Alkyl Chain Length Of Cation Research Articles

Protic Ionic Liquid Cation Alkyl Chain Length Effect on Lysozyme Structure.

Solvents that stabilize protein structures can improve and expand their biochemical applications, particularly with the growing interest in biocatalytic-based processes. Aiming to select novel solvents for protein stabilization, we explored the effect of alkylammonium nitrate protic ionic liquids (PILs)-water mixtures with increasing cation alkyl chain length on lysozyme conformational stability. Four PILs were studied, that is, ethylammonium nitrate (EAN), butylammonium nitrate (BAN), hexylammonium nitrate (HAN), and octylammonium nitrate (OAN). The surface tension, viscosity, and density of PIL-water mixtures at low to high concentrations were firstly determined, which showed that an increasing cation alkyl chain length caused a decrease in the surface tension and density as well as an increase in viscosity for all PIL solutions. Small-angle X-ray scattering (SAXS) was used to investigate the liquid nanostructure of the PIL solutions, as well as the overall size, conformational flexibility and changes to lysozyme structure. The concentrated PILs with longer alkyl chain lengths, i.e., over 10 mol% butyl-, 5 mol% hexyl- and 1 mol% octylammonium cations, possessed liquid nanostructures. This detrimentally interfered with solvent subtraction, and the more structured PIL solutions prevented quantitative SAXS analysis of lysozyme structure. The radius of gyration (Rg) of lysozyme in the less structured aqueous PIL solutions showed little change with up to 10 mol% of PIL. Kratky plots, SREFLEX models, and FTIR data showed that the protein conformation was maintained at a low PIL concentration of 1 mol% and lower when compared with the buffer solution. However, 50 mol% EAN and 5 mol% HAN significantly increased the Rg of lysozyme, indicating unfolding and aggregation of lysozyme. The hydrophobic interaction and liquid nanostructure resulting from the increased cation alkyl chain length in HAN likely becomes critical. The impact of HAN and OAN, particularly at high concentrations, on lysozyme structure was further revealed by FTIR. This work highlights the negative effect of a long alkyl chain length and high concentration of PILs on lysozyme structural stability.

Imidazolium-based ionic liquids with increasing alkyl chain length of cations decrease the stability and fibrillation propensity of lysozyme

Imidazolium ionic liquids with longer alkyl side chains show a larger destabilization effect on lysozyme. Increased hydrophobicity of the IL increases its binding affinity and inhibits the fibril formation of lysozyme.

Solubility of carbon dioxide in some imidazolium and pyridinium-based ionic liquids and correlation with NRTL model

In this study, the solubility of carbon dioxide gas in a series of 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids with various anions, viz. thiocyanate ([SCN]−), chloride ([Cl]−) and bromide ([Br]−) was investigated using a quartz crystal microbalance at 298.15 K and pressures up to 0.4 MPa. CO2 solubility in the ionic liquids correlates well with the non-random two-liquid (NRTL) model. The results indicate that the cation alkyl chain length and the type of anion have the main effects on the solubility of carbon dioxide in ionic liquids. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased with increasing alkyl chain length of the cation. Also, CO2 solubility was strongly dependent on the selection of the anion. CO2 solubility in both 1-alkyl-4-methyl pyridinium and 1-alkyl-3-methylimidazolium-based ionic liquids increased as follows: [SCN]− > [Cl]− > [Br]−.

The impact of the cation alkyl chain length on the wettability of alkylimidazolium-based ionic liquids at the nanoscale.

Ionic liquids (ILs) have been widely used for energy storage and conversion devices due to their negligible vapor pressure, high thermal stability, and outstanding interfacial properties. Notably, the interfacial nanostructure and the wettability of thin ionic liquid films on solid surfaces are of utmost relevance in nanosurface science and technology. Herein, a reproducible physical vapor deposition methodology was used to fabricate thin films of four alkylimidazolium bis(trifluoromethylsulfonyl)imide ILs. The effect of the cation alkyl chain length on the wettability of ILs was explored on different surfaces: gold (Au); silver (Ag); indium-tin oxide (ITO). High-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to evaluate the morphology of the produced micro- and nanodroplets and films. SEM and AFM results revealed an island growth for all the ILs deposited on ITO and Ag surfaces, with a lower minimum free area to promote nucleation (MFAN) in Ag and higher wettability for ILs having larger non-polar domains. The low wettability of ITO by the studied ILs was highlighted. For long-chain ILs, nucleation and growth mechanisms were strongly conditioned by coalescence processes. The results also supported the higher affinity of the ILs to the Au surface. The increase in the length of the cation alkyl chain was found to promote a better film adhesion inducing a 2D growth and higher wetting ability.

Phosphonium-based ionic liquids as antifungal agents for conservation of heritage sandstone.

With a view to preventing fungal deterioration of historical stone artworks, we report the use of phosphonium-based ionic liquids (ILs) as potent antifungal agents against dematiaceous fungi commonly found on heritage stones. Three ILs: tributyldodecylphosphonium polyoxometalate [P44412][POM], tributyltetradecylphosphonium polyoxometalate [P44414][POM], and trihexyltetradecylphosphonium polyoxometalate [P66614][POM] were prepared and their thermal stabilities and in vitro antifungal activities were evaluated. From the ramped temperature thermogravimetric analysis and antifungal experiments it can be clearly observed that the alkyl chain length of the tetraalkylphosponium cation has a significant influence on the thermal and antifungal properties. The thermal stability and antifungal activity decreased as the number of carbon atoms of the alkyl substituents increased and, thus, followed the order [P44412][POM] > [P44414][POM] > [P66614][POM]. In addition, inoculation of four fungal species on IL-coated sandstone surfaces showed significant inhibition of fungal growth, endowing the materials with potential applications in heritage sandstone conservation.

(Invited) Enhancement of the ORR Activity By Hydrophobic Species Analyzed Using Single Crystal Electrodes

Introduction Enhancement of the oxygen reduction reaction (ORR) is important for the development of fuel cells. Pt oxides are blocking species of the ORR on Pt electrodes.1,2 Theoretical calculation predicts that the change of adsorbed water structure inhibits the formation of Pt oxides on n(111)−(111) series of Pt, resulting in the high ORR activity of this series.3 In the notation of high index planes n(hkl)−(mno), n, (hkl) and (mno) show the number of terrace atomic rows, structures of terrace and step, respectively.Hydrophobic species also changes water structure around electrode surfaces. Modification with alkyl amines (OA/PA) and melamine enhances the ORR activity of Pt nanoparticles.4,5 This paper summarized the structural effects on the enhancement of the ORR by hydrophobic species on single crystal electrodes of Pt6 and Pt x Pd y Co z . Experimental Linear sweep voltammograms were measured using rotating disk electrode (RDE) in 0.1 M HClO4 saturated with O2. Potential was scanned positively from 0.05 V(RHE) at scanning rate of 0.010 V s−1. The ORR activity was estimated using the specific activity at 0.90 V(RHE). Hydrophobic species examined were alkyl amines (OA/PA), tetraalkyl ammonium cation (THA+) and melamine. The structure formulae and the hard sphere models of single crystal electrodes are shown in Fig. 1. Results and Discussion <Pt single crystal electrodes> Alkyl amines (OA/PA) enhance the ORR activity on n(111)-(111) series of Pt with 7 ≤ n.7 This fact indicates that wide (111) terrace (7 ≤ n) is necessary for the ORR activation by OA/PA. The ORR activity on flat Pt(111) is most activated by OA/PA. However, OA/PA markedly deactivates the ORR on flat Pt(100). Wide flat hexagonal terrace plays a key role in the activation by OA/PA. Modification with OA/PA decreases the charges of Pt oxide formation of voltammograms of all the single crystal electrodes, even on the surfaces of which ORR activity decreases after the modification. Infrared reflection absorption spectroscopy (IRAS) shows that the formation of ice-like water with smaller cluster size enhances the ORR activity after OA/PA modification.8 The ORR activity of Pt(111) is enhanced with the increase of the alkyl chain length of tetraalkyl ammonium cation. The ORR activity of Pt(111) modified with THA+ is 8 times as high as that of bare Pt(111).9 IRAS band intensity of PtOH decreases markedly after THA+ modification. This fact indicates that the ORR activity of Pt(111) is extremely high without Pt oxides. THA+ slightly enhanced the activity of Pt(331) = 3(111)-(111) that has the highest ORR activity in single crystal Pt electrodes. Melamine enhances the ORR activity on all the n(111)-(111) series of Pt.10 The activity on Pt(111) is enhanced most markedly again after melamine modification. Melamine also increases the activity of Pt(331) twice, giving the highest activity in the Pt single crystal electrodes examined. IRAS spectra show that the enhancement of the activity was attributed to the decrease of the coverage of PtOH. <Pt x Pd y Co z single crystal electrodes> Pt x Pd y Co z single crystal electrodes have higher ORR activity than Pt and Pt3Co single crystal electrodes.11 THA+ enhances the ORR activity of Pt x Pd y Co z (111) electrodes. The ORR activity of PtPd0.1Co0.2(111) modified with THA+ is 3.7 and 19 times as high as that of bare PtPd0.1Co0.2(111) and Pt(111), respectively. However, THA+ deactivates the ORR on Pt x Pd y Co z (100) and Pt x Pd y Co z (110) electrodes. Melamine increases the ORR activity of all the Pt x Pd y Co z single crystal electrodes. The enhancement ratio of PtPd0.1Co0.2(111) (2.1) is the highest in Pt x Pd y Co z single crystal electrodes examined. Acknowledgements This study was supported by New Energy and Industrial Technology Development Organization (NEDO). References N. M. Marković, H. A. Gasteiger, B. N. Grgur, and P. N. Ross, J. Electroanal. Chem., 467, 157 (1999). T. Ueno, H. Tanaka, S. Sugawara, K. Shinohara, A. Ohma, N. Hoshi, and M. Nakamura, J. Electroanal. Chem., 800, 162 (2017). R. Jinnouchi, K. Kodama, and Y. Moromoto, J. Electroanal. Chem., 716, 31 (2014).K. Miyabayashi, H. Nishihara, and M. Miyake, Langmuir, 30, 2936 (2014). M. Asahi, S. Yamazaki, N. Taguchi, and T. Ioroi, J. Electrochem. Soc., 166, F498 (2019). N. Hoshi, and M. Nakamura, Chem. Lett., 50, 72 (2021). K. Saikawa, M. Nakamura, and N. Hoshi, Electrochem. Commun., 87, 5 (2018). N. Hoshi, K. Saikawa, and M. Nakamura, Electrochem. Cummun., 106, 106536 (2019). T. Kumeda, H. Tajiri, O. Sakata, N. Hoshi, and M. Nakamura, Nat. Commun., 9, 4378 (2018). N. Wada, M. Nakamura, and N. Hoshi, Electrocatalysis, 11, 275 (2020). M. Torihata, M. Nakamura, N. Todoroki, T. Wadayama, and N. Hoshi, Electrochem. Commun., 125, 107007 (2021). Figure 1

Dissolution of Cellulose in Ionic Liquid-DMSO Mixtures: Roles of DMSO/IL Ratio and the Cation Alkyl Chain Length.

The dissolution behavior of cellulose in the mixtures of dimethyl sulfoxide (DMSO) and different ionic liquids (ILs) at 25 °C was studied. High solubility of cellulose was reached in the mixtures of ILs and DMSO at mole fractions of 1:2, 1:2, and 1:1 for 1-butyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, and 1-ethyl-3-methylimidazolium acetate, respectively. At high DMSO/IL molar ratios (10:1–2:1), a longer alkyl chain of the IL cation led to higher cellulose solubility. However, shorter cation alkyl chains favored cellulose dissolution at 1:1. Rheological, Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements were used to understand cellulose dissolution. It was found out that the increase of the DMSO ratio in binary mixtures caused higher cellulose solubility by decreasing the viscosity of systems. For cations with longer alkyl chains, stronger interaction between the IL and cellulose and higher viscosity of DMSO/IL mixtures were observed. The new knowledge obtained here could be useful to the development of cost-effective solvent systems for biopolymers.

Experimental and DFT studies on foam performances of lauryl ether sulfate-based anionic surface active ionic liquids

Three lauryl ether sulfate-based anionic surface active ionic liquids (SAILs), 1-butyl-3-methylimidazolium lauryl ether sulfate ([Bmim][C12H25O(C2H4O)2SO3]), 1-hexyl-3-methylimidazolium lauryl ether sulfate ([Hmim][C12H25O(C2H4O)2SO3]), and 1-octyl-3-methylimidazolium lauryl ether sulfate ([Omim][C12H25O(C2H4O)2SO3]) were synthesized. Physicochemical properties (surface properties, micellization, adsorption, and aggregation parameters) of three anionic SAILs and sodium lauryl ether sulfate (SLES) were determined. The critical micelle concentration (CMC) values of [Bmim][C12H25O(C2H4O)2SO3], [Hmim][C12H25O(C2H4O)2SO3], and [Hmim][C12H25O(C2H4O)2SO3] (from surface tension) were 0.569 mmol/L, 0.361 mmol/L, and 0.190 mmol/L, respectively. Micellization of three SAILs were spontaneous, endothermic, and entropy-driven. Foaming performances (foaming ability, foam stability, and foam composite index) of three anionic SAILs and SLES were determined using Ross-Miles methods. The foaming abilities of three SAILs followed: [Hmim][C12H25O(C2H4O)2SO3] > [Bmim][C12H25O(C2H4O)2SO3] > [Omim][C12H25O(C2H4O)2SO3]. While the foam stabilities and foam composite index (FCI) of three SAILs followed: [Omim][C12H25O(C2H4O)2SO3] > [Hmim][C12H25O(C2H4O)2SO3] > [Bmim][C12H25O(C2H4O)2SO3]. The structure effect of SAILs on foam performances were analyzed using density functional theory (DFT) calculations. Binding energy values of three SAIL hydrates followed the trend: [Omim][C12H25O(C2H4O)2SO3](H2O)n > [Hmim][C12H25O(C2H4O)2SO3](H2O)n > [Bmim][C12H25O(C2H4O)2SO3](H2O)n. DFT results showed the increase of alkyl chain length of imidazolium cation was beneficial for the stability of SAIL hydrates, which resulted in higher foam performances. The information will shed light on screening of novel SAILs for surfactant foam enhanced oil recovery (EOR).

Effect of alkyl chain length of imidazolium cations on foam properties of anionic surface active ionic liquids: Experimental and DFT studies

Two anionic surface active ionic liquids (SAILs), 1-hexyl-3-methylimidazolium dodecyl sulfate ([Hmim][C12H25SO4]) and 1-octyl-3-methylimidazolium dodecyl sulfate ([Omim][C12H25SO4]) were synthesized using imidazolium ionic liquids (ILs) and sodium dodecyl sulfate (SDS). The critical micelle concentration (CMC) values, thermodynamic properties, and aggregation parameters were determined using surface tension measurements, steady state fluorescence tests, and electrical conductivity measurements. CMC values (from surface tension) of [Hmim][C12H25SO4] and [Omim][C12H25SO4] were 1.075 mmol/L and 0.278 mmol/L, respectively. The micellization process of [Omim][C12H25SO4] and [Hmim][C12H25SO4] was spontaneous, endothermic, and entropy-driven. Foaming performances (foaming ability, foam stability, and foam composite index) of three SAILs ([Bmim][C12H25SO4], [Hmim][C12H25SO4], and [Omim][C12H25SO4]) were determined using Ross-Miles methods. The foaming abilities of SAILs followed the order: [Hmim][C12H25SO4] > [Bmim][C12H25SO4] > [Omim][C12H25SO4]. While the foam stabilities and foam composite index (FCI) of SAILs followed the order: [Omim][C12H25SO4] > [Hmim][C12H25SO4] > [Bmim][C12H25SO4]. The structure effect of three SAILs ([Bmim][C12H25SO4], [Hmim][C12H25SO4], and [Omim][C12H25SO4]) on foam performances were analyzed by density functional theory (DFT) calculations. Binding energy of three SAIL hydrates followed the trend: [Omim][C12H25SO4](H2O)n > [Hmim][C12H25SO4](H2O)n > [Bmim][C12H25SO4](H2O)n. DFT results showed the increase of alkyl chain length of imidazolium cation was beneficial to the stability of SAIL hydrates, which resulted in higher foam performances. The information will shed light on rapid screening of novel surface active ionic liquids for surfactant foam enhanced remediation (SFER).

Imidazolium Triflate Ionic Liquids' Capacitance-Potential Relationships and Transport Properties Affected by Cation Chain Lengths.

In this paper we report the effects of five imidazolium cations with varying alkyl chain lengths to study the effects of cation size on capacitance versus voltage behavior. The cations include ethyl-, butyl-, hexyl-, octyl-, and decyl-3-methylimidazolium, all paired with a triflate anion. We analyze the capacitance with respect to the cation alkyl chain length qualitatively and quantitatively by analyzing changes in the capacitance-potential curvature shape and magnitude across several standard scanning protocols and electrochemical techniques. Further, three transport properties (viscosity, diffusion coefficient, and electrical conductivity) are experimentally determined and integrated into the outcomes. Ultimately, we find higher viscosities, lower diffusion coefficients, and lower electrical conductivities when the alkyl chain length is increased. Also, capacitance values increase with cation size, except 1-octyl-3-methylimidazolium, which does not follow an otherwise linear trend. This capacitive increase is most pronounced when sweeping the potential in the cathodic direction. These findings challenge the conventional hypothesis that increasing the length of the alkyl chain of imidazolium cations diminishes the capacitance and ionic liquid performance in charge storage.

New reactive ionic liquids as carriers in polymer inclusion membranes for transport and separation of Cd(II), Cu(II), Pb(II), and Zn(II) ions from chloride aqueous solutions

Three new reactive ionic liquids (RILs) based on the imidazole derivatives were synthesized and used as carriers in polymer inclusion membranes (PIMs) composed of cellulose triacetate (CTA) as a polymer matrix and o–nitrophenyl octyl ether (NPOE) as a plasticizer. The effect of alkyl chain length (C1, C4, and C8) in the imidazolium cation of RILs on the transport and separation properties was evaluated. From among three synthesized RILs only the RIL with the longest alkyl chain (RILC8_Br) can be successfully applied as the carrier for Cd(II) removal from multicomponent aqueous chloride solution containing also Cu(II), Pb(II), and Zn(II) ions. The effects of the stripping phase composition, HCl concentration in the feed solution, and the carrier content in the membrane on the separation performance and transport effectiveness were studied. The results indicate that the RILC8_Br ionic liquid enables selective transport of Cd(II) ions and their active concentration in the stripping solution with the fluxes reaching a value of 2.7 × 10−10 mol/cm2s. In the investigated feed solution concentration range, the selectivity order was found to be Cd(II) > Zn(II) > Pb(II) ≫ Cu(II) and it was independent of the experimental conditions. For a description of the transport kinetics a model similar to the first-order reversible reaction equations was applied and its applicability was proved.

Molecular dynamics simulation of extractive desulfurization of diesel oil model using magnetic ionic liquids

This paper serves as a molecular dynamics (MD) study on the desulfurization of diesel oil model using magnetic ionic liquids (MILs). In this regard, three different MILs, namely, [emim][FeCl4], [bmim][FeCl4] and [hmim][FeCl4] have been used to remove the dibenzothiophene (DBT) from n-dodecane as diesel oil model. The effects of alkyl chain length of cation in MIL, temperature, initial sulfur content and mass ratio of MIL to diesel oil on two vital parameters of desulfurization process i.e. percentage of S-removal and Nernst partition coefficient (KN) were investigated. These two parameters were calculated based on the method proposed by Feng and Mi (Ind. Eng. Chem. Res. 2014, 53, 20234-20240), in which they used the radial distribution function (RDF) plots obtained by Conductor-like Screening Model for Real Solvents (COSMO-RS) to evaluate the desulfurization of fuel oil, quantitatively. Our results showed that the [bmim][FeCl4] has the highest DBT-philisity and its S-removal efficiency increases with increasing temperature and the concentration of the MIL. Furthermore, from the investigation of the initial sulfur content in diesel oil model it is concluded that the MIL can be a good extractor for oil refinery applications with a wide range of sulfur content in diesel oil. The results of RDF and combined distribution function (CDF) plots and also Voronoi tessellation analysis showed that the DBT molecules are adsorbed mainly by the MIL molecules compared with the n-dodecane which leads to DBT-removal. Also, it is found that the DBT molecules interact with the cation of MIL more than its anion. The results of domain analysis showed that the n-dodecane subset is stiffer than the MIL and DBT subsets. Altogether, the Fe-containing MILs can be a good sulfur extractor with high S-removal efficiency, lower toxicity than common volatile organic solvents, and low cost compared to the other common methods such as hydrodesulfurization (HDS), for future oil refinery applications.

The Ionic Liquid-H2O Interface: A New Platform for the Synthesis of Highly Crystalline and Molecular Sieving Covalent Organic Framework Membranes.

Covalent organic frameworks (COFs) are highly porous crystalline polymers with uniform pores and large surface areas. Combined with their modular design principle and excellent properties, COFs are an ideal candidate for separation membranes. Liquid-liquid interfacial polymerization is a well-known approach to synthesize membranes by reacting two monomers at the interface. However, volatile organic solvents are usually used, which may disturb the liquid-liquid interface and affect the COF membrane crystallinity due to solvent evaporation. Simultaneously, the domain size of the organic solvent-water interface, named the reaction zone, can hardly be regulated, and the diffusion control of monomers for favorable crystallinity is only achieved in the water phase. These drawbacks may limit the widespread applications of liquid-liquid interfacial polymerization to synthesize diverse COF membranes with different functionalities. Here, we report a facile strategy to synthesize a series of imine-linked freestanding COF membranes with different thicknesses and morphologies at tunable ionic liquid (IL)-H2O interfaces. Due to the H-bonding of the catalysts with amine monomers and the high viscosity of the ILs, the diffusion of the monomers was simultaneously controlled in water and in ILs. This resulted in the exceptionally high crystallinity of freestanding COF membranes with a Brunauer-Emmett-Teller (BET) surface area up to 4.3 times of that synthesized at a dichloromethane-H2O interface. By varying the alkyl chain length of cations in the ILs, the interfacial region size and interfacial tension could be regulated to further improve the crystallinity of the COF membranes. As a result, the as-fabricated COF membranes exhibited ultrahigh permeance toward water and organic solvents and excellent selective rejection of dyes.

Determination and correlation of phase equilibria of chiral magnetic ionic liquid aqueous two-phase systems with different inorganic salts at 298.15 K

Three novel chiral magnetic ionic liquids (MILs) with L-Pro anion were synthesized and applied to construct chiral magnetic ionic liquid aqueous two-phase systems (chiral MILATPs). This is the first reported chiral MILATPs and is showing great potential in the extractive resolution of racemic amino acids. In this work, aqueous two phase equilibrium binodal data of these chiral MILATPs ([CnMIM-Tempo][L-Pro](n = 2–4) + K2CO3/K3PO4/Na2CO3/Na2SO4 + H2O) were measured at temperature of 298.15 K. Three classical empirical equations including Merchuk equation were applied for the correlation of the experimental binodal data to obtain the binodal curve. Satisfactory correlation performances were achieved. The screening of inorganic salt revealed that K2CO3 and K3PO4 are better salting-out reagents than Na2CO3 and Na2SO4. Investigation of chiral MIL species demonstrated that chiral MIL with longer alkyl chain length of cation has better phase forming ability when the values of n are in the ranges of 2–4. Moreover, tie-line data for systems containing K2CO3 or K3PO4 were measured and correlated by Othmer-Tobias equation with satisfactory fitting performances (all R2 higher than 0.99). These results has ensured the reliability of these experimental data. The phase behaviors of these chiral MILATPs in this work has proved to meet the need of practical application and all these tested aqueous two-phase equilibrium data as well as the corresponding thermodynamic fitting can provide us useful reference for the future application in the field of extractive resolution of racemic amino acids.

Tuning the structure of pyridinolate-based functional ionic liquids for highly efficient SO2 absorption

A series of pyridinolate anion-functional ionic liquids (ILs) containing different kinds of cations were designed and prepared, including tri-n-hexyltetradecylphosphonium [P66614], tri-n-butylethylphosphonium [P4442], and 1,1,3,3-tetramethylguandinium [TMG] cations and pyridinolate [PyO] anions with different N positions. Densities and viscosities at different temperatures were measured because of their importance for the absorption of SO2. Effect of different structures on the absorption of SO2 was studied, including the type and the alkyl chain length of cations, and the N positions of [PyO] anions (2-, 3-, and 4-). Additionally, effects of SO2 concentration and temperature for absorption were investigated. Especially, up to 6.00 and 2.53 mol SO2 per mole IL could be obtained by [P66614][4-PyO] at 1 bar and 0.1 bar of SO2, respectively, when absorptions performed at 20 °C. The results indicate that (1) the aprotic cations weakened the cation⋯anion interaction and resulted in the released active sites on the anions, and (2) N position has an influence on charge distribution of [PyO] anions and resulted in the tunable absorption of SO2. Reversible SO2 absorption and [P66614][4-PyO] regeneration could be performed several times without losing efficiency. Furthermore, the mechanism of absorption was studied through FT-IR and NMR methods and the results showed that the absorption of SO2 by [P66614][4-PyO] includes physisorption and chemisorption.

(Invited) Diffusion Control of Metal Ions Close to Electrode in Ionic Liquid -Effect of Local Structure of Ionic Liquid-

Ionic liquids (ILs) have attracted keen attention due to its applicability to various kinds of electrochemical devices. However, we still lack enough knowledge of the interface structure and spatial distribution of chemical species during the electrochemical processes. In our previous study, we succeeded in the observation of the spatial distribution of Ag+ ions in ionic liquid solution close to the electrode under the applied potential using scanning electrochemical photoelectron spectroscopy (Scanning EC-PES) we originally developed. Interestingly, the diffusion layer where the concentration of metal ions is quite small (We named this region as “depletion layer”) was formed close to the electrode in a wide region. By a numerical simulation, we revealed that the metal ions diffused by the hopping-like mechanism, in which the apparent diffusion coefficient increased with increasing of the concentration of 'holes' (vacancies formed between IL molecules) acting as hopping sites.On the other hand, it can be anticipated that the local structure of ILs can be systematically controlled by changing of IL species (e.g. the alkyl chain length of imidazole cation, shape and size of anion), additive ions and/or temperature of solution. By using these techniques for controlling the local structure of ILs, we can strictly control the diffusion behavior of metal ions close to the electrode. In other words, we will be able to propose a new strategy for controlling the diffusion behavior of solutes in ionic liquid solutions close to the electrode. In this study, we investigated the factors for controlling the diffusion behavior of metal ion in IL electrolyte based on our proposing diffusion model, and revealed that the behavior of metal ions can be controlled by some factors.We investigated the additive effect using Li+ ion. In the case of the ~200 mM Ag+/BMI-TFSA((1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide) solution, the large depletion layer was formed close to the electrode, whereas the depletion layer was decreased when ~100 mM Li+ (as an electrochemically inactive additive) was added to the solution. This result indicates that the hopping-like diffusion was suppressed by the addition of the Li+ ion which efficiently occupied the holes (hopping sites) (Note that the depletion layer was formed by the fast hopping-like diffusion mechanism). On the other hand, when we added the excessive amount of additive (~500 mM Li+) to BMI-TFSA solution, a large depletion layer was formed again, indicating that the hopping diffusion was enhanced. This is due to that some Ag+ ions are drive out of the polar domain, and moved to the non-polar domain where the activation energy of hopping diffusion is relatively small. On the other hand, we carried out a similar experiment using HMI-TFSA instead of BMI-TFSA. We found that the hopping diffusion of Ag+ ion is enhanced compared with that in BMI-TFSA. This could also be explained by the local domain effect of ionic liquid. These results indicate that we can control the diffusion behavior of metal ions by adjusting the local structure of ionic liquid.

Counterion-specific shale hydration inhibiting performance of vinylimdazolium ionic liquids

The role of cation and the influence of the cation alkyl chain length of vinylimdazolium-based ionic liquid (IL) were studied previously to develop high-performance shale inhibitor for application in water-based drilling fluids (WBDFs). Results demonstrate that they have a considerable effect on the inhibition performance. However, the physicochemical properties can be tuned by changing the cation/anion combination. Therefore, the influence of anion type on the inhibiting performance must be investigated. In this study, we selected several vinylimdazolium-based ILs with different anions, such as bromide (Br−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−), and bis(trifluoromethylsulfonyl) (TFSI−). The size, solubility, hydrophilicity, and interaction in-between were tuned accordingly by changing the anion species. Results from linear swelling height, hot rolling recovery, and rheological measurements show that the IL with bromide anion has the most outstanding shale inhibiting performance. The anions influence the inhibitory performance of ILs in a distinct manner from cations by measuring the properties of Na–Bent dispersions added with different anion-based ILs. The former produces different abilities to suppress electric double layers and decreases the interlayer distance, whereas the latter mainly affects the interlayer distance. Despite different hydrophilic/hydrophobic properties, they have similar performance to inhibit the crystalline hydration and swelling. This condition is probably because they have a common cation that dominates the process of entering the interlayer void and narrowing interlayer spacing. Many hydrophilic ILs with anion Br− or BF4− have the capacity to strongly resist the repel interaction between clay particles and prompt aggregation, leading to better inhibitory performance. Combined with the previous result, cations and anions affect the IL inhibiting ability although their underlying mechanism is different. Thus, this work explored the relationship between inhibiting performance and IL moiety. The findings provide consolidate theoretical foundation for developing shale inhibitors for WBDFs.

Magnetic Microemulsions Stabilized by Alkyltrimethylammonium-Based Magnetic Ionic Liquids Surfactants (MILSs)

While traditional microemulsions are versatile media for nanoscience and nanotechnology, stimulus-responsive microemulsions are more challenging to realize, and only a handful of cases have been reported. We here introduce magnetic microemulsions (MMEs) stabilized by alkyltrimethylammonium-based magnetic ionic liquids surfactants (MILSs), paired with water as the polar phase, aliphatic oils as the nonpolar phase, and aliphatic alcohols as the cosurfactant. n-Hexane coupled with n(MILSs/1-butanol) = 1:4 showed the most excellent ability to form MMEs, and the range of the monophasic region was expanded with increasing alkyl chain length of MILSs cation. Classical oil-in-water (O/W), bicontinuous (BC) sponge structure, and inverse water-in-oil (W/O) subregions were clarified by conductivity method. Dynamic light scattering showed that the diameter of W/O microemulsions droplets were about 2-6 nm. Magnetic susceptibility and rheological measurements revealed that these MMEs are with high magnetic susceptibility and low viscosity, which show interesting potential applications based on a manipulation via external magnetic field. Moreover, these MMEs showed Newtonian-like flow behavior within respective subregions, and their magnetic susceptibility was not affected by the subregion structure but MILSs mass fraction.

Degradation of imidazolium ionic liquids in a thermally activated persulfate system

Thermally activated persulfate (PS) oxidation, a clean source of sulfate radicals (SO4•–), has been used as a promising advanced oxidation method for the treatment of organic contaminants. In this study, the degradation of ionic liquids (ILs) by thermally activated PS was investigated with 1-alkyl-3-methylimidazolium bromides (C4mimBr) as a model compound. The effects of various factors including temperature, initial IL and PS concentrations, solution pH, alkyl chain length of imidazolium cation, and common water constituents such as humic acid (HA), HCO3-and Cl- were evaluated. Results showed that C4mimBr can be completely degraded in 2 h at 60 °C, indicating effective removal of C4mimBr by thermally activated PS oxidation. The oxidation followed a pseudo-first-order kinetics model, and the rate constant increased with increasing temperature, PS concentration and initial solution pH. Alkyl chain length had no effect on the degradation. HA and Cl- had negative effects on C4mimBr removal, while 5 mM HCO3- increased C4mimBr degradation. Multiple intermediate products were identified by HPLC-MS/MS and the degradation pathway and mechanism were proposed. The free radicals generated in the activated PS system (e.g., SO4•– and •OH) showed different effects on the degradation. SO4•– radicals select to attack the substituted side chain of ILs cation, producing more chance for •OH to attack the imidazolium core. Moreover, toxicity tests using bioluminescent bacteria Vibrio Qinghaiensis sp.-Q67 and nematode C. elegans demonstrated efficient detoxification of CnmimBr treatment. These findings may offer an environmentally friendly approach for ILs treatment in aqueous solution.

Role of cation and alkyl chain length on the extraction of phenol from aqueous solution using NTf2-based ionic liquids: Experimental and computational analysis

In this study, the extraction behavior of several ionic liquids (ILs) containing the same anion, bis-(trifluoromethylsulfonyl)imide ([NTf2]) and a range of cations with different alkyl chain length are compared for the removal of phenol from aqueous solution. The [NTf2]− anion was selected due to its hydrophobic nature and low viscosity, which can contribute positively to mass transfer and to the removal efficiency of phenol, in combination with a range of imidazolium, pyrrolidinium and ammonium based cations. To study the effect of alkyl chain length on the extraction of phenol, the alkyl chain length attached to the imidazolium cation was varied from C2 to C12. The effect of process parameters such as IL to water volume ratio (VIL:Vw), phenol concentration, pH and extraction time were investigated. For a given alkyl chain length, the performance of the ILs followed the order: pyrrolidinium>imidazolium>ammonium. Increasing the alkyl chain length of the imidazolium cation resulted in decreasing removal efficiency of phenol. Around 89% removal of phenol was achieved in 3 min, at pH 2 and volume ratio (VIL: Vwater) of 1:3 at room temperature. The extraction of phenol into the ionic liquid phase was confirmed using Fourier Transform Infrared spectroscopy (FTIR). The interactions of phenol with the various studied ionic liquids were modeled using the Conductor like Screening Model for Real Solvents (COSMO-RS). The experimental results were explained based on hydrophobic-hydrophilic interactions between phenol and the ILs as revealed from the σ profiles.