Ternary Deep Eutectic Solvents Research Articles

Delignification of unbleached pulp by ternary deep eutectic solvents

Abstract The processing of lignocellulosic materials is very limited because of their low solubility in water and some organic solvents. Fifteen ternary deep eutectic solvents (DESs) were prepared and tested as solvents suitable for delignification of unbleached pulp. The selected ternary DESs are composed of quaternary ammonium salts and amino acids as hydrogen-bond acceptors, and organic acids and polyvalent alcohols as hydrogen bond donors, with molar ratios varying for the individual components. The delignification efficiency is significantly influenced by the degree of penetration of the solvent into the pulp fibre structure. Therefore, the density and viscosity analysis of individual solvents was performed. Unbleached beech pulp with initial kappa number 13.9 was treated with the prepared DESs. The kappa number indicates the residual lignin content or the bleachability of pulp. The efficiency of the solvents ranged from 1.4% to 28.1%. The most suitable for the pretreatment of fibres, based on lignin removal efficiency, were found to be three DESs, in the following order: malonic acid/choline chloride/1,3-propanediol (1:1:3) > choline chloride/acetamide/lactic acid (1:2:3) > choline chloride/urea/lactic acid (1:2:3).

Tunable and functional deep eutectic solvents for lignocellulose valorization

Stabilization of reactive intermediates is an enabling concept in biomass fractionation and depolymerization. Deep eutectic solvents (DES) are intriguing green reaction media for biomass processing; however undesired lignin condensation is a typical drawback for most acid-based DES fractionation processes. Here we describe ternary DES systems composed of choline chloride and oxalic acid, additionally incorporating ethylene glycol (or other diols) that provide the desired ‘stabilization’ function for efficient lignocellulose fractionation, preserving the quality of all lignocellulose constituents. The obtained ethylene-glycol protected lignin displays high β-O-4 content (up to 53 per 100 aromatic units) and can be readily depolymerized to distinct monophenolic products. The cellulose residues, free from condensed lignin particles, deliver up to 95.9 ± 2.12% glucose yield upon enzymatic digestion. The DES can be recovered with high yield and purity and re-used with good efficiency. Notably, we have shown that the reactivity of the β-O-4 linkage in model compounds can be steered towards either cleavage or stabilization, depending on DES composition, demonstrating the advantage of the modular DES composition.

Natural thymol-based ternary deep eutectic solvents: Application in air-bubble assisted-dispersive liquid-liquid microextraction for the analysis of tetracyclines in water.

Four new thymol-based ternary deep eutectic solvents were prepared and evaluated as the extractive phase in air-bubbles assisted dispersive liquid-liquid microextraction for extraction of tetracycline, doxycycline, and oxytetracycline from the water before high-performance liquid chromatography. The maximum extraction efficiencies were obtained using 400 μL of [choline chloride]:[thymol]:[nonanoic acid] in the molar ratio of 1:2:2 at pH = 5. The solvent was characterized by FTIR and NMR spectroscopy. The hydrophobicity of the deep eutectic solvent and its effect on the pH of water samples after mixing was also studied. Besides, the extraction efficiency of the ternary deep eutectic solvent was compared with that of two binary thymol-based deep eutectic solvents, including [choline chloride]:[thymol] and [thymol]:[nonanoic acid] at the same conditions. Under optimal conditions, limits of detection and quantification were 1.2-8.0 and 3.8-26.6μg/L, respectively. The linear ranges were 18.2-500μg/L for oxytetracycline, 26.6-500μg/L for tetracycline, and 3.8-500μg/L for doxycycline with the determination coefficients>0.9912. Intra- and inter-day relative standard deviations were 1.2-3.8 and 7.7-11.2%, respectively. The developed method was applied to the analysis of tetracyclines in unspiked and spiked environmental water samples, and the obtained recoveries were 74.5-95.4% with relative standard deviations of 1.2-4.0%.

Capture of Acidic Gases from Flue Gas by Deep Eutectic Solvents

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO2, CO2 and NO capture, are summarized based on the mechanism of absorption, physical interaction or chemical reaction. New strategies for improving the absorption capacity are introduced in this review. For example, a third component can be introduced to form a ternary DES to suppress the increase in viscosity and improve the CO2 absorption capacity. DESs, synthesized with halogen salt hydrogen bond acceptors (HBAs) and functionalized hydrogen bond donors (HBDs), can be used for the absorption of SO2 and NO with high absorption capacities and low viscosities after absorption, due to physicochemical interaction between gases and DESs. Emphasis is given to introducing the absorption capacities of acidic gases in these DESs, the mechanism of the absorption, and the ways to enhance the absorption capacity.

Computational modeling, fabrication, and characterization of the deep eutectic solvent-based green molecular cage for selective metronidazole extraction from plasma followed by UHPLC with diode array detector determination.

Four ternary deep eutectic solvents were computationally designed and synthesized, being used as candidate functional monomers in metronidazole molecular imprinting polymer synthesis, allowing selective extraction and determination by ultra high performance liquid chromatography with diode array detection. In terms of metronidazole selective extraction, the best results were obtained by (deep eutectic solvent)2 :(ethylene glycol dimethacrylate)11 , in which deep eutectic solvent is the functional monomer constructed by combining three components in 6:6:2 ratios of choline chloride:ethylene glycol:methacrylic acid. The effects of different parameters on molecular imprinted solid-phase extraction of metronidazole were thoroughly explored through screening design and response surface methodology. The adsorption mechanism findings show that the adsorption data are primarily fitted on the Freundlich model based on higher correlation coefficient. Kinetic experiments have shown that the mechanism of adsorption fits the pseudo-second-order model. The best extraction recovery (96.5%) was obtained in 25-min elution time, desorption temperature of 40°C, and 1.0mL ACN as eluent. Metronidazole was measured by a validated ultra high performance liquid chromatography with diode array detection method. The calibration of the method was linear in the range of 0.1-10 μg/mL with limits of detection and quantification of 0.03 and 0.1 μg/mL, respectively. The method was successfully applied for the determination of metronidazole in human plasma.

Exploration of a ternary deep eutectic solvent for the efficient extraction of plantamajoside, acteoside, quercetin and kaempferol from Plantago asiatica L.

In the present study, ternary deep eutectic solvent-based ultrasound-assisted extraction was developed for the efficient extraction of plantamajoside, acteoside, quercetin and kaempferol from Plantago asiatica L. Six kinds of choline chloride-based ternary deep eutectic solvents (TDESs) were prepared as potential extraction solutions. In order to obtain optimal extraction efficiency, a series of extraction conditions were investigated by single-factor test and orthogonal test. The extraction efficiency of choline chloride/lactic acid/ethylene glycol (ChCl-LA-EG) was much higher than that of other TDESs. ChCl-LA-EG-11 synthesised with choline chloride, lactic acid and ethylene glycol (1:4:2) was considered to have a higher extraction efficiency. The optimal ultrasound-assisted extraction conditions were as follows: water content in ChCl-LA-EG-11, 50%; extraction temperature, 70°C; ratio of solid/liquid, 20 mg/mL; ultrasonic power, 60 W; extraction time, 35 min; pH of the solution, 8. Under the optimal extraction conditions, the extraction efficiencies of plantamajoside, acteoside, quercetin and kaempferol were 3.83 ± 0.41, 4.23 ± 0.45, 0.56 ± 0.15 and 0.19 ± 0.08 mg/g, respectively. The extraction efficiency of the total target components was 9.21 ± 0.63 mg/g, which was much higher than that of conventional solvents (water, methanol, ethanol, 50% methanol, 50% ethanol). The target components were isolated efficiently from the TDES solution by an AB-8 macroporous resin column with a recovery rate of 95.6%. This study demonstrated that TDESs possessed excellent physical and chemical properties and had enormous potential for active component extraction of traditional Chinese medicinal materials.

Highly efficient CO removal by active cuprous-based ternary deep eutectic solvents [HDEEA][Cl] + CuCl + EG

Carbon monoxide (CO) is a kind of impurity gas in hydrogen (H2), resulting to catalyst poisoning in proton-exchange-membrane fuel cells (PEMFCs). On the other hand, CO is harmful to human health due to its colorlessness, odorlessness and high toxicity. In this contribution, a series of active cuprous-based ternary deep eutectic solvents (DESs) with 2-diethylaminoethanol chloride ([HDEEA][Cl]) plus cuprous chloride (CuCl) plus ethylene glycol (EG) at different molar ratios (1:1:4, 1:1:2 and 1:1:1) were designed and prepared. Physical properties such as density and viscosity of these DESs were measured at different temperatures. CO capture by these DESs were investigated at different concentrations of CO and different temperatures. It was found that the capture capacities of 0.203 and 0.564 mol CO per mole DES could be reached by [HDEEA][Cl] + CuCl + EG with n[HDEEA][Cl]:nCuCl:nEG = 1:1:4 at 293.2 K and 1 bar or 5 bar, respectively. FT-IR method was used to investigate the mechanism of CO removal. These results suggested that the presence of Cu(I) is crucial for efficient capture of CO by these ternary DESs while − OH groups and EG could release the activity of Cu(I). Furthermore, the thermodynamic properties such as the Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) for CO capture by [HDEEA][Cl] + CuCl + EG (1:1:4) were obtained, and ΔH was the main driving force for CO capture.

Cold-induced Homogenous Liquid–Liquid Extraction Performed in a Refrigerated Centrifuge Combined with Deep Eutectic Solvent-based Dispersive Liquid–Liquid Microextraction for the Extraction of Some Endocrine Disrupting Compounds and Hydroxymethylfurfural from Honey Samples

A cold-induced-homogeneous liquid–liquid extraction method combined with deep eutectic solvent-based dispersive liquid–liquid microextraction has been done to extract several endocrine disrupting compounds (phenol, p-chlorophenol, p-nitrophenol, octylphenol, methyl paraben, ethyl paraben, butyl paraben, and bisphenol A) and hydroxymethylfurfural from honey samples before their determination by gas chromatography–mass spectrometry. In this method, two ternary deep eutectic solvents including tetrabutyl ammonium chloride: dichloroacetic acid: ethylene glycol (hydrophilic) and tetrabutyl ammonium chloride: dichloroacetic acid: decanoic (hydrophobic) acid deep eutectic solvents are prepared and used as the extraction solvents in the developed method. The analytes are extracted by a two-step extraction procedure in which they are first extracted into the hydrophilic deep eutectic solvent and then transferred into a few microliters of the hydrophobic deep eutectic solvent for more concentration. In both steps, phase separation is done by centrifugation at low temperature. The method was optimized and validated and the results showed that the method had low limits of detection (0.21–0.50 ng g−1) and quantification (0.72–1.7 ng g−1), wide liner ranges, and an acceptable repeatability (relative standard deviation≤12). Lastly, the developed method was applied on different honey samples and bisphenol A, p-nitrophenol, and hydroxymethfurfural were found in some of them.

Constructing the frustrated Lewis pairs within N,S-codoped carbon to reveal the role of adjacent heteroatom sites for highly effective removal of heavy metal ions

Heteroatom doping is a promising strategy for improving adsorption performance of cost-effective carbon materials for heavy-metal ions from wastewater. However, the lack of theoretical research restricts its development. Herein, theoretical simulations successfully predict that the short distance between the N and S sites is a key factor for the N,S-codoped carbon with a higher adsorption capacity than that of the single doping carbon. Inspired by this interesting finding, a low-energy and ultrafast approach is proposed to prepare N,S-codoped carbon within only 10 s from ternary deep eutectic solvents. Benefiting from the unique dual-doped architecture, the adsorption capacity of the N,S-codoped carbon for Cr(VI) is significantly enhanced to 564.7 mg/g in comparison with single doped carbon (396.2 mg/g) and pristine carbon (186.4 mg/g). The further calculations of energy and electronic structure reveal that adjacent –NH3+ and –SO2– groups can generate frustrated Lewis pairs (FLPs). Such FLP-type sites can promote the adsorption and reduction of Cr(VI) ions due to enhanced electron transfer between functional groups and Cr(VI) ions. This work provides an in-depth comprehension and guidance for synthesis of heteroatom-codoped carbon-based materials with excellent separation performance for heavy metal ions.

Ternary glycerol-based deep eutectic solvents: Physicochemical properties and enzymatic activity

The present study investigates deep eutectic solvents (DESs) as potential media for enzymatic hydrolysis. A series of ternary ammonium and phosphonium-based DESs were prepared at different molar ratios by mixing with aqueous glycerol (85%). The physicochemical properties including surface tension, conductivity, density, and viscosity were measured at a temperature range of 298.15 K – 363.15 K. The eutectic points were highly influenced by the variation of temperature. The eutectic point of the choline chloride: glycerol: water (ratio of 1: 2.55: 2.28) and methyltriphenylphosphonium bromide:glycerol:water (ratio of 1: 4.25: 3.75) is 213.4 K and 255.8 K, respectively. The stability of the lipase enzyme isolated from porcine pancreas (PPL) and Rhizopus niveus (RNL) toward hydrolysis in ternary DESs medium was investigated. The PPL showed higher activity compared to the RNL in DESs. Molecular docking simulation of the selected DES with the substrate (p-nitrophenyl palmitate) toward PPL was also reported. It is worth noting that ternary DES systems would be viable lipase activators in hydrolysis reactions.

Understanding the CO2 capture performance by MDEA-based deep eutectics solvents with excellent cyclic capacity

Solvents for CO2 capture with efficient regeneration are essential for industrial applications. Here, three methyldiethanolamine (MDEA) based deep eutectic solvents (DESs) were developed and their performance for CO2 uptake and regeneration was evaluated. Density functional theory (DFT) calculation and molecular dynamics (MD) simulations were performed to elucidate the features of DES and the DES interaction with CO2. The CO2 absorption performance is dependent on the hydrogen bond acceptor (HBA). [Monoethanolamine hydrochloride (MEAHCl)][MDEA] exhibits the best CO2 absorption performance, which is further enhanced by the addition of monoethanolamine (MEA), reaching 13.5 wt% after 6 h of absorption at 25 °C when the ratio of MEAHCl, MDEA, and MEA at 1:3:0.5. Both DFT calculation and MD simulations reveal that the CO2 interaction with [MEAHCl][MDEA] is via the –NH2 group in MEAH+ and the –OH group in MDEA, also confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) results. The ternary DES of [MEAHCl][MDEA][MEA] with low desorption activation energy exhibits excellent cyclic capacity after 5 cycles of regeneration, offering an efficient and low-cost CO2 capture system for industrial applications.

Efficient and remarkable SO2 capture: A discovery of imidazole-based ternary deep eutectic solvents

Developing an adsorbent with optimal absorption capacity for SO2 elimination has been an important issue, yet a great challenge remains. Herein, we initiated a series of ternary deep eutectic solvents (DESs), consisting of diethylenetriamine (DETA), ethylene glycol (EG) and 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) with various molar ratio for the systematical investigation of SO2 absorption. It was found that DES with the molar ratio of 2: 1: 2 (DETA: EG: [Emim]Cl) exhibits remarkable absorption capacity (1.02 g SO2/g DES) and robust reusability for SO2 at room temperature and ambient pressure, which is distinctively higher than most of the reported binary DESs so far. Moreover, FT-IR, 1H NMR, 13C NMR together with DFT calculations were adopted to clarify the absorption mechanism for SO2. It indicates that the remarkable absorption capacity might be ascribed to the existence of multiple absorption sites. Therefore, this study offers a promising alternative for the design and preparation of highly effective absorbents for gas elimination.

2D amorphous bi-metallic NiFe nitrides for a high-efficiency oxygen evolution reaction.

Two-dimensional bi-metallic NiFe nitrides (2D NiFe-N) are successfully synthesized in the designed ternary deep eutectic solvents under the guidance of DFT calculations. Taking advantage of the unique properties of large-size, ultrathin amorphous 2D structure and modulable electronic structure, the NiFe0.05-N exhibits extraordinary OER performance with relatively low overpotential of 238 mV at 10 mA cm-2 and durable stability.

Protic ethanolamine hydrochloride-based deep eutectic solvents for highly efficient and reversible absorption of NH3

Ammonia (NH3) is essential for nitrogen fertilizer and is also considered as a promising energy carrier recently. In considering the role of NH3 for energy storage, the health and environmental risks from NH3 emission must be minimized and efficiently eliminated. To this end, a wide range of materials such as metal halides, ionic liquids and porous materials have been examined for NH3 absorption. Deep eutectic solvents (DESs) with unique properties and low cost are considered as potential solvents for absorbing NH3. Herein, we report a DES composed of protic ethanolamine hydrochloride (EACl), weakly acidic resorcinol (Res) and neutral glycerol (Gly) can absorb 0.240 g NH3/g DES for EACl/Res/Gly (1:4:5) at 293 K and 0.1 MPa, which is much higher than most of reported DESs. The absorption mechanism of NH3 is hydrogen-bonding interaction from the results of NMR and FT-IR spectra. The ternary DESs EACl/Res/Gly have abundant hydrogen-bonding sites to absorb NH3 without structural damage, in which EACl and Res play a major role in the interaction with NH3, while Gly is helpful for structural stability during NH3 absorption. Besides, DES EACl/Res/Gly (1:4:5) has good reversibility, excellent NH3/CO2 selectivity, is a potential NH3 absorption and storage material for industrial application.

Promoted absorption of CO at high temperature by cuprous‐based ternary deep eutectic solvents

AbstractAchieving efficient dissolution of carbon monoxide (CO) in the solvent is very helpful for the implementation of carbonylation reaction at ambient pressure. However, almost all of common solvents show very low solubilities of CO at high temperature. Herein, a series of cuprous‐based ternary deep eutectic solvent (DES) was prepared by mixing imidazolium hydrochloride with CuCl and ZnCl2. The ternary DES [BimH]Cl‐CuCl‐1.0ZnCl2 exhibited very large CO absorption capacity (0.075 mol mol−1, 1 bar) even at a high temperature (353.2 K), which is superior to all of the reported absorbents. Moreover, the ternary DES [BimH]Cl‐CuCl‐1.0ZnCl2 could further promote the reactive absorption of CO to conduct the aminocarbonylation reaction effortlessly at ambient pressure, and thus the targeted products benzamides were obtained in 70–97 yields. We believe that this finding opens a new way to design advanced solvents for efficient capture of CO at high temperature.

Selective separation and inexpensive purification of paclitaxel based on molecularly imprinted polymers modified with ternary deep eutectic solvents

Paclitaxel (PTX) is a powerful anticancer natural product, with its separation and purification having been widely studied. In this work, new molecular imprinted polymers (MIPs) using deep eutectic solvents (DESs) with different molar ratios were prepared as functional monomers. These were then used as adsorbents in solid phase extraction (SPE) for the separation of PTX from its structural analogs. The polymers were characterized by energy disperive X-rays (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FT-IR). The results suggested that the formative regular DES-MIPs had an even pore-size distribution and a large specific surface area. The dynamic adsorption and static adsorption showed that the DES-MIPs had excellent adsorption performance, with a maximum adsorption capacity and optimum adsorption time of 87.08 mg/g and 180 min, respectively. The selective adsorption experiments showed that the material had outstanding selectivity, and the maximum selectivity factor was 6.20. For stability, after six consecutive adsorption and desorption cycles, the DES-MIPs maintained the perfect stability and reusability. Furthermore, the fabricated SPE column was successfully utilized for extracting and eluting PTX. This study provides a reliable protocol for the separation and purification PTX from its structural analogs and the DES-MIPs materials have excellent potential application value in pharmaceutical industry.

Efficient dissolution of lignin in novel ternary deep eutectic solvents and its application in polyurethane

Novel ternary deep eutectic solvents (DESs) were designed to efficiently dissolve the lignin for synthesizing the lignin-containing rigid polyurethane foam (LRPUF). These ternary DESs were constituted by choline chloride (ChCl), two hydrogen bond donors – glycerol (Gly) and polyethylene glycol (PEG-400). The maximum solubility of lignin in the sample DES-2 (ChCl:Gly:PEG-400 = 1:2:2) could up to 66.70 g/100 g solvent at 60 °C due to the hydrogen bonds are the main driving force, which was confirmed by the largest hydrogen bond basicity parameter β value and disappearance of crystalline peak. The main structure of the lignin did not change after dissolution in DES-2. The content of phenolic and total hydroxyl groups of the regenerated lignin increased, with reduction in their average molecular weights and polydispersity, indicating that the dissolution and regeneration of lignin in these ternary DESs can make it more homogeneous. The regenerated lignin was partially replacing for polyols in the LRPUF synthesis, the lignin replacement rate could up to 58.6% with good mechanical properties. The findings add to our understanding for efficient dissolution of lignin in DESs and for synthesizing the highly LRPUF.

Deep eutectic solvent-induced high-entropy structures in boron nitride for boosted initiation of aerobic oxidative desulfurization of diesel

Depending on the synthetic method, the heteroatom-doped hexagonal boron nitride (h-BN) catalysts can have different configurational entropies possessing various atomic short-range orderings or phase separations, leading to complex grain boundaries for catalytic reactions. Herein, several carbon and oxygen co-doped h-BN (BCNO) catalysts with different atomic orderings were synthesized from the ternary deep eutectic solvents (DES). The experimental results indicated the low steric resistance DES induced high-entropy structures (HES) in the BCNO, which involved a high density of grain boundaries. The HES was investigated as a catalytic booster for the radical initiation of aerobic oxidative desulfurization (ODS) of diesel. As a result, the optimized BCNO catalyzed ODS process owned the shortest induction period, rendering the complete aerobic oxidation of refractory sulfur compounds in 6 h.

Synthesis cyclic carbonates with BmimCl-based ternary deep eutectic solvents system

A novel 1-Butyl-3-methylimidazolium chloride (BmimCl)-based ternary deep eutectic solvents system was developed and employed to convert CO2 into cyclic carbonates under mild conditions. Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric and differential thermal analyses (TG-DTA) were used to character the DESs. Besides, the impacts of reaction parameters and substrate ranges on cycloaddition reaction were also investigated. Under the optimized reaction conditions, the yield of propylene carbonate (PC) was about 98.0 % over BmimCl/Boric acid (BA)/Glutaric acid (GA) (7/1/1, molar ratio). In addition, the BmimCl-based ternary DESs are easy to recycle and indicates excellent reusability. The mechanism of epoxide activated by hydrogen bonds and epoxide ring opening was proposed. The BmimCl-based ternary DESs will be viewed as an innovative system for cycloaddition of CO2 with epoxides and it will supply a novel class of DESs for other possible applications.

Morphology Modulation of Ionic Surfactant Micelles in Ternary Deep Eutectic Solvents.

Deep eutectic solvents (DES) are potentially greener solvents obtained through the complexation of simple precursors which, among other applications, have been investigated in recent years for their ability to support the self-assembly of amphiphilic molecules. It is crucial to understand the factors which influence surfactant solubility and self-assembly with respect to the interaction of the surfactant molecule with the DES components. In this work, small-angle neutron scattering (SANS) has been used to investigate the micellization of cationic (CnTAB) and anionic (SDS) surfactants in a ternary DES comprising choline chloride, urea, and glycerol, where the hydrogen bond donors are mixed in varying molar ratios. The results show that in each case either globular or rodlike micelles are formed with the degree of elongation being directly dependent on the composition of the DES. It is hypothesized that this composition dependence arises largely from the poor solubility of the counterions in the DES, especially at low glycerol content, leading to a tighter binding of the counterion to the micelle surface and giving rise to micelles with a high aspect ratio. This potential for accurate control over micelle morphology presents unique opportunities for rheology control or to develop templated syntheses of porous materials in DES, utilizing the solvent composition to tailor micelle shape and size, and hence the pore structure of the resulting material.