Anion Of Ionic Liquid Research Articles

Exploring the influence of the type of anion in imidazolium ionic liquids on its thermal stability

Exploring the influence of the type of anion in imidazolium ionic liquids on its thermal stability

The Role of the Anion in Imidazolium-Based Ionic Liquids for Fuel and Terpenes Processing.

The potentialities of methylimidazolium-based ionic liquids (ILs) as solvents were evaluated for some relevant separation problems-terpene fractionation and fuel processing-studying selectivities, capacities, and solvent performance indices. The activity coefficients at infinite dilution of the solute (1) in the IL (3), γ13∞, of 52 organic solutes were measured by inverse gas chromatography over a temperature range of 333.2-453.2 K. The selected ILs are 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6], and the equimolar mixture of [C4mim][PF6] and 1-butyl-3-methylimidazolium chloride, [C4mim]Cl. Generally, low polar solutes follow γ1,C4mimCl∞ > γ1,C4mimPF6+C4mimCl∞ > γ1,C4mimPF6∞ while the opposite behavior is observed for alcohols and water. For citrus essential oil deterpenation, the results suggest that cations with long alkyl chains, such as C12mim+, promote capacity, while selectivity depends on the solute polarity. Promising results were obtained for the separation of several model mixtures relevant to fuel industries using the equimolar mixture of [C4mim][PF6] and [C4mim]Cl. This work demonstrates the importance of tailoring the polarity of the solvents, suggesting the use of ILs with mixed anions as alternative solvents for the removal of aliphatic hydrocarbons and contaminants from fuels.

Insights into the Charge Storage Mechanism of Binder-Free Electrochemical Capacitors in Ionic Liquid Electrolytes

Electrochemical capacitors (synonymously supercapacitors) working under an electrochemical double-layer charge storage mechanism (EDLC) are widely investigated because of their excellent power density and cycle life; however, their energy density is lower than those of lithium-ion batteries. Ionic liquids (ILs) are of great interest as electrolytes for EDLCs due to their wide operational voltage window. Here, we provide a systematic investigation on the influence of anions of ILs on the charge storage mechanism and electrochemical stability of EDLC electrodes. Two IL electrolytes, viz., [1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI)], having similar cations but different anions and carbon nanotube (CNT) electrodes are chosen for this study. The CNT//BF4:TFSI//CNT-based device showed superior electrochemical performance (∼69 F·g–1 gravimetric specific capacitance, ∼949 W·kg–1 power density, and ∼139 Wh·kg–1 energy density at 0.5 A·g–1) to CNT//EMIMBF4//CNT and CNT//EMIMTFSI//CNT devices. The device using a mixture of BF4:TFSI (1:0.5) electrolytes has an operating voltage of 0–3.8 V and specific capacitance retention of ∼45% at 0.5 A·g–1 after 500 cycles. In the case of the IL mixture (BF4:TFSI), the combined anion structure and their properties play very crucial part in the improvement of the electrochemical performance of the CNT//BF4:TFSI//CNT device. The assembled Teflon Swagelok-type cell could light up green (3.3 V) and red (2.1 V) light-emitting diodes for more than 5 min.

PANF supported polymeric ionic liquids: Amphiphilic microenvironment for efficient preparation of biodiesel

Efficient and green production is extremely essential to the development of society and environment, and supported polymeric ionic liquids as heterogeneous catalysts are the current research hotspot for chemists. In this study, imidazolium ionic liquids were supported on modified polyacrylonitrile fiber (PANF) by reversible addition fragmentation chain transfer (RAFT) polymerization, and a series of fiber-supported basic catalysts (PANF@VIm-nX) were obtained by ion exchange with different anions. The modified fibers were characterized by FT-IR, XRD, TGA, SEM, 13C CP-MAS NMR and ICP-MS. The results show that the modified fibers are successful and the catalysts have sufficient active sites and mechanical strength to meet the application requirements. Several supported poly(ionic liquid)s catalysts were used to promote the transesterification of methanol and soybean oil to produce biodiesel. The effects ofionicliquidswith different structures on the reaction yield were sufficiently investigated. The anions of ionic liquids and the length of hydrophobic alkyl chains have synergistic effects on the catalytic performance of the catalyst. The fiber catalyst (PANF@VIm-8OMe) with 8 carbon alkyl chains and OMe anion showed the optimal catalytic efficiency. The yield of biodiesel was as high as 95.4 % within 6 h with a catalyst dosage of 4 wt% and a methanol to oil ratio of 30:1 at 60 ℃. In addition, the fiber catalyst had excellent stability and durability, which could be recycled more than 6 times. Finally, the fiber could be twined on the stirring impeller of the reactor, indicating its potential industrial application prospect.

Application of ionic liquids in CO2 capture and electrochemical reduction: A review

As a new type of green solvent with non-volatility, high thermal stability, high conductivity and various adjustable properties, ionic liquid (IL) has been widely used in the capture and electrochemical reduction of carbon dioxide (CO2). To date, many studies have been made to investigate CO2 capture by using different types of ILs and CO2 electrochemical reduction (CO2ER) with ILs as either electrolyte or other catalytic active components. Some structure–activity relationships between the structure and adsorption or catalytic properties of ILs have been found. Herein, the absorption performances and mechanisms of conventional ILs, amino-functionalized ILs, non-amino functionalized ILs and supported ILs for CO2 capture, as well as the performances and action mechanisms of ILs as the electrolyte, electrolyte additive, and/or electrode modifier in the process of CO2ER are summarized. Many researches indicate that the unique interaction between the anion or cation of IL and CO2 has a significant contribution to promote the absorption and conversion of CO2. However, the ILs used for CO2 capture and electrochemical reduction should be further explored. Especially, a more in-depth investigation of the adsorption and catalytic mechanisms with the help of quantum chemical calculation, molecular simulation, and in situ characterization techniques is necessary. It is expected to design and develop more efficient ILs used for CO2 capture and conversion on a large scale.

Carbon materials derived from cyano-based IL@ZIF-8 composites for CO2 sorption separation systems

The sorption capacity and selectivity of pre- and post-carbonized cyano-based metal-organic framework (MOF) composite materials (cyano-based IL@ZIF-8) were investigated for the first time. The influence of the ionic liquid (IL) loading and number of cyano groups in the IL anion on a materials gas sorption separation performance was studied. Sorption-desorption equilibrium isotherms of CO2, CH4, and N2 were measured at 303 K in the ZIF-8, cyano-based IL@ZIF-8 composites and their derived carbon materials. The IL loading did not significantly affect the gas uptake of the carbon materials, while for the composites its main contribution was on the increase of the selectivity. The number of cyano groups in the anion played a key role in the sorption capacity and selectivity performance as it directly affects the N content and textural properties. The carbon material obtained from ZIF-8 (C_ZIF-8) precursor showed the best sorption capacity for all gases, just being surpassed by the C_15%[C6MIM][B(CN)4]@ZIF-8 carbon up to 1 bar. In terms of selectivity performance, carbons based on [C6MIM][B(CN)4]@ZIF-8 composites revealed to be equally or more selective than C_ZIF-8, increasing up to 65% between 0 and 1 bar depending on the mixture. The composites produced and their respective carbons demonstrated a promising application as sorbents for post-combustion CO2 separation systems.

Investigation of the extraction ability and mechanism of environmentally friendly ionic liquids for phenol in the model oil

The large number of phenolic compounds contained in coal tar and coal-converted oil seriously increased their cost of processing and transportation difficulties, so methods for efficient separation of phenolic compounds is of great industrial significance. Based on the flexible designability of ionic liquids, hydroxyl functional group that can interact with phenol were introduced into ionic liquid’s cations, eight ionic liquids were synthesized and their separation properties of phenol in model oil (methylbenzene) were studied. Cations of these ionic liquids have a significant influence the phenol extraction efficiency, which follows the order: [Ch]+ > [HEMIM]+. But the anions show a relatively small influence, and the order is: [Pro]- > [Lac]- > [Gly]- > [Ac]-. Other effects such as extraction temperature, molar ratio of phenol to ILs, extraction time and other factors on the extraction efficiency and distribution coefficient were investigated, also the optimum parameters were obtained. Hydroxyl modified ionic liquids showed good extraction performance for phenol, and the choline propionate ionic liquids showed the best separating capacity and were selected as the best extractant. The extraction performance was analyzed by 1H NMR and FT-IR spectra analysis. Hydrogen bond was confirmed to be one of the extraction mechanisms and we found that there was an optimal distance between the cation and anion of ionic liquids to form hydrogen bonds with phenol, also the π-π interaction between imidazole ring and benzene ring in phenol contributed to the extraction. In addition, the ionic liquid showed good recyclability and the regenerated ionic liquids could be reused five times with highly extraction efficiency.

Porous Polymer Supported Amino Functionalized Ionic Liquid for Effective CO2 Capture

A decrease in CO2 emissions is urgently required in the present situation due to the fast growth of carbon dioxide (CO2) in the atmosphere, which has caused a series of global climate issues. This study used an impregnation-evaporation method to immobilize an amino functionalized ionic liquid [C2OHmim][Lys] on a chromatographic column filler GDX-103 and create a novel supported ionic liquid. The results showed that the supported ionic liquid with 60 wt % ionic liquid content had the best adsorption performance at 40 °C, and the CO2 adsorption isotherm showed that the adsorption capacity at 0.1 MPa was 1.29 mmol CO2/g sorbent, which was 6 times greater than the adsorption capacity of the pure carrier. The sample with 60% ionic liquid content has an adsorption capacity of 1.02 mmol CO2/g sorbent under the condition of CO2/N2 mixed gas with 10% CO2 content. This is 43 times greater than the adsorption capacity of the pure carrier, and its adsorption performance is stable after three adsorption and desorption cycles. Through the rich porous structure of GDX-103, the ionic liquid is effectively supported and dispersed, which expands the contact area between CO2 and ionic liquid and enhances the mass transfer of CO2. At the same time, CO2 can be chemically bound to the groups on the anion of ionic liquid and be immobilized, so it has a high selective adsorption capacity of CO2, which makes it a great alternative to traditional CO2 adsorbents.

Controlling and tuning CO2 hydrate nucleation and growth by metal-based ionic liquids

The complex kinetic process of CO2 hydrate formation limits its applications of CO2 capture and sequestration et al. In this work, the effects of metal-based ionic liquids with different cations and anions on CO2 hydrate nucleation and growth was studied. The results showed that CO2 hydrate nucleation was promoted by the anions of [NiCl3]-, [MnCl3]-, [FeCl4]-, [C8MIM]+ and [C16MIM]+ ions due to the enhancement of local hydrogen-bonding network to construct crystal nuclei. The induction time of CO2 hydrate nucleation was decreased by 75.0% in the [C16MIM]FeCl4 aqueous solution. However, CO2 hydrate nucleation was inhibited by [C2MIM]+ and [ZnCl3]- anion. The gas storage capacity of CO2 hydrate was increased by mass transfer channels around the metal complex anions which could accelerate the diffusion rate of H2O and CO2 molecules. The co-effect between [C16MIM]+ cations and [FeCl4]- anions on CO2 hydrate growth was the strongest, which increased gas storage capacity by 16.1%. Hence, CO2 hydrate formation can be controlled and tuned by changing cations and anions of metal-based ionic liquids.

Modulation of Nanobubble Behaviors through Ionic Liquids during CO2 Electroreduction

CO2 electroreduction is a gas-consuming and -generating process, which is prevalently accompanied by the formation of bubbles. Bubbles adhered on the electrode surface severely affect the electrocatalytic efficiency. However, the formation and regulation of nanobubbles have not been studied in depth. In this work, the evolution behaviors of individual CO nanobubbles are investigated at gold nanoelectrodes, where CO is generated through CO2 electroreduction in ionic liquids (ILs). The recorded voltammograms demonstrate that the formation and stability of CO nanobubbles are enhanced because of improving the surface activity by adding ILs. Additionally, combining experimental results with classic nucleation theory, the regulation rules of different ILs on CO nanobubble nucleation are revealed: (i) with longer carbon chains, nanobubble formation can be facilitated by altering the surface energy and hydrophobic properties of the electrode through ILs; (ii) the increase of fluorine atoms in the anion of ILs decreases the driving force of nanobubble nucleation, while the introduction of amino groups into cations decreases the critical concentration of nanobubble nucleation. These results contribute to understanding CO nanobubbles and regulating them in further studies of CO2 electroreduction with ionic liquids.

Raman Wavelength Conversion in Ionic Liquids

We explore the use of room-temperature ionic liquids (ILs) as Raman wavelength converters. ILs provide an engineerable framework to design suitable liquids for wavelength conversion over a broad spectral range, through careful selection of the molecular structures of the IL anions and cations so that specific characteristics can be obtained, such as a desirable Raman shift, low Brillouin scattering, and good optical transmission in the pump and Stokes wavelengths. Applying such criteria, we demonstrate that 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA) is an effective medium for conversion of 532-nm pulses from a Q-switched Nd:YAG laser to 603 nm. This corresponds to an approximate 2200 cm−1 shift, which can be used to generate mid-infrared radiation through subsequent difference frequency generation for optical pumping of CO2 lasers. Threefold-higher Raman conversion efficiency is obtained in EMIM DCA compared with water under identical conditions in a proof-of-principle single-pass conversion setup, resulting in an efficient generation of multimillijoule, <6 ns duration, high-quality orange laser pulses in a wavelength region that is difficult to access at high energies. Consequently, we examine ILs representing two other classes of Raman-active functional groups and obtain conversion up to the fifth-order Stokes shift and first anti-Stokes shift. Through the tunable selection of their components and their useful dynamical properties, ILs provide a platform for efficient, simple, and alignment-tolerant high-energy Raman shifting with numerous industrial and technological applications.Received 16 June 2022Accepted 8 December 2022DOI:https://doi.org/10.1103/PhysRevApplied.19.014052© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasChemical Physics & Physical ChemistryOptical sources & detectorsStimulated Raman scatteringPhysical SystemsIonic fluidsMoleculesOrganic compoundsTechniquesInfrared techniquesAtomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsInterdisciplinary Physics

Effect of anions in ionic liquids on microstructure and oxidation characteristics of lignite

There is an urgent need for a green and efficient inhibitor to inhibit coal spontaneous combustion (CSC). Ionic liquids (ILs) have led to a growing interest because of eco-friendliness, sustainability, and excellent designable properties. Herein, we report some ILs, which are composed of [EMIM]+ cations and different anions (Cl–, [BF4]–, [OAC]–, [OTf]–). Anions show the characteristics of increased chain length and enhanced electronegativity of acid radical. The effect of the chain volume of anions and the strength of acidity on the microstructure of coal were measured by analyzing and comparing the changes of element morphology, Fourier Transform infrared spectroscopy structure parameters, and microcrystalline in this work. The results illustrate that with the increase of the anionic chain volume and the electronegativity of acid radical, the ILs appear the outstanding ability to destroy the lamellar diameter microcrystals and the structural abundance of aliphatic hydrocarbons of coal. With the enhancement of the electronegativity of anionic acid radical, the degree of reduction of CO and COO functional groups of coal and the ability of desulfurization rate are enhanced. The thermodynamic process demonstrates that the dry cracking temperature and ignition temperature can increase by 19.3 °C and 10.0 °C, respectively, resulting in coal may be inhibited during the oxidation. In additional, the thermal kinetic behaviors of samples were investigated by Starink models. Results indicated that the apparent activation energy of the inhibited samples can be increased from 51.96 kJ mol−1 of Un-tc to [EMIm][BF4]-tc 60.52 kJ mol−1 in the stages of thermal decomposition and combustion. The regular destruction characteristics of anions and cations on coal molecules to suggest hopeful prospects ILs as a novel and designable materials in the field of prevention CSC fire.

Plasticizing effect of 1‐butyl‐3‐methylimidazolium bromide content on poly(vinyl alcohol)

AbstractPVA/IL composites were successfully prepared with an ionic liquid (IL), 1‐butyl‐3‐methylimidazolium bromide and poly(vinyl alcohol) (PVA). The plasticizing effect of IL on PVA was investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and melt flow index (MI) measurements. FTIR analysis indicated that the anion (Br−) of IL could form hydrogen bonds with the hydroxyl groups of PVA. With an increase of IL, –OH absorption peaks of PVA/IL composites shifted to higher wavenumbers. DSC analysis showed that both melt and crystallization temperatures of the PVA/IL composites decreased as IL content increased. XRD analysis showed that the degree of crystallinity of the PVA/IL composites had a decreasing trend with an increase of IL. TGA showed that IL could effectively improve the thermal stability of PVA. The thermal stability of the PVA/IL composites decreased gradually with increasing IL content, but was higher than that of PVA. Thermal processing window (ΔT) analysis indicated that the addition of IL could significantly broaden ΔT of the PVA/IL composites, and their ΔT values first remained basically unchanged and then increased slightly with an increase of IL. In addition, MI analysis presented that the melt processability of the PVA/IL composites was not improved with the addition of IL and it was gradually improved with increasing IL content. In this work, PVA/IL composites with wide ΔT and high melt flow properties were prepared, which will lay a solid foundation for the preparation of high‐performance PVA fibers by melt spinning. © 2022 Society of Industrial Chemistry.

Anion and ether group influence in protic guanidinium ionic liquids.

Ionic liquids are attractive liquid materials for many advanced applications. For targeted design, in-depth knowledge about their structure-property-relations is urgently needed. We prepared a set of novel protic ionic liquids (PILs) with a guanidinium cation with either an ether or alkyl side chain and different anions. While being a promising cation class, the available data is insufficient to guide design. We measured thermal and transport properties, nuclear magnetic resonance (NMR) spectra as well as liquid and crystalline structures supported by ab initio computations and were able to obtain a detailed insight into the influence of the anion and the ether substitution on the physical and spectroscopic properties. For the PILs, hydrogen bonding is the main interaction between cation and anion and the H-bond strength is inversely related to the proton affinity of the constituting acid and correlated to the increase of 1H and 15N chemical shifts. Using anions from acids with lower proton affinity leads to proton localization on the cation as evident from NMR spectra and self-diffusion coefficients. In contrast, proton exchange was evident in ionic liquids with triflate and trifluoroacetate anions. Using imide-type anions and ether side groups decreases glass transitions as well as fragility, and accelerated dynamics significantly. In case of the ether guanidinium ionic liquids, the conformation of the side chain adopts a curled structure as the result of dispersion interactions, while the alkyl chains prefer a linear arrangement.

Force field refinement for reproducing experimental infrared spectra of ionic liquids.

We employ polarizable molecular dynamics simulations with the newly developed FFGenOpt parametrization tool to reproduce IR spectra of several ionic liquid cations and anions in the gas phase. Our results show that polarizable force fields in the bulk phase provide a reasonable compromise between computational effort and accuracy for investigating IR spectra when treating the transition from gas to liquid phase carefully. Although collectivity seems to play only a minor role, the liquid phase not only changes the electrostatic environment of the molecules but also introduces friction and intermolecular interactions altering the IR spectrum significantly. In addition to the classical force field approach, we also tested if the additional computational effort of machine learning potentials justifies their application in reproducing IR spectra. However, the main purpose of this work is to improve the quality of polarizable force fields concerning vibrations and not the prediction of IR spectra which can be better done with quantum-mechanical cluster approaches.

Separation of ethyl acetate and ethanol by imidazole ionic liquids based on mechanism analysis and liquid–liquid equilibrium experiment

Azeotrope of ethyl acetate (EAC) and ethanol (EA) generated in the synthesis of ethyl acetate (EAC), was difficult to separate by general distillation. Liquid-liquid extraction using ionic liquids (ILs) as extractants is a green and efficient method for separating azeotropes. To select the suitable ILs, the σ-profiles of EAC, EA, and different anions of imidazole ILs were obtained through the COSMO-SAC model. Then, the extraction mechanism of ILs in the EAC-EA system was discussed from the micro perspective, the interaction between ILs and EA was analyzed graphically by the interaction region indicator (IRI) using the Multiwfn and VMD, the interaction energy between ILs and EA/EAC were calculated by Gaussian 09. Finally, we selected 1-ethyl-3-methyl-imidazolium dihydrogen phosphate ([EMIm][H2PO4]), 1-butyl-3-methyl-imidazolium dihydrogen phosphate ([BMIim][H2PO4]), 1-ethyl-3- methyl-imidazolium hydrogen sulfate ([EMIm][HSO4]), and 1-butyl-3-methyl- imidazolium hydrogen sulfate ([BMIm][HSO4]) as the extractants based on the mechanism analysis. The Liquid-liquid equilibrium(LLE) data of EAC-EA-ILs were measured at 298.15 K under atmospheric pressure; the effects of ILs with different alkyl chain lengths of cations on the extraction efficiency were investigated, and the influence of ILs with different anions was also verified through experiments. Meanwhile, we adopted the NRTL activity coefficient equation to regress the experiment data, and the interaction parameters were optimized by the least square method using Matlab 2014.

Molecular Insight into the Ionic Conduction of Quaternary Ammonium and Phosphonium Cation-Based Ionic Liquids Using Dielectric and Spectroscopy Analyses.

We analyzed the primary properties of ionic liquids (ILs) comprising quaternary phosphonium cations and bis(trifluoromethylsulfonyl) amide anions and compared them with those of corresponding quaternary-ammonium-cation-based ILs. Broadband dielectric spectroscopy was used to confirm the coupling between the translational and orientational motions of ions, and our results demonstrated that the high ionic conductivity of the phosphonium-based ILs was attributed to their fast rotational dynamics. The differences between ILs with different cations were further evaluated using vibrational (Raman and terahertz) spectroscopy. The Raman spectroscopy data revealed that the cation structure affected the conformation and flexibility (conformational change) of the anion. Furthermore, terahertz spectroscopy allowed us to evaluate the relationship between ion transport and intermolecular interactions between the cation and anion of ILs.

High‐performance nano‐biocomposite ionic soft actuators based on microfibrillated cellulose/ionic liquid electrolyte membrane

AbstractHigh‐performance electro‐responsive ionic soft actuators with low actuation voltage, large bending strain, and ecofriendly functionalities have received great interest in soft robots, biomimetic robots, biomedical devise, flexible electronics, and wearable devices. Herein, we report a novel ionic soft actuator using biofriendly microfibrillated cellulose (MFC) and PEDOT:PSS, which exhibited a large peak‐to‐peak displacement (11.21 mm) mm under a sinusoidal excitation of 1.5 V at 0.1 Hz, low actuation voltage, wide driving frequency, excellent actuation durability (98% retention for 2 h), and excellent controllability, due to the strong ionic interactions of MFC fibers with cations and anions of ionic liquid (IL). Furthermore, the helical MFC‐IL ionic actuator was successfully designed, displaying that the radical displacements of the helical actuator could be controlled by changing the applied frequency and voltage. Therefore, the proposed ionic actuator as well as its helical design will offer an available pathway for guiding the development of artificial muscles, biomedical active devices, soft robots, flexible electronics, and soft electronics.

Ionic Liquids Effect on the Stability of 17-Electron Cation Product of the Electrochemical Oxidation of Cymantrene.

The oxidative electrochemistry of cymantrene, CpMn(CO)3 (1; Cp = [η5-C5H5]-), was examined in ionic liquids (ILs) composed of anions of varying Lewis base properties. It was observed that the cyclic voltammetric responses strongly depended on the nucleophilic properties of the IL anion. Still, all observations are consistent with the initial formation of 1+ followed by an attack from the IL anion. In bis(trifluoromethylsulfonyl)amide [NTf2]-based ILs, the process shows close to ideal electrochemical reversibility as the reaction between 1+ and [NTf2] anion is very slow. On the other hand, in tetrafluoroborate and trifluoromethanesulfonate-based IL, the oxidation of 1 shows different levels of electrochemical reversibility with a marked sign of anion attack to 1+. In contrast, 1 exhibits an irreversible oxidation process in hexafluorophosphate-based IL. The reaction rate constants for the interaction of 1+ with the different IL anions were estimated by fitting the experimental data to digital simulations of the proposed mechanism. Besides, the use of [NTf2]-based ILs as a supporting electrolyte in CH2Cl2 was also examined. The oxidation process of 1 shows a close to ideal electrochemical reversibility but low to non-chemical reversibility. This study illustrates the wide range of electrochemical environments available with ILs and demonstrates their limited utility for investigating the redox properties of metal carbonyl compounds. It also intends to warn the reader on how the IL media may influence an electrochemical study if care is not exercised.

Experimental and theoretical study on the extraction of keratin from human hair using protic ionic liquids

Keratin, the naturally derived biomaterials have been developed and widely applied in many different fields. Among the resources containing keratin, human hair is one of the most abundant natural fibers rich in keratin and one of the most abundant waste materials produced by humans. It is critical for both value-added human hair utilization and environmental protection if suitable solvents for the dissolution and regeneration of the keratin were developed. Ionic liquids (ILs) have been evidenced to be the green solvents to extract keratin from waste human hair. In this work, five novel Protic ILs were designed and synthesized in one step with inexpensive raw materials under mild conditions. The effect of different anions and cations, temperature, and water content on the dissolution ability of Protic ILs for human hair was investigated in depth. The best IL [MEA]HCOO with high solubilization capacity (9 h, 130 °C) for human hair was finally obtained by considering the time required for complete hair dissolution and the properties of regenerated keratin. The results of FTIR, XRD, and TGA showed that the α-helix structure of regenerated keratin was not destroyed. The recycling result indicates that the dissolution ability of [MEA]HCOO for human hair kept stable after 5 times recovery. Furthermore, the density functional theory (DFT) calculations and independent gradient model (IGM) analysis uncover the dissolution of human hair by ILs through synergistic interaction between the cations and anions of ILs.