Thermodynamic Study of Aggregation of Cholinium Perfluoroalkanoate Ionic Liquids

To advance the ionic liquid (IL) platform to tailor fluorinated surfactant properties, the aim of this work is to evaluate the surfactant properties of cholinium-based salts bearing perfluoroalkanoate anions. Novel surfactant ILs containing the cholinium cation [Ch]⁺ combined with different perfluoroalkanoate anions, namely perfluoropentanoate [PFPent]⁻, perfluorohexanoate [PFHex]⁻, perfluoroheptanoate [PFHept]⁻, and perfluorooctanoate [PFOct]⁻, were synthesized. The critical micelle concentrations (CMCs) were determined using an ionic conductivity method, at different temperatures. Thermodynamic parameters of micellization were also evaluated. The results indicate that the CMC value decreases in a linear manner with the increment of the fluoroalkyl chain length in the anion. The evaluation of the thermodynamic parameters shows that the micellization is spontaneous and entropically driven and that the enthalpy of micellization is very small. It was also observed that the introduction of the cholinium cation in these surfactants allows for smaller CMC values when compared to that of other tetraalkylammonium-based surfactants with the same fluorinated anions, in short to more efficient and green surfactants. This result is probably due to counterion association and not to counterion binding to micelle surface

Removal of Nonsteroidal Anti-Inflammatory Drugs from Aqueous Environments with Reusable Ionic-Liquid-Based Systems

In the current era of human life, we face an increased consumption of nonsteroidal anti-inflammatory drugs (NSAIDs). Nevertheless, NSAIDs are not entirely metabolized by humans and are thus excreted into domestical effluents, whereas expired medications are recurrently directly disposed into wastewaters. Several studies have already demonstrated that an extensive diversity of pharmaceuticals is present in aqueous effluents and is therefore a matter of serious concern with regard to wildlife and public health. In this perspective, this work is focused on the use of a liquid–liquid extraction approach for the removal of NSAIDs from aqueous media. In particular, aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and aluminum-based salts were used for the removal of diclofenac, ibuprofen, naproxen, and ketoprofen. With these systems, extraction efficiencies of NSAIDs up to 100% into the IL-rich phase were obtained in a single-step. Further, the recovery of NSAIDs from the IL medium and the recyclability of the IL-rich phase were ascertained aiming at developing a more sustainable and cost-effective strategy. On the basis of the remarkable increase of the NSAIDs solubility in the IL-rich phase (from 300- to 4100-fold when compared with pure water), water was used as an effective antisolvent, where recovery percentages of NSAIDs from the IL-rich phase up to 91% were obtained. After the “cleaning” of the IL-rich phase by the induced precipitation of NSAIDs, the phase-forming components were recovered and reused in four consecutive cycles, with no detected losses on both the extraction efficiency and recovery of NSAIDs

Influence of Different Inorganic Salts on the Ionicity and Thermophysical Properties of 1‑Ethyl-3-methylimidazolium Acetate Ionic Liquid

The ionicity of ionic liquids (IL) is related to the ionic nature of these fluids and is a useful indicator of the characteristic properties of a given ionic liquid. In this work, we studied the effects caused by the addition of different inorganic salts (IS), on the ionicity of the ionic liquid 1-ethyl-3-methylimidazolium acetate. The solubility of different inorganic salts, based on the ammonium and the sodium cations, in this IL at room temperature was experimentally determined. Thermophysical properties, such as viscosity, density, conductivity, and refractive indexes, of the 1-ethyl-3-methylimidazolium acetate + inorganic salt mixtures were measured in different concentrations of IS, and the ionicity of the systems was calculated. The results showed that when ammonium-based salts are used, the ionicity of the ionic liquid can be increased, leading to the formation of high ionicity ionic liquids

Density, Viscosity, and Refractive Index of Ionic Liquid Mixtures Containing Cyano and Amino Acid-Based Anions

In this work, mixtures of five ionic liquids (ILs) based on a common cation, 1-ethyl-3-methylimidazolium ([C₂mim]⁺), and amino acid anions, namely glycinate ([Gly]⁻), l-alaninate ([l-Ala]⁻), taurinate ([Tau]⁻), l-serinate ([l-Ser]⁻), and l-prolinate ([l-Pro]⁻) with 1-ethyl-3-methylimidazolium tricyanomethane, [C₂mim]­[C­(CN)₃], were prepared. The thermophysical properties, namely density, viscosity, and refractive index, of the neat ILs and their mixtures were measured in the temperature range of <i>T</i> = (293.15 up to 353.15) K. The thermal expansion coefficients were calculated for the neat ILs and were considered to be independent of temperature in the working temperature range. Overall, experimental density, viscosity, and refractive index data of the neat AAILs were in a good agreement with those reported in literature. A dramatic decrease in the viscosity was observed for the IL mixtures as the [C₂mim]­[C­(CN)₃] content increased. The obtained results indicate that mixing [C₂mim]­[C­(CN)₃] with amino acid-based ILs is a potential mean to further increase flexibility and the fine-tune capacity of the physical and chemical properties of amino acid-based ILs

Deep Eutectic Solvents as Azeotrope Breakers: Liquid–Liquid Extraction and COSMO-RS Prediction

The efficient and sustainable separation of azeotropic mixtures remains a challenge in chemical engineering. In this work, the performance of benign solvents, namely deep eutectic solvents (DES), in the separation of aromatic–aliphatic hydrocarbon azeotropic mixtures via liquid–liquid extraction (LLE) was evaluated. The DES studied in this work were based on different ammonium salts (cholinium chloride, [Ch]­Cl, benzylcholinium chloride, [BzCh]­Cl, and tetrabutylammonium chloride, [N₄₄₄₄]­Cl) as hydrogen bond acceptor (HBA) and one organic acid (levulinic acid, LevA) as hydrogen bond donor (HBD), always in the mole ratio of 1 HBA:2 HBD. The thermophysical properties, namely density and viscosity, of the three used DES were measured in the temperature range <i>T</i> = (293.15 up to 353.15) K and at atmospheric pressure. The phase equilibria diagrams of all ternary systems were determined at <i>T</i> = 298.15 K and at atmospheric pressure using ¹H NMR spectroscopy. The results showed that the introduction of a more hydrophobic HBA in the DES promotes the improvement of the distribution coefficient, while playing with the aromaticity of the DES leads to higher selectivity. In addition, the performance of the predictive conductor-like screening model for real solvent (COSMO-RS) model in the description of these systems was also evaluated. COSMO-RS is capable of quantitatively predicting the phase behavior and tie-lines for ternary mixtures containing DES as well as of estimating the trend of distribution ratio and selectivity

Improving the Separation of <i>n</i>‑Heptane + Ethanol Azeotropic Mixtures Combining Ionic Liquid 1‑Ethyl-3-methylimidazolium Acetate with Different Inorganic Salts

In this work, the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate, [C₂MIM]­[Ac], was combined with the inorganic salts (ISs) ammonium acetate, [NH₄]­[Ac], ammonium chloride, [NH₄]­Cl, and ammonium thiocyanate, [NH₄]­[SCN], and used as an extraction solvent for the separation of the azeotropic mixture of <i>n</i>-heptane + ethanol. The liquid–liquid equilibria (LLE) of the ternary mixtures of <i>n</i>-heptane + ethanol + IL or IL-IS was experimentally measured at 298.15 K and 0.1 MPa. The feasibility of the extraction solvents was assessed by the distribution coefficient and the selectivity. The results showed that the extraction solvents studied can be suitable candidates for the separation of ethanol from <i>n</i>-heptane. Additionally, we show that the solubilization of ISs in the IL can greatly increase the selectivity of the latter, while no significant impact on the distribution coefficient is verified. Moreover, the distribution coefficient values obtained for the [C₂MIM]­[Ac] and its mixtures with ISs are the highest among neat ILs tested so far for the azeotropic mixture in study. The experimental liquid–liquid equilibrium data were correlated using the nonrandom two-liquid (NRTL) excess Gibbs free energy model

Fatty Acids-Based Eutectic Solvents Liquid Membranes for Removal of Sodium Diclofenac from Water

Nowadays, the scarcity of clean fresh water is a major concern to public health. One of the main issues linked with this topic is the unavoidable contamination of water bodies with active pharmaceutical ingredients, which results from production and metabolization of prescribed and over the counter drugs closely related to human health and wellbeing. As the currently available techniques for removal of micropollutants (MPs) from wastewater are not sufficiently broad, efficient, and cost effective, new sustainable alternatives are required to prevent the contamination of water bodies which can compromise the viability of aquatic ecosystems and, ultimately, life on earth as we know it. Herein, a natural eutectic solvent (ES), based on fatty acids, is proposed to remove important MPs, sodium diclofenac, the most used nonsteroid anti-inflammatory drug, and a plasticizer, Bisphenol A (BPA), through liquid–liquid extraction (LLE), as well as preparation of liquid membranes. The extraction of sodium diclofenac through LLE reached an efficiency of (97 ± 1)% that was maintained when shifting to the liquid membranes while reducing the quantity of solvent to only 1.5% of that required in LLE. These membranes were reused through 10 cycles of extraction without major loss of efficiency. The optimal extraction efficiency of BPA using ES supported in membranes reached (63 ± 1)%. The easy preparation of hydrophobic natural eutectic solvents-based absorbent materials through their impregnation in porous inert supports enables the development of highly efficient and cost-effective adsorption technology for the removal MPs from water

Aqueous Biphasic Systems of Pyrrolidinium Ionic Liquids with Organic Acid-Derived Anions and K₃PO₄

Aqueous biphasic systems based on ionic liquids (ILs) have been researched as promising extraction and purification routes for a huge diversity of compounds. The inherent tunability offered by ILs combined with the large variety of salts available underlines the reliable phase equilibrium data. In this vein, this work presents novel aqueous biphasic systems based on the 1-butyl-1-methylpyrrolidinium cation combined with anions derived from organic acids, such as acetate, trifluoroacetate, hexanoate, adipate, and one halogenated anion, bromide, in the presence of a powerful salting out species, the inorganic salt K₃PO₄. The capacity of these ILs to undergo phase separation is discussed in regard to the chemical structure of the IL anion. The results here obtained were compared with those determined for poly­(ionic liquid) analogues, and it was observed that while in ILs the hydrophobicity of the anion has the major role in phase splitting, in poly­(ionic liquid)­s that role is played by the polymer molecular weight. The effect of temperature on the phase equilibria is addressed

Ionic Liquids as Additives for Extraction of Saponins and Polyphenols from Mate (Ilex paraguariensis) and Tea (Camellia sinensis)

Extracts from plant tissue are a rich source of lead compounds for nutraceutical or pharmaceutical applications. Nevertheless, the concentration of added value compounds in the plants extracts is usually lower than 1–2%. As consequence, a search for new improved, more efficient technologies combined with solvent engineering has emerged in the last years. In this work, we evaluate the performance of ionic liquids (ILs) as additives in the extraction of saponins and polyphenols from tea and mate. Two families of ILs, imidazolium- and cholinium-based, combined with a wide variety of hydrophilic anions, have been tested. The influence of several parameters such as ionic liquid chemical structure, water content, solvent/raw material ratio, temperature, and contact time period was evaluated. The best performing IL in the extraction of saponins and polyphenols was chosen to pursue to the concentration step using ILs-based aqueous biphasic systems (ABS) were tested. Finally, the saponins and polyphenols existent in the ABS IL-rich phase were recovered through the addition of a second more hydrophobic IL

Understanding the Role of Cholinium Carboxylate Ionic Liquids in PEG-Based Aqueous Biphasic Systems

This work aims at exploring new sustainable separation processes based on ionic liquids. Aqueous biphasic systems (ABS) based on poly­(ethylene glycol) (PEG) with low molecular weight (600 and 4000 g mol^–1) and cholinium-based ionic liquids and salts containing anions derived from carboxylic acids (oxalate, malonate, succinate, l-malate, fumarate, glutarate and citrate), available in natural compounds, are here presented. Contrary to common ionic liquids, the cholinium-based ionic liquids used in this work are biodegradable, nontoxic, cheap, and simple to prepare, and PEG is also a cheap and nontoxic phase promoter agent. The data reported in this work allows novel insights into the phase splitting mechanism of these ABSs regarding the influence of alkyl chain length of the anion and the presence of substituent groups in the anion. The effect of PEG molecular weight in the ABS was also addressed. Furthermore, the possible application of these systems for the extraction/separation of antioxidants, namely, <i>tert</i>-butylhydroquinone (TBHQ), was evaluated