Ionic Liquid Concentration Research Articles

The Role of Imidazolium 2-Cyanopyrrolide Ionic Liquid in Reduction of CO2 to CO, Formate, and Ethylene on Copper Electrode Revealed By SERS

Electrochemical conversion of CO2 over copper catalyst is known to produce higher value products such as methane, ethylene, formate and alcohols in aqueous electrolytes. Since CO2 is a stable molecule, the electrochemical reduction reaction requires significant overpotential (-1.9 V vs SHE) for the first electron transfer to form CO2 -. Ionic liquids (ILs) have high CO2 solubility and can be further functionalized to bind with CO2 such that CO2 can be brought to the electrode surface in a more reactive state. In this study, we studied electroreduction of CO2 over copper in non-aqueous electrolyte with the reactive IL 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]) in the concentration range of 0.1 to 1 M. The linear sweep voltammetry experiments show the absence of a noticeable Faradic current within the potential window of -1.8 to -2.2 V vs Ag/Ag+ under N2 demonstrating the stability of the imidazolium cation against electrochemical conversion, which is also confirmed by NMR analysis. In the presence of CO2, the onset potential of reduction is at -1.9 V vs Ag/Ag+ (-1.4 V vs. SHE) and does not change with IL concentration. By employing surface enhanced Raman spectroscopy (SERS), potential dependent changes in the interfacial microenvironment during CO2 reduction was revealed. Specifically, imidazolium enrichment and surface adsorbed CO formation were captured. These results confirmed the catalytic role of the IL by facilitating the transport of the reactive CO2 to the electrode surface via imidazolium in particular. On the other hand, surface coverage by imidazolium cations on the electrode seems to prohibit higher level of C-C couplings, thus limiting reaction products to C1 and C2 products. During 3 hrs of bulk electrolysis at -2.1 V (vs. Ag/Ag+) in an H-cell with non-aqueous negolyte containing the IL and an aqueous posolyte (proton source), gaseous products of CO and H2, liquid product of HCOO- and dissolved C2H4were determined by GC and NMR analysis, respectively. Oxidation of Cu electrode was separately captured by ex-situ XPS measurements after 3 hrs of bulk electrolysis. Even though high CO2 concentrations are achieved in ILs and they are stable at CO2 reduction conditions even after 3 hours on Cu surface, IL structure should be optimized to allow C-C coupling to obtain C2+ products.

Ionic liquids with reversible photo-induced conductivity regulation in aqueous solution

Stimulus-responsive ionic liquids have gained significant attention for their applications in various areas. Herein, three kinds of azobenzimidazole ionic liquids with reversible photo-induced conductivity regulation were designed and synthesized. The change of electrical conductivity under UV/visible light irradiation in aqueous solution was studied, and the effect of chemical structure and concentration of ionic liquids containing azobenzene to the regulation of photoresponse conductivity were discussed. The results showed that exposing the ionic liquid aqueous solution to ultraviolet light significantly increased its conductivity. Ionic liquids with longer alkyl chains exhibited an even greater increase in conductivity, up to 75.5%. Then under the irradiation of visible light, the electrical conductivity of the solution returned to its initial value. Further exploration of the mechanism of the reversible photo-induced conductivity regulation of azobenzene ionic liquids aqueous solution indicated that this may attributed to the formation/dissociation of ionic liquids aggregates in aqueous solution induced by the isomerization of azobenzene under UV/visible light irradiation and resulted the reversible conductivity regulation. This work provides a way for the molecular designing and performance regulation of photo-responsive ionic liquid and were expected to be applied in devices with photoconductive switching and micro photocontrol properties.

Pathway for Water Transport through Breathable Nanocomposite Membranes of PEBAX with Ionic Liquid [C12C1im]Cl.

Water transport through membranes is an attractive topic among the research dedicated to dehydration processes, microenvironment regulation, or more simply, recovery of freshwater. Herein, an atomistic computer simulation is proposed to provide new insights about a water vapor transport mechanism through PEBAX membranes filled with ionic liquid (IL) [C12C1im]Cl. Starting from experimental evidence that indicates an effective increase in water permeation as the IL is added to the polymer matrix (e.g., up to 85·10-3 (g·m)/(m2·day) at 318.15 K for PEBAX@2533 membranes loaded with 70% of IL), molecular dynamics simulations are proposed to explore the key role of IL in water transport inside membranes. The polar region composed of anions and cationic head groups of the IL is demonstrated to serve as the pathway for water transport through the membrane. Water molecules always stay near the pathway, which becomes wider and thus has a larger water-accessible area with increasing IL concentration. Hence, the diffusion coefficients of water molecules and ions increase as the IL concentration increases. The simulation provides useful indications about a microscopic mechanism that regulates the transport of water vapor through a kind of PEBAX/IL membrane, resulting in full agreement with the experimental evidence.

Ionic liquid-based ultrasonic-assisted extraction coupled with HPLC to analyze isoquercitrin, trifolin and afzelin in Amygdalus persica L. flowers

This study aimed to establish a method for the simultaneous determination of isoquercitrin, trifolin and afzelin in A. persica flowers by high performance liquid chromatography (HPLC) with ionic liquid as extractant and ultrasonic-assisted extraction. The effects of ionic liquid concentration, solid–liquid ratio, number of crushing mesh, ultrasonic time, extraction temperature, and ultrasonic power on the extraction yield of three target compounds were investigated using the extraction yield of target analytes as the index. According to the results of single factor experiment, the Box-Behnken design-response surface methodology (BBD) was used to optimize the extraction method and compared with the traditional extraction method. The results showed that, calibration curves had excellent linearity (R2 > 0.9990) within the test ranges. In combination with other validation data, this method demonstrated good reliability and sensitivity, and can be conveniently used for the quantification of isoquercitrin, trifolin and afzelinin A. persica flowers. And the contents of isoquercitrin, trifolin and afzelin were 64.08, 20.55 and 75.63 μg/g, respectively. The optimal process obtained by BBD was as follows: ionic liquid concentration was 1.0 mol/L, solid–liquid ratio was 1:40 g/ml, mesh sieve was 50 mesh, ultrasonic time was 40 min, extraction temperature was 50 °C, and ultrasonic power was 400 W. Under the optimal conditions, the theoretical predicted total extraction yield of the three target compounds was 159.77 μg/g, which was close to the actual extraction value (160.26 μg/g, n = 3), this result indicating that the optimal process parameters obtained by response surface methodology analysis were accurate and reliable. The method was simple, accurate and rapid for determination the contents of three active ingredients in A. persica flowers.

Experimental investigation on post-combustion CO2 capture for [Bpy][NO3] and MEA aqueous blends with lower regeneration energy

CO2 capture is an important technology to achieve carbon emission reduction. The key is reducing the energy consumption of the CO2 capture process. Ionic liquids (ILs) blended with organic amines can be used as an efficient CO2 absorbent allowing for low regeneration energy consumption. This work proposes the use of N-butylpyridinium nitrate ([Bpy][NO3]) in combination with organic solvents for CO2 capture. The effects of ILs concentration, reboiler load and flue gas concentration on regeneration energy consumption were studied on a continuous pilot unit for absorption-desorption process. The results showed that the CO2 absorption capacity of 30 wt% MEA + 10 wt% [Bpy][NO3] was 0.1308 g CO2/g solvent, higher than monoethanolamine/water, and the CO2 absorption capacity remained at 74.3% after the five cycles. At 40 °C, the viscosity of IL-amine blending solvents before and after absorption was 2.01 and 3.534 mPa·s, respectively, significantly lower than that of the conventional non-aqueous phase absorbent. The continuous absorption-desorption results showed that the capture rate of IL blending reached more than 95%. The regeneration energy consumption is 34.2% lower than the 30 wt% MEA.

Exploring the structural stability of hemoglobin in DBU-based ionic liquids: Insights from spectroscopic investigations

Globular proteins like heme proteins have garnered significant attention owing to their multiple applications in biochemical as well as biophysical processes and are the major functionalities in various pharmaceuticals and health care products. Hemoglobin (Hb), is the widely studied protein in existence and is the most familiar constituent of vertebrate erythrocytes. Protein solubility and stability in aqueous solutions is a major concern to develop therapeutic protein products as the protein lose its activity under unfolded state. Academic and industrial communities have shown great interest in the selection of an apt solvent for biomolecules in suitable biocatalytic applications. Ionic liquids (ILs) have emerged as a suitable cosolvent for the protein molecules by virtue of its high thermal as well as chemical stabilities. Each IL-Protein interaction is specific and generalizing the behaviour is tedious because the same IL can act as both stabilizer and denaturant depending on the external parameters and IL concentration as well. Here in this study, we have synthesized 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) based ILs derived from heterocyclic bases like 1,2,4- triazole, imidazole and morpholine. DBU based ILs are least explored in biomolecule applications but are known for their high thermal stabilities. The interaction of these ILs with hemoglobin was analysed using various spectroscopic techniques including UV–Visible spectroscopy, steady-state fluorescence, Fluorescence Time-Correlated Single Photon Counting (TCSPC), and Dynamic Light Scattering (DLS) to gain better insight into the effects of these ionic liquids on Hb. These results revealed that all the ILs used here are showing Hb friendly behaviour at lower concentrations as it retains the absorbance and fluorescence behaviour of the protein molecule. DLS data explains the solubilization of the Hb molecule, as the ‘z’ average values decreased with periodic addition of the ILs to the system. Quantitative evaluation of the Hb-IL interactions through Benesi-Hildebrand equation suggested that the possibility of complex formations are minimal and this further substantiate that these ILs can act as better cosolvents for Hb in various biochemical reactions.

Evolution of the La(III) ion coordination sphere in ethylammonium nitrate solution upon water addition

A thorough structural study of La(NO3)3 salt solutions in mixtures of the ethylammonium nitrate (EAN) ionic liquid (IL) and water with EAN molar fraction (χEAN) ranging from 0 to 1 has been carried out by means of X-ray absorption spectroscopy (XAS) measurements at the La K-edge and molecular dynamics (MD) simulations. Both the XAS and MD outcomes agree in finding that the composition of the La3+ ion first solvation shell undergoes steadily changes when moving from pure water to pure EAN. Upon increasing of the IL concentration, the La3+ solvation complexes progressively lose water molecules to accommodate more and more nitrate anions, and the ratio between the two ligands continuously changes across the explored composition range. The nitrate ligands coordinate the metal ion only in a monodentate fashion for the lower EAN contents, while the percentage of bidentate nitrates becomes more and more predominant as the EAN concentration increases. When moving from pure water to pure EAN, the La3+ ion coordination passes from a 9-fold tricapped trigonal prismatic geometry to a 12-fold icosahedral one, while a 10-fold coordination with bicapped square antiprism geometry is the dominant species for the mixed compositions. The remarkable flexibility of this solvation complex in accommodating a variable amount of water molecules and nitrate ligands at dependence of the system composition is key for its predominance in all the EAN/water mixtures.

N-doped graphene leaves on carbon nanotubes and NiMn2O4-graphene hybrid nanocomposites with ionogel film for flexible symmetric and asymmetric supercapacitors

The efficient fusion of the various components into hybrid nanostructures in a hierarchical three-dimensional fashion is found to be one of the significant strategies to obtain potential electrode materials for supercapacitors. In addressing this, two diverse kinds of 3D graphene-based hybrid nanomaterials are synthesized using facile and scalable approaches, and then their microstructural properties are studied. The developed 3D nitrogen doped-graphene leaves on bamboo shaped carbon nanotubes (N-glbNT-850) exhibit a high specific capacitance of 528 F/g at a 2 A/g current density. 3D blooming flower structured NiMn2O4-graphene electrode exhibit a high specific capacity and rate capability of 1632 C/g, and 88.1%, respectively. Further, a new ionogel electrolyte film is developed by incorporating a high concentration (96 wt%) of ionic liquid into a 4 wt% polymer host. A flexible symmetric supercapacitor fabricated by using this solid-state ionogel electrolyte film and a flexible asymmetric supercapacitor fashioned of N-glbNT//NiMn2O4-graphene could exhibit a wide working voltage range (3.4 V and 1.6 V, respectively), excellent energy density (96.3 and 156.8 Wh/kg, respectively), outstanding power density (3.39 and 2.34 kW/kg, respectively), and good rate performance with high cycle stability and remarkable flexibility. Thus, the development of inexpensive and efficient electrode materials based on graphene and effective solid-state ionogel electrolytes and the application of these technologies for efficient energy storage devices have all been made possible by the new and effective strategic process, which can be beneficial for commercial applications of energy storage, conversion, and environmental systems.

Numerical modeling of novel cage‐like cross‐linked membranes for enhanced proton conductivity in a high temperature‐polymer electrolyte membrane fuel cell

AbstractPhosphoric acid (PA)‐doped polybenzimidazole (PBI) membranes have encountered several problems associated with high cost, chemical instability, poor solubility in organic solvents, and higher doping level which results in poor mechanical properties and faster degradation of the membrane. Alternative membranes with high proton conductivity and mechanical strength for high‐temperature applications are of great interest, one such membrane being cPBI‐IL X. The cage‐like cross‐linked structure of these membranes shows a dual proton transport path due to which proton conductivity is elevated. The ionic liquid content of these membranes improves the PA absorbing capability and shortens the proton transfer path. These membranes exhibit the highest proton conductivity of 13.3 S/m and better durability compared to existing PBI Membranes. A mathematical model is developed and validated versus published experimental results to account for the proton conductivity of these membranes. The developed model is further investigated for a detailed understanding of polarization phenomena and species distribution.

Selective extraction of molybdenum (VI) with novel ionic liquid from nitric acid solution

ABSTRACT The novel ionic liquid [Aliq–336]+[HCit]− is produced by the reaction of tricaprylylmethyl ammonium chloride, Aliq–336, and tri-sodium citrate. In this investigation, the extraction of Mo(VI) from the nitric acid solution using ([Aliq-336]+[HCit]−) ionic liquid in toluene as a diluent was studied. The effects of various parameters on the extraction process such as shaking time, nitric acid concentration, ionic liquid concentration, hydrogen ion, nitrate ion, Mo(VI) concentration as well as temperature were evaluated. The loading capacity of the prepared ionic liquid was 0.078 mole of Mo(VI) per mole [Aliq-336]+[HCit]−. On the basis of IR spectra and the slope analysis method, the installation of the expected extracted metal species in the organic phase was found to be . As well, the average conditional extraction constant (KCex) for Mo(VI) extraction was 45.96 ± 3.5. The stripping percent of Mo(VI) reached the maximum value (exceeding 99.0%) with 0.5 mol/L sodium acetate as well as 1.0 mol/L of different mineral acids. Based on the obtained results, the prepared ionic liquid in toluene could be used for the effective extraction of molybdenum (VI) from a synthetic mixture of different metal ions found in fission products.

Application of New Ammonium-Based Ionic Liquids for Dehydration of Crude Oil Emulsions

Crude oil emulsions are prevalent in the petroleum industries due to different natural emulsifiers in crude oil. In addition, adding amphiphilic compounds for enhanced oil recovery at high temperatures and pressure under extreme shear stress conditions improved the stability of these emulsions. However, these emulsions are not desirable because they cause different operational problems. Herein, this work aims to synthesize and characterize two novel ionic liquids (ILs) and apply them to the dehydration of water-in-crude oil (W/O) emulsions. For that, tetraethylene glycol (TEG) was reacted with thionyl chloride (TC), yielding dialkyl halide (TEC). After that, TEC was reacted with 4-hexylaniline (HA) or 4-tetradecylaniline (TA) in the presence of sodium carbonate, obtaining the amines TC-HA and TC-TA, respectively. Finally, TC-HA and TC-TA were reacted with acetic acid, yielding the corresponding ionic liquids, THA-IL and TTA-IL. Chemical structure, surface tension (ST), interfacial tension (IFT), thermal stability, and micelle size were investigated using various techniques. The conventional bottle test was used to evaluate the performance of these ILs for dehydration W/O emulsion at different crude oil/brine ratios (ranging from 90/10 to 50/50). The results indicated that the dehydration performance (DP) increased with an increase in IL concentration. In addition, DP improved with increased water contents, reaching 100% for THA-IL and 80% for TTA-IL, respectively, at a crude oil/brine ratio of 50/50. Furthermore, TTA-IL showed higher DP and separated more clear water than THA-IL, which could be linked to its higher ability to reduce IFT due to a longer alkyl chain than THA-IL. The results showed that the synthesized ILs could serve as demulsifiers in the petroleum industry.

Development of an ion gel membrane containing a CO2-philic ionic liquid in interpenetrating semi-crystalline and crosslinkable polymer networks

We developed a tough and highly CO2-permeable ion gel membrane composed of a CO2-philic ionic liquid (IL), 1-ethyl-3-methylimidazolium tetracyanoborate ([Emim][B(CN)4]), and an interpenetrating polymer network (IPN) composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and crosslinkable poly(ethyl acrylate-co-N-succinimide acrylate) (poly(EA-co-NSA)). The semi-crystalline PVDF-HFP and IL-philic poly(EA-co-NSA) networks endowed the ion gel membrane with high mechanical strength and good IL-holding properties. The high mechanical strength and good IL-holding properties achieved by the polymer networks provided the ion gel membrane with high and selective CO2 permeability under pressurized conditions at a trans-membrane pressure difference of 250 kPa. In addition, the high CO2 absorbability of [Emim][B(CN)4] provided the ion gel membrane with a CO2 permeability of more than 2500 barrer and a CO2/N2 permselectivity of approximately 20 at an elevated temperature of 80 °C. It was also demonstrated that the CO2 permeability of the IPN ion gel membrane increased with increasing IL content. The IPN ion gel membrane with an IL content of 85 wt% had a CO2 permeability of 2243 barrer and a CO2/N2 permselectivity of 43 at 30 °C. The excellent CO2 permeability and CO2/N2 permselectivity were not changed by physical aging for more than one week.

Examining the Electrochemical Properties of Hybrid Aqueous/Ionic Liquid Solid Polymer Electrolytes through the Lens of Composition‐Function Relationships

AbstractSolid polymer electrolytes (SPEs) have the potential to meet evolving Li‐ion battery demands, but for these electrolytes to satisfy growing power and energy density requirements, both transport properties and electrochemical stability must be improved. Unfortunately, improvement in one of these properties often comes at the expense of the other. To this end, a “hybrid aqueous/ionic liquid” SPE (HAILSPE) which incorporates triethylsulfonium‐TFSI (S2,2,2) or N‐methyl‐N‐propylpyrrolidinium‐TFSI (Pyr1,3) ionic liquid (IL) alongside H2O and LiTFSI salt to simultaneously improve transport and electrochemical stability is studied. This work focuses on the impact of HAILSPE composition on electrochemical performance. Analysis shows that an increase in LiTFSI content results in decreased ionic mobility, while increasing IL and water content can offset its impact. pfg‐NMR results reveal that preferential lithium‐ion transport is present in HAILSPE systems. Higher IL concentrations are correlated with an increased degree of passivation against H2O reduction. Compared to the Pyr1,3 systems, the S2,2,2 systems exhibit a stronger degree of passivation due to the formation of a multicomponent interphase layer, including LiF, Li2CO3, Li2S, and Li3N. The results herein demonstrate the superior electrochemical stability of the S2,2,2 systems compared to Pyr1,3 and provide a path toward further enhancement of HAILSPE performance via composition optimization.

Are ionic liquids effective curing agents for preparing epoxy adhesives?

This work compares for the first time the efficacy of using different ionic liquids (ILs) as epoxy hardeners in epoxy-based adhesives. Several phosphonium and imidazolium-based ionic liquids were tested as epoxy hardeners, and the thermal and mechanical properties and the lap shear strength of the cured epoxy resins were studied at different IL concentrations. Both the chemical structure and the concentration of ILs were found to impact the final properties of the epoxy resin, but among the ten different ILs studied, three of them cured the epoxy resin effectively and produced similar and even better mechanical properties and lap shear strength than those obtained with traditional amine-based curing agents. These results constitute an important step towards sustainability thanks to the non-volatility of ILs and the significantly lower amount needed for effectively curing epoxy resins.

Separation of polysaccharide and protein by ionic liquid-based extraction techniques

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.

Separation of Palladium from Alkaline Cyanide Solutions through Microemulsion Extraction Using Imidazolium Ionic Liquids.

In this paper, three imidazolium-based ionic liquids, viz., 1-butyl-3-undecyl imidazolium bromide ([BUIm]Br), 1-butyl-3-octyl imidazolium bromide ([BOIm]Br), and 1-butyl-3-hexadecyl imidazolium bromide ([BCIm]Br), were synthesized. Three novel microemulsions systems were constructed and then were used to recover Pd (II) from cyanide media. Key extraction parameters such as the concentration of ionic liquids (ILs), equilibration time, phase ratio (RA/O), and pH were evaluated. The [BUIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion system exhibited a higher extraction percentage of Pd (II) than the [BOIm]Br/n-heptane/n-pentanol/sodium chloride and [BCIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion systems. Under the optimal conditions (equilibrium time of 10 min and pH 10), the extraction percentages of these metals were all higher than 98.5% when using the [BUIm]Br/n-heptane/n-pentanol/sodium chloride microemulsion system. Pd(CN)42- was separated through a two-step stripping procedure, in which Fe (III) and Co (III) were first separated using KCl solution, then Pd(CN)42- was stripped using KSCN solution (separation factors of Pd from Fe and Co exceeded 103). After five extraction-recovery experiments, the recovery of Pd (II) through the microemulsion system remained over 90%. The Pd (II) extraction mechanism of the ionic liquid [BUIm]Br was determined to occur via anion exchange, as shown by spectral analysis (UV, FTIR), Job's method, and DFT calculations. The proposed process has potential applications for the comprehensive treatment of cyanide metallurgical wastewater.

Separation of CO2/N2 mixtures by new IL/Acrylic polymer microcapsules designed by a one-step suspension-based polymerization encapsulation process

In this study, we developed a one-step simplified suspension-based polymerization process for encapsuling ionic liquids (ILs) ([emim][TfO] and [emim][Tf2N]). Acrylic photoreactive monomers were cured using UV-365 light during the encapsulation process forming the capsule shell. The acetone extraction test confirmed IL encapsulation proving a high encapsulation efficiency for all samples (>80 %). For capsules produced with lower IL content, a homogeneous morphology was observed when compared to capsules with higher IL content. Suspension polymerization produced microcapsules presenting polynuclear morphology, as seen in TEM analysis. CO2 sorption ability and CO2/N2 selectivity of the produced capsules were superior when compared to pristine shell material. Capsule stability was proved by submitting the samples to several sorption/desorption cycles. [emim][TfO] microcapsules with low ILs concentration presented superior CO2 sorption results, 53 ± 0.9 mgCO2.g−1 (0.4 Mpa at 45 °C), and CO2/N2 selectivity, 4.5 ± 0.2, compared to [emim][Tf2N] microcapsules. The improvement in sorption capacity of [emim][TfO] microcapsules was greater than 50 % in comparison with the pristine shell material. Electronic structure modeling corroborated the experimental results proving that [emim][TfO] is better to separate CO2/N2 thanks to three electron-rich oxygens. The sorption results allied to the easiness of the process represents a significant contribution to the scientific development of a new, efficient, and simplified method for the encapsulation of ionic liquids, which can be applied in the capture of CO2 in industrial exhaust gas streams.

Recovery of ionic liquids from aqueous solutions using membrane technology

Ionic liquids (ILs) have great potential as solvents and catalysts in the most diverse areas of the chemical industry. However, the need for a process that allows the recycling and purification of ILs in an efficient and economically viable manner is restricting the practical application of these solvents. The recycling processes most used to recover ILs are distillation and evaporation, followed by extraction and crystallization. However, most of these processes demand high energy consumption, or temperatures that may compromise the structural and chemical stability of the ILs. This work focuses on understanding the separation of ionic liquid from aqueous solution using membranes, a technique widely used in industry. The separation of eleven ILs (([C4mim][AOc], [C4mim][SCN], [C4mim][CF3SO3], [C4mim][CF3CO2], [C4mim][Cl], [C8mim][Cl], [P4444][Cl], [N4444][Cl], [C4mpip][Cl], [C4mpyr][Cl] and [C4-2-mpy][Cl]) was studied using a nanofiltration (NF270) and a reverse osmosis (BW30LE) membrane. The influence of cation and anion, pressure, IL concentration, and temperature, on the separation of ILs, was evaluated. The Donnan exclusion mechanism was found to be the limiting factor for the reverse osmosis, while the combination of concentration polarization and sieving mechanism was the limiting factor for nanofiltration membrane. The increase of temperature and pressure leads to an increase in the volumetric flux at the cost of a decrease of the IL retention. On the other hand, the increase in the concentration of the IL solution resulted in an increase in the osmotic pressure and, consequently, a decrease in the volumetric flow and a decrease in the rejection of the IL.

Modulation of Insulin Amyloid Fibrillization in Imidazolium-Based Ionic Liquids with Hofmeister Series Anions.

Amyloid fibrils have immense potential to become the basis of modern biomaterials. The formation of amyloid fibrils in vitro strongly depends on the solvent properties. Ionic liquids (ILs), alternative solvents with tunable properties, have been shown to modulate amyloid fibrillization. In this work, we studied the impact of five ILs with 1-ethyl-3-methylimidazolium cation [EMIM+] and anions of Hofmeisterseries hydrogen sulfate [HSO4-], acetate [AC-], chloride [Cl-], nitrate [NO3-], and tetrafluoroborate [BF4-] on the kinetics of insulin fibrillization and morphology, and the structure of insulin fibrils when applying fluorescence spectroscopy, AFM and ATR-FTIR spectroscopy. We found that the studied ILs were able to speed up the fibrillization process in an anion- and IL-concentration-dependent manner. At an IL concentration of 100 mM, the efficiency of the anions at promoting insulin amyloid fibrillization followed the reverse Hofmeister series, indicating the direct binding of ions with the protein surface. At a concentration of 25 mM, fibrils with different morphologies were formed, yet with similar secondary structure content. Moreover, no correlation with the Hofmeister ranking was detected for kinetics parameters. IL with the kosmotropic strongly hydrated [HSO4-] anion induced the formation of large amyloid fibril clusters, while the other kosmotropic anion [AC-] along with [Cl-] led to the formation of fibrils with similar needle-like morphologies to those formed in the IL-free solvent. The presence of the ILs with the chaotropic anions [NO3-] and [BF4-] resulted in longer laterally associated fibrils. The effect of the selected ILs was driven by a sensitive balance and interplay between specific protein-ion and ion-water interactions and non-specific long-range electrostatic shielding.

TiO2 nanostructures synthesized by electrochemical anodization in green protic ionic liquids for photoelectrochemical applications

This work studies the influence of the 2-hydroxyethylammonium acetate (2-HEAA) ionic liquid (IL) as an electrolyte in the electrochemical anodization of titanium for the synthesis of nanostructures for photoelectrochemical water splitting. Different 2-HEAA IL concentrations were used ranging from 0 to 4% v/v (IL-0 to IL-4) in electrolytes containing NH4F, water and ethylene glycol. Morphological, structural and electrochemical characterization of the nanostructures was carried out by means of field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) analysis. Additionally, photoelectrochemical tests were carried out in order to evaluate the efficiency of these materials as catalysts for water splitting applications. According to the obtained results, the electrolyte used for electrochemical anodization should contain little amount of NH4F (0.05 M) in order to obtain efficient nanostructures for photoelectrochemical purposes. However, small concentrations of IL (IL-0.25) resulted in nanostructures with higher photocurrents than doubling the NH4F concentration to 0.1 M. Therefore, the IL addition contributes to a more sustainable electrolyte formulation. The best photoelectrochemical response for water splitting processes was obtained for the nanostructures anodized with 1% v/v of 2-HEAA IL (IL-1) due to their high surface/area (higher pore diameters, smaller nanotubes wall thickness and higher nanotubes lengths), better crystallinity and electrochemical response, showing photocurrents more than 100% higher than the ones obtained for the nanotubes anodized without IL.