methylimidazolium perfluorobutanesulfonate, HMIm­(PFBu)­SO3, and tetrabutylammonium perfluorobutanesulfonate, NB4(PFBu)­SO3. The experimental calorimetric and rheological data were analyzed taking into account the possible mesoscale structure of the two fluorinated ionic liquids. The simulation results indicate the possible formation of three nanosegregated domainspolar, nonpolar, and fluorousthat may have a profound impact on ionic liquid research. In the case of HMIm (PFBu)­SO3 the three types of mesoscopic domains can act as interchangeable jigsaw pieces enabling the formation of multiple types of crystals and inducing the observed calorimetry and rheological trends

Physicochemical Characterization of Ionic Liquid Binary Mixtures Containing 1‑Butyl-3-methylimidazolium as the Common Cation

Mixing ionic liquids (as well as mixing an inorganic salt in an ionic liquid) constitutes an easy, elegant methodology for obtaining new ionic materials. In this study, 3 ionic liquids (ILs) sharing a common cation were synthesized and mixed in 9 different proportions giving rise to 27 binary mixtures. Specifically, 1-butyl-3-methyl­imida­zolium nitrate, [C4C1Im]­[NO3], 1-butyl-3-methyl­imida­zolium chloride, [C4C1Im]­Cl, and 1-butyl-3-methyl­imidazolium methane­sulfonate, [C4C1Im]­[CH3SO3], were synthesized and characterized. They all share 1-butyl-3-methyl­imida­zolium as the common archetypal cation. None of them (or any of their binary mixtures) is liquid at room temperature (T = 298.15 K), and two of them are only in the liquid state above temperatures of 343–353 K. Despite belonging to commonly used families of ILs, their handling and the study of their liquid properties (neat and mixtures) have become particularly difficult, mainly because of their tendency to solidify and their high viscosity (caused by hydrogen-bonded networks). The main goal of this work is to evaluate the thermal, dynamic, and volumetric properties of these compounds and their mixtures as well as the solid–liquid equilibria of their binary mixtures. Thermal properties, such as melting and glass-transition temperatures, were determined or calculated. Therefore, both density and viscosity have been measured and were used for the calculation of the isobaric thermal expansion coefficient, molar volumes, excess molar volumes, and viscosity deviations to linearity

Fluorinated Ionic Liquids: Properties and Applications

Ionic liquids have become a green media for engineering applications due to exceptional physicochemical properties, such as their practically nonvolatile nature, null flammability, low melting point, high ionic conductivity, and thermal and electrochemical stability. This work aimed to select the best fluorinated ionic liquids for the following applications: recovery/recycling of perfluorocarbon contaminants such as greenhouse perfluorocarbons gases and perfluoroalkyl acids of industrial effluents that are persistent, bioaccumulative, and toxic, and the partial or total replacement of inert perfluorocarbons in oxygen therapeutic emulsions by enhancing the emulsion stability and increasing the solubility of respiratory gas. With this dual goal in mind, thermodynamic and thermophysical properties of fluorinated ionic liquids (FILs) and their toxicity and biocompatibility are discussed so that the feasibility of the proposed applications can be evaluated. Herein, FILs are defined as ionic liquids with fluorinated chain lengths equal or greater than four carbon atoms. This paper provides a critical review of the experimental data for fluorinated ionic liquids available in the literature, and subsequently, with the aim of expanding knowledge of FILs, eight new fluorinated ionic liquids were selected for characterization. The attained results will clearly impact applications using polyfluorinated compounds