Journal of Ionic Liquids最新文献

Ionic liquids have been described as green solvents, however, their presence in the aquatic environment may indicate a threat for key species. Focusing on the freshwater ecosystem, five ionic liquids containing the 1‑butyl‑3-methylimidazolium (BMIM) cation were compared for their acute toxicity and chronic responses on daphnids. Biochemical markers of physiology including the activity of phosphatases, β-galactosidase, peptidase, lipase and glutathione-S-transferase were used to assess changes in physiology of daphnids. Feeding and reproduction were investigated as surrogate phenotypic measures. Feeding rate was decreased in all exposures, and severely impacted in BMIM hexafluorophosphate, chloride, and tetrafluoroborate, while reproduction was unaffected by all ionic liquids. A diverse set of responses were triggered from each BMIM ionic liquid in reference to enzyme activities providing insight for the toxicity impact of these emerging contaminants. Phosphatase activities were significantly decreased in all exposure scenarios to ionic liquids, but different patterns of biochemical responses were documented among acute and chronic exposures and different ionic liquids, indicating distinct mechanistic patterns. The aforementioned results highlight the toxic potential of ionic liquids which are characterised so far as green solvents.

Ionic liquids are modern materials with a broad range of applications, including electrochemical devices, the exploitation of sustainable resources and chemical processing. Expanding the chemical space to include novel ion classes allows for the elucidation of novel structure-property relationships and fine tuning for specific applications. We prepared a set of ionic liquids based on the sparsely investigated pentamethyl guanidinium cation with a 2-ethoxy-ethyl side chain in combination with a series of frequently used anions. The resulting properties are compared to a cation with a pentyl side chain lacking ether functionalization. We measured the thermal transitions and transport properties to estimate the performance and trends of this cation class. The samples with imide-type anions form liquids at ambient temperature, and show good transport properties, comparable to imidazolium or ammonium ionic liquids. Despite the dynamics being significantly accelerated, ether functionalization of the cation favors the formation of crystalline solids. Single crystal structure analysis, ab initio calculations and variable temperature nuclear magnetic resonance measurements (VT-NMR) revealed that cation conformations for the ether- and alkyl-chain-substituted are different in both the solid and liquid states. While ether containing cations adopt compact, curled structures, those with pentyl side chains are linear. The Eyring plot revealed that the curled conformation is accompanied by a higher activation energy for rotation around the carbon-nitrogen bonds, due to the coordination of the ether chain as observed by VT-NMR.

Biopolymers are natural macromolecules obtained from animal, plant and microbial sources, with the potential to be used in a wide range of applications. A key process step, which is still underdeveloped, is the downstream processing. In this work, water immiscible and water miscible ionic liquids (ILs) were investigated regarding their ability to fractionate a mixture of polysaccharide and proteins. Alginate and bovine serum albumin (BSA) were used as model compounds to mimic natural polymer crude extract. Phosphonium ILs composed of different anions (bromide, dicyanamide and phosphinate) were used as water immiscible ILs while imidazolium ILs, combined with phosphate salts to form biphasic system, were selected as water miscible ILs. In water immiscible IL systems, the partitioning behavior of biopolymers depended on IL's anions and there was formation of insoluble precipitate. The insolubility of precipitate in diverse aqueous and organic solvents hindered the processibility of water immiscible phosphonium IL for fractionation of biopolymers. The partitioning of biopolymers in water miscible ILs systems also depended on the IL's anion, as well the concentration of IL. Separation of alginate (yield = 90% and purity = 99%) from BSA (yield = 89% and purity = 99%) was best achieved by the [C₄mim]Cl-based extraction system. After fractionation, regeneration of IL and salt used was carried out by ultrafiltration, with recovery yields up to 100%. The high extraction yields and recyclability of phase-forming compounds confirm the potential of water miscible ILs systems to fractionate polysaccharide and protein.

Electrolytic conductivity measurements for a total of ten ionic liquids (ILs) (four N-alkyl-N-methyl pyrrolidinium cations [C_nmpyr] and six 1-(methyl)benzyl-3-alkyl imidazolium cations ([Bnmim] or [MeBnC_nmim]), all paired with bistriflimide [Tf₂N] anions) are reported at p = 0.1 MPa over T = 293.15 – 323.15 K. All samples were thoroughly dried under vacuum and their water content before and after measurements was determined by Karl Fischer titration. For the conductivity measurements, an impedance bridge technique was used in conjunction with a sealed cell equipped with platinum black electrodes. The cell constant (K_cell = 101 m ^− 1) was determined with standard aqueous KCl solutions before and after measurements. The results show that electrolytic conductivity increases with increasing temperature in both families of ILs, while conductivity decreases as the length of the IL side chain increases, which is associated with increase in IL viscosity. Conductivities of the pyrrolidinium ILs were consistent with other data for these compounds already reported in the literature. The conductivities of the 1-(methyl)benzyl-3-alkyl imidazolium ILs are reduced by ∼70-90% compared to the analogous 1-alkyl-3-methylimidazolium ILs

Ionic liquid (IL) catalysed organic syntheses have emerged as a great approach to improve synthetic productivity. Particularly IL catalyzed domino reactions enable the synthesis of organic compounds with high regio/stereoselectivity from simple starting materials. Being the designer solvents, IL promoted domino reactions lead to the eco-friendly green synthetic steps with high-percentage yield. In this review, we have summarized the IL catalyzed one pot tandem reactions for the synthesis of highly functionalized organic molecules. The reaction mechanisms, regioselectivity, and stereoselectivity of the reactions are described in detail. This review has been summarized to extend the synthetic applications of IL catalyzed domino reactions in future.

In this study a liquid-liquid extraction (LLX) process has been investigated based on experimental analysis and kinetic modelling. The purpose of this investigation is (1) to understand the mass transfer behaviour, (2) to determine the rate limiting step via evaluating different mass transfer models, and (3) to estimate the mass transfer and kinetic parameters. This has been discussed in the context of the extraction of Co by the ionic liquid (IL) [P₈₈₈₈][Oleate] as an example of LLX with chemical reaction. Mass transfer models, with and without a chemical reaction, are evaluated based on a statistical cross-validation method. The following operational parameters are included in the analysis: column lengths, droplet diameter, droplet rising velocity and continuous and dispersed phase concentrations on Co uptake. This method reveals that a single parameter representing the external mass transfer resistance can describe the forward extraction of Co (i.e., into the IL) for the whole data set sufficiently accurate (error ±30%) regardless of the studied operational conditions. Back-extraction of Co from pre-loaded IL droplets shows a different transfer mechanism. Now the mass transfer in the dispersed IL phase dominates the process which is attributed to a change of the physical properties of the pre-loaded IL.

Ionic liquids are materials composed purely of cations and anions which melt at or below 100 ${}^{\circ }$C. For applications involving wetting of a solid surface by an ionic liquid or the flow of ionic liquid through capillaries, one must know the wetting properties of the ionic liquid/solid pair, such as the contact angle ($\theta$). Herein, the use of a (numerical) theoretical model of capillary rise kinetics for describing the experimental data of meniscus height versus time for a particular ionic liquid (BMI.BF${}_4$) rising in a glass capillary tube is reported, assessing also the suitability of estimating the ionic liquid/glass contact angle ($\theta$) from the fitting procedure involved. Capillary rise experiments were conducted in glass capillaries with 1 mm internal diameter and digital images from the corresponding videos (obtained with an smartphone high-resolution camera and a LED light box) were semi-automatically processed/analyzed using an algorithm (script) specifically developed for such purpose. A relatively good agreement between the experimental data and the theoretical predictions was found for the ionic liquid (BMI.BF${}_4$) studied, in particular with respect to the shape of the height versus time curve. From fitting the theoretical model to the experimental data, a value of $43.7\pm 6.4^{\circ }$ was obtained for the contact angle ($\theta$) of BMI.BF${}_4$ in glass at a temperature of $23.7\pm 0.4^{\circ }$C. The results obtained validated the utilized methodology for determining the contact angle of ionic liquids in (transparent) solid surfaces and also showed its adequacy for studying the kinetics of capillary rise of such liquids in small vertical capillaries.

In the context of the current environmental issues and the need to consolidate effective efforts according to the criteria of a circular economy, adsorption of copper from water with functionalized materials has shown high performance at low cost. However, desorption requires high amounts of acid and base to regenerate the functionalized material. In order to overcome this drawback, this work proposes an alternative desorbing phase based on a specific extractant for copper 1,1,1-trifluoro-2,4-pentanodione (TFA) dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. In this way, adsorption experiments were carried out using adsorbent fly ash, modified with a mesoporous siliceous material, and functionalized with 3-aminopropyl-triethoxysilane (APS). Under the operating conditions of this study, the best desorption performance was achieved using the lowest functionalization percentage of the absorbent material. The desorption percentage reached 45% after 200 min of contact with a stirred solution of TFA 0.2 [M] in IL. This percentage can be increased to around 70% through a second contact with fresh desorbing phase. Meanwhile, the conventional desorption technique with nitric acid showed faster kinetics and a slightly higher desorption percentage close to 50%. In turn, the final pH of the adsorbent slightly decreased when the proposed desorbing phase was used, representing an advantage over the use of acid. Additionally, it was possible to decrease the amount of desorbing phase allowing the concentration of copper. The COSMO-RS calculations indicate that a more hydrophobic IL could increase desorption percentage.

The manuscript “Ionic Liquid Induced p-Nitrophenol Prototropism” deals with the acid-base properties of p-Nitrophenol molecule in the presence of two different Ionic Liquids (ILs). Prototropic equilibria of p-Nitrophenol (PNP) have been studied in water, ethanol, carbon tetrachloride, chloroform, cyclohexane and IL added aqueous solution with the help of Uv-vis absorbance spectroscopy. It was found that PNP mainly exists in neutral form when dissolved in ethanol, carbon tetrachloride, chloroform and cyclohexane. Interestingly, ground state ionization of PNP takes place in water and results into the formation of p-Nitrophenolate anion as a result of proton transfer to water and hence two absorbing species have been detected in the absorbance spectra. Inter-conversion of neutral to anionic and vice versa can be achieved with the addition of small amount of NaOH/HCl. Furthermore, in water/ethanol binary mixture both neutral and anionic forms exist. Interactions of surfactants sodium dodecyl sulfate (SDS) and cetrimonium bromide (CTAB) with neutral and ionic forms of PNP is also explored. To assess the potential role of ILs as a solubilizing media that facilitates proton-transfer reactions, p-Nitrophenol prototropism is investigated in water in the presence of small amount of added ILs. Interestingly, addition of small amount of hydrophilic IL, 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF₄] or hydrophobic IL, 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF₆] into PNP dissolved in high pH water causes protonation of the already present p-Nitrophenolate anion. Protonation of p-Nitrophenolate is attributed due to presence of acidic C2-H protons in [bmim]⁺ cations associated with both ILs. Furthermore, the extent of protonation induced by addition of [BF₄]⁻ based IL is found to be much pronounced as compared to [PF₆]⁻ based IL having same cation due to difference in hydrolytic properties of [BF₄]⁻ based ILs when compared with [PF₆]⁻ based ILs. These findings could contribute to the technological applications for detection, removal and sensing of environmentally hazardous p-Nitrophenol and its ionic forms from water. The results presented in this work lead to a better understanding of prototropic behavior of PNP in IL based media as well as different organic solvents based media.