Anion Of Ionic Liquid Research Articles

Influencing the froth flotation of LiAlO2 and melilite solid solution with ionic liquids.

In the present work experiments for single mineral flotation against LiAlO2 and melilite s.s. were carried out for seven ionic liquids (ILs). From these, IL-1 with an imidazolium cation and a bromide anion and IL-7 with a pyridinium cation and a bromide anion were selected for further flotation experiments (dosage, pH). Flotation experiments were also conducted using naphthenic acid, a conventional flotation fatty acid-based collector, and FS-2, a commercial collector in order to compare the results with ILs. Moreover, the effects of different anions in the ILs on the flotation were evaluated and a significant influence on the hardness of anions was found on the flotation process. Finally, a pre-functionalization was also explored with modified cholesterol derivatives, comparing the effect of cholesterylsulfate and cholesterylphosphate on the flotation of LiAlO2 and melilite s.s. This study is vital for the further optimization of lithium recovery from the pyrometallurgical recycling path of lithium-ion batteries and the flotation of primary minerals such as aluminosilicates.

Synergistic Effect of Ionic Liquid (Il) Cation and Anion Inhibits Negative Difference Effect on Mg in Water - Il Mixtures

Synergistic Effect of Ionic Liquid (Il) Cation and Anion Inhibits Negative Difference Effect on Mg in Water - Il Mixtures

Precisely controlled synthesis of Co/N species containing porous carbon for oxygen reduction reaction via anion exchange and CO2 activation

The synthesis strategy of highly dispersed Co/N-doped porous carbon materials using anion exchange resin and ionic liquids.

Coexistence of Tellurium Cations and Anions in Phosphonium-Based Ionic Liquids.

Elemental tellurium readily dissolves in ionic liquids (ILs) based on tetraalkylphosphonium cations even at temperatures below 100 °C. In the case of ILs with acetate, decanoate, or dicyanamide anions, dark red to purple colored solutions form. A study combining NMR, UV‐Vis and Raman spectroscopy revealed the formation of tellurium anions (Ten)2− with chain lengths up to at least n=5, which are in dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an ionic liquid reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. Although the spectroscopic detection of tellurium cations in these solutions is difficult, the coexistence of tellurium cations, such as (Te4)2+ and (Te6)4+, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient to stabilize both types of tellurium ions in solution.

Charge delocalization and hyperpolarizability in ionic liquids

In this work the role that charge delocalization plays in the non-linear optical response of ionic liquids is evaluated. The first hyperpolarizability for the non-linear process of second harmonic generation (SHG) and second hyperpolarizability for the non-linear process of electro-optical Kerr-Effect (EOKE) of a large number of ionic liquid forming ions were estimated by means of density functional theory calculations. The results point to that both charge delocalization and molecular geometry are the key features that govern their hyperpolarizabilities. Our findings show that some of the most commonly used anions in ionic liquids are expected to present strong non-linear responses while common cations present a much more limited performance. However, this limitation can be overcome by a proper tailoring of cations to present charge delocalization over large molecular regions. The hypothesis of additivity of hyperpolarizabilities in ionic liquids is tested and exploited to obtain a map of second and third order non-linear susceptibilities of 1496 ion combinations. This map is intended to be a guide for future works on the hyperpolarizability of ILs.

Overscreening Induced by Ionic Adsorption at the Ionic Liquid/Electrode Interface Detected Using Neutron Reflectometry with a Rational Material Design

Abstract Neutron reflectometry (NR) has been utilized to study the electric double layer (EDL) of ionic liquids (ILs), however, further improvement of the sensitivity toward interfacial structure would be desirable. We recently proposed two ways to improve the NR sensitivity toward the EDL structure at the IL/electrode interface (J. Phys. Chem. C, 123 (2019) 9223). First, as the electrode, a thin film of metal (Nb) was used with the scattering length density (SLD) and thickness controlled to sensitively analyze the potential dependent EDL structure. Second, the IL cation and anion were chosen so that they have large size and large SLD difference, both of which also increase the sensitivity. In the present study, we have further explored this rational material design for the sensitivity enhancement, by changing the film metal from Nb to Bi whose SLD is closer to those for two bulk materials: Si and the IL used, trihexyltetradecylphosphonium bis(nonafluorobutanesulfonyl)amide. We successfully observed not only the first ionic layer in the EDL but also the overlayers, revealing that the IL cation is specifically adsorbed on the electrode and that the cation-rich first layer induces overscreening in the overlayers up to the third ionic layer.

Physico-Chemical Characterization of Binary and Ternary Mixtures of Imidazolium Based Cation and Common Anion Ionic Liquids with Lactams

Physico-Chemical Characterization of Binary and Ternary Mixtures of Imidazolium Based Cation and Common Anion Ionic Liquids with Lactams

Performances of different DFT functionals to calculate the anodic limit of fluorinated sulphonyl-imide anions for lithium cells

In this paper we investigated the calculation of the anodic limit of two anions of ionic liquids, largely used as electrolyte of lithium batteries. Starting from a model based on calculations performed on single ions at the MP2 level of theory, we showed that the matching between calculation and experiments decreases while using more expanded basis set with respect to 6-31G**, possibly because of the destabilization of the neutral species when larger basis sets are considered. Additionally, in order to decrease the computational time, the performances for the calculation of the anodic limit obtained by means of a series of DFT functionals with increasing level of complexity (from the Generalized Gradient Approximation to the Range Separated Hybrid meta-Generalized Gradient Approximation) were compared. Overall, the best performing functionals are BMK, ωB97M-V and MN12-SX, while acceptable results can be obtained by M06-2X, M11, M08-HX and M11-L. Some less computationally expensive functionals, like CAM-B3LYP and ωB97X-D, also provide reasonable values of the anodic limit.

Evaluation of the efficiency of ionic liquids in the demulsification of oil-in-water emulsions

The production of oil in water emulsions (O/W-EMUL) is prevalent in the petroleum sector due to the presence of several stabilizers; however, O/W-EMUL is an unwanted phenomenon. Given that, this study evaluates the efficiency of three ionic liquids (ILs), two halogenide ILs (HILs-1, HILs-2), and one is non-halogenide IL (Non-HIL) as demulsifiers for the recovery of oil from O/W-EMUL at a concentration of 500 mg/L. The percentage demulsification efficiency (D%) (i.e., the percentage of oil removed from the O/W-EMUL) was examined using tube and bottle tests. The results of the bottle tests demonstrated that the halogenide ionic liquids (HILs) could achieve a higher D% in comparison to the Non-HIL. The D% achieved within 20 min of treatment with HILs-1, HILs-2, and Non-HIL was found to be ∼97.7%, 88.2%, and 85.2%, respectively. Increasing the volume of ILs (VILs), which are normally recycled, can help overcome the surfactant’s effect to achieve a D% > 95%. The demulsification mechanism is based on ion exchange between the anionic part of the ILs and the oil–surfactant interphase. Recycling the ILs can be enhanced by reestablishing the IL anion part using water-free inversed ion exchange mixed with salts. The results suggest that ILs can be an appropriate substitute for commercial demulsifiers. Though, further efforts are needed to produce non-toxic and cost-effective ILs with low viscosity. The efficiency of the demulsification process may be further enhanced when using ILs with other separation processes. The achieved results support upcoming research works that apply ILs for oil removal from O/W-EMUL.

Understanding the Failure Mechanism of Rechargeable Aluminum Batteries: Metal Anode Perspective Through X‐Ray Tomography

Rechargeable aluminum batteries (AlBs), which represent cost‐effective energy‐storage devices due to the abundance of natural aluminum resources, have emerged as promising candidates for the next generation of rechargeable batteries. Although the electrochemical deposition of aluminum in ionic liquids (ILs) is well investigated for aluminum refining, the reversible electrochemical deposition/dissolution behavior of aluminum ions is not trivial. More specifically, the dendrite growth issue, which is common in Li metal anodes, is scarcer or vague. Herein, the electrochemical stability of the aluminum metal anode in IL electrolytes is investigated and the failure mechanism is discussed. It is confirmed that the inorganic anion of ILs mainly affects the electrochemical stability, whereas the organic cation influences the aluminum metal degradation. X‐ray computed tomography results further identify deterioration of the surface morphology of the aluminum metal. The formation of “dead aluminum” is further confirmed, which indeed causes cell failure with repeated cycles. Finally, using the predeposited aluminum graphene paper as an alternative anode candidate for AlBs is further demonstrated.

Energetics of Li+ Coordination with Asymmetric Anions in Ionic Liquids by Density Functional Theory

The energetics, coordination, and Raman vibrations of Li solvates in ionic liquid (IL) electrolytes are studied with density functional theory (DFT). Li+ coordination with asymmetric anions of cyano(trifluoromethanesulfonyl)imide ([CTFSI]) and (fluorosulfonyl)(trifluoro-methanesulfonyl)imide ([FTFSI]) is examined in contrast to their symmetric analogs of bis(trifluoromethanesulfonyl)imide ([TFSI]), bis(fluorosulfonyl)imide ([FSI]), and dicyanamide ([DCA]). The dissociation energies that can be used to describe the solvation strength of Li+ are calculated on the basis of the energetics of the individual components and the Li solvate. The calculated dissociation energies are found to be similar for Li+-[FTFSI], Li+-[TFSI], and Li+-[FSI] where only Li+-O coordination exists. Increase in asymmetry and anion size by fluorination on one side of the [TFSI] anion does not result in significant differences in the dissociation energies. On the other hand, with [CTFSI], both Li+-O and Li+-N coordination are present, and the Li solvate has smaller dissociation energy than the solvation by [DCA] alone, [TFSI] alone, or a 1:1 mixture of [DCA]/[TFSI] anions. This finding suggests that the Li+ solvation can be weakened by asymmetric anions that promote competing coordination environments through enthalpic effects. Among the possible Li solvates of (Li[CTFSI]n)−(n−1), where n = 1, 2, 3, or 4, (Li[CTFSI]2)−1 is found to be the most stable with both monodentate and bidentate bonding possibilities. Based on this study, we hypothesize that the partial solvation and weakened solvation energetics by asymmetric anions may increase structural heterogeneity and fluctuations in Li solvates in IL electrolytes. These effects may further promote the Li+ hopping transport mechanism in concentrated and multicomponent IL electrolytes that is relevant to Li-ion batteries.

Enhancing the Thermal Stability of Ionogels: Synthesis and Properties of Triple Ionic Liquid/Halloysite/MCC Ionogels.

In this study, an ionic liquid (IL), 1-butyl-3-methylimidazolium acetate, was used to prepare ionogels with microcrystalline cellulose (MCC) and halloysite (Hal). SEM, XRD, TG, DSC, FTIR spectroscopy, conductometry and mechanical tests were used to study the morphology, structure, thermal behaviour and electrophysical and mechanical characteristics of synthesised ionogels. XRD analysis showed a slight decrease in the interlayer space of halloysite in ionogels containing MCC, which may have been associated with the removal of residual water molecules resulting from hydrophilic IL anions and polymer macromolecules. A change in conductivity and glass-transition temperature of the ionic liquid was revealed due to intercalation into halloysite (a confinement effect) and modification with cellulose. For triple IL/Hal/MCC ionogels, the characteristic thermal degradation temperatures were higher than the corresponding values for IL/Hal composites. This indicates that the synthesised IL/Hal/MCC ionogels are characterised by a greater thermal stability than those of IL/Hal systems.

Comprehensive Interrogation on Acetylcholinesterase Inhibition by Ionic Liquids Using Machine Learning and Molecular Modeling.

Quantitative structure-activity relationship (QSAR) modeling can be used to predict the toxicity of ionic liquids (ILs), but most QSAR models have been constructed by arbitrarily selecting one machine learning method and ignored the overall interactions between ILs and biological systems, such as proteins. In order to obtain more reliable and interpretable QSAR models and reveal the related molecular mechanism, we performed a systematic analysis of acetylcholinesterase (AChE) inhibition by 153 ILs using machine learning and molecular modeling. Our results showed that more reliable and stable QSAR models (R2 > 0.85 for both cross-validation and external validation) were obtained by combining the results from multiple machine learning approaches. In addition, molecular docking results revealed that the cations and organic anions of ILs bound to specific amino acid residues of AChE through noncovalent interactions such as π interactions and hydrogen bonds. The calculation results of binding free energy showed that an electrostatic interaction (ΔEele < -285 kJ/mol) was the main driving force for the binding of ILs to AChE. The overall findings from this investigation demonstrate that a systematic approach is much more convincing. Future research in this direction will help design the next generation of biosafe ILs.

Charge-driven interaction for adsorptive removal of organic dyes using ionic liquid-modified graphene oxide

A facile approach is presented to synthesize the ionic liquid-grafted graphene oxide (GO-ImOH) for fast and efficient adsorptive removal of cationic dyes. A coupling reaction between the hydroxyl terminal of imidazolium ionic liquid and the carboxylic group of GO, yielded the GO-ImOH hybrid material. The higher surface negative charge (−32 mV) and excellent dispersibility make the GO-ImOH an efficient adsorbent for cationic dyes. The GO-ImOH showed excellent removal efficiency for methylene blue (cationic dye), whereas it could adsorb only 22% methyl orange (anionic dye). The GO-ImOH displayed significantly higher adsorptive removal capacity for cationic dye compared to that of GO adsorbent. The chemical and structural features of GO-ImOH and spectroscopic analyses (FTIR and Raman) of pristine and recovered GO-ImOH adsorbent suggested multiple adsorptive interaction pathways (electrostatic, π-cation, π-π interactions, and hydrogen linkages) between the GO-ImOH adsorbent and the dye molecules. The work paves a new direction for the development of ionic liquids-modified 2D nanomaterials for efficient and fast adsorptive removal of organic pollutants, where the adsorptive sites on the surface of 2D nanomaterials can be tuned by selecting the desired functionalities from a diversified library of cations and anions of ionic liquids.

Structure and properties of the (α-PicH)3[RhCl6] salt containing 2-methylpyridinium cations

The organic-inorganic hybrid salt consisting of 2-methylpyridinium cation (α-picoline, α-Pic) and hexachlororhodate(III) anion (α-PicH)3[RhCl6] was prepared in high yield. The compound was characterized using a variety of spectral techniques (UV–Vis, IR, Raman, XAFS) and its crystal structure was determined by X-ray single crystal diffraction. The system of strong NH…Cl hydrogen bonds is observed in the structure between organic cations and complex anions resulting in the formation of oppositely charged conglomerates {(α-PicH)4[RhCl6]}+ and {(α-PicH)2[RhCl6]}−. The chemical processes taking place during the thermal decomposition of the salt in He and H2/He atmospheres were studied, and the products of these transformations were identified. The unique thermal stability of [RhCl6]3− anions in an α-PicHCl ionic liquid and a range of temperature up to 250 °C was demonstrated using UV–Vis absorption spectroscopy.

The synthesis and application of poly(ionic liquid)s functional materials

Poly(ionic liquid)s are ionic polymers containing ionic liquid anion and cation structures in polymer repeating units. Poly(ionic liquid)s possess the physical and chemical properties of small ionic liquid molecules (structural diversity, adjustable solubility, chemical/thermal stability, conductivity, etc .) and the mechanical properties and processability of polymers, which makes it possible to apply in conductive materials, intelligent response materials, biomedical materials and other fields. This article mainly reviews the synthesis methods of poly(ionic liquid)s and their potential applications as functional materials in the fields of energy devices, smart response devices and antibacterial materials.

Exploring the solvation behavior of guanidinium based carboxylate ionic liquids in DMSO and DMF through apparent molar properties

The solvation behavior of 1,1,3,3 tetramethylguanidinium [TMG] ionic liquids (ILs) containing different carboxylate anions, octanoate (C8H15O2)-, decanoate (C10H19O2)- and laurate (C12H23O2)-, in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) are examined through apparent molar properties. In this work, three ILs were chosen as they are protic and interact with polar solvents, affecting the thermophysical properties. We have measured the thermophysical properties to study the interactions between ion-ion and ion–solvent and analyzed the influence of IL anion and temperature through the experimental measurements of density and speed of sound. The measurement was carried out as a function of molality (0.05–1.0 mol∙kg−1) and temperature from 293.15 to 328.15 K under atmospheric pressure. The binary systems contained the ILs [TMGH]+[C8H15O2]-, [TMGH]+[C10H19O2]- and [TMGH]+[C12H23O2]-. The apparent molar volume (Vϕ) and the apparent molar isentropic compressibility (Ks,∅)were calculated using the experimental data and a Redlich-Mayer type equation was fitted to calculate the limiting parameters (V∅∞ and Ks,∅∞)to understand the vital empirical parameters of the studied ILs. The effect of carbon chain length on apparent molar volume (Vϕ) and the apparent molar isentropic compressibility (Ks,∅) with concentration and temperature range was studied.

The quantitative structure-property relationships for the gas-ionic liquid partition coefficient of a large variety of organic compounds in three ionic liquids

Ionic liquids (ILs) have unique properties as solvents and electrolytes, which need to be studied using innovative machine learning (ML) approaches and which allow the identification of a chemical environment that can be adapted to different applications. The gas-ionic liquid partition coefficients of organic compounds is one such application-oriented parameter for selecting both ionic liquids and organic compounds as quickly, cost-effectively, and as accurately as possible. Therefore, multiple linear regression (MLR) and random forest (RF) quantitative structure–property relationships (QSPRs) were developed for predicting the gas-ionic liquid partition coefficient (log K) of structurally variable organic solutes in the ionic liquids N-butyl-N-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([BMPyrr]+[FAP]−), N-butyl-N-methylpyrrolidinium tricyanomethanide ([BMPyrr]+[C(CN)3]−) and 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([MeoeMPyrr]+[FAP]−). All derived models have excellent prediction capability evidenced by high 5-fold cross-validated coefficients of determination in the range 0.88 – 0.94, complemented with other high statistical parameters. Compared to the MLR approach, the non-linear RF models statistics improved in two of three data series. Analysis of the molecular descriptors selected into MLR models revealed major solvent–solute interactions, with primary contributions from Coulomb and dipolar or hydrogen bonding interactions and followed by the descriptors that expose dispersion force related interactions. Relations to all the aforementioned solvent–solute interactions were also found in RF models descriptor interpretation. Comparison of models demonstrated that a common anion in different ILs produces a significant correlation between the data series log K values, while that of ILs with a common cation are less but still significantly correlated. The lower correlation could be attributed to varying structural differences in the corresponding ions, or the anion might have a more substantial role in determining partition properties with the organic solutes in the series.

Effect of Bulky Anion around the Dication on the Electronic Structure and Normal Frequencies in 1,3-Bis(3-methylimidazolium-1-yl)propane Bis(trifluoromethanesulfonyl)imide Ionic Liquid.

A manifestation of hydrogen bonding between the dication and anions attributed to their relative position of the anions around the cation can influence both the conformational equilibrium and the physical properties of ionic liquids. With this view, we studied the electronic structure and normal frequencies using density functional theory calculations to analyze the hydrogen-bonding interactions in dicationic ionic liquids. The conformers are distinguished based on the hydrogen-bonding sites of the cation and anion. The weak hydrogen bonding between the dication and anions in dication ionic liquids can lead to greater conformational equilibrium compared to the monocation system. Consequences of these interactions for the vibrational spectrum are analyzed to provide an insight into the conformational equilibrium in dicationic ionic liquids at the molecular level.

The Activity Enhancement Effect of Ionic Liquids on Oxygen Reduction Reaction Catalysts: From Rotating Disk Electrode to Membrane Electrode Assembly

Ionic liquids (ILs) have been explored as a surface modification strategy to promote the oxygen reduction reaction (ORR) on Pt/C and their chemical structures were identified to have strong influence on the ORR activities. To better understand the roles of anion and cation of ILs on the catalytic reaction, two cations ([MTBD]+ and [bmim]+) were paired with three anions ([TFSI]−, [beti]−, and [C4F9SO3]−) to form various IL structures. By systematically varying the IL combinations and studying their effects on the electrochemical behaviors, such as electrochemical surface area and specific ORR activities, it was found that cation structure had a higher influence than anion, and the impact of the [MTBD]+ series was stronger than the [bmim]+ series. In addition to the investigation in the half-cell, studies were also extended to the membrane electrode assembly (MEA). Considerable performance enhancements were demonstrated in both the kinetic region and high current density region with the aid of IL. This work suggests that IL modification can provide a complementary approach to improve the performance of proton exchange membrane fuel cells.