Deep Eutectic Solvent System Research Articles

Air Assisted Dispersive Liquid–Liquid Microextraction (AA-DLLME) Using Hydrophilic–Hydrophobic Deep Eutectic Solvents for the Isolation of Monosaccharides and Amino Acids from Kelp

Air assisted dispersive liquid–liquid microextraction (AA-DLLME) using hydrophilic–hydrophobic deep eutectic solvents (DES) was developed for the simultaneous isolation of monosaccharides and amino acids with wide ranges of polarities from kelp using high performance liquid chromatography (HPLC). A response surface methodology (RSM) on a Box–Behnken design (BBD) model was employed to identify the optimal extraction parameters. Air assisted dispersive liquid-phase microextraction performed using the optimum deep eutectic solvent system, five push–pull cycles, a ratio of solid to liquid equal to 3 mg·mL−1, 10% (w/v) NaCl, and a centrifugation time of 6 min provided the best analytical performance. The optimal extracted concentrations of d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-valine in kelp were 16.7 ± 0.2, 8.6 ± 0.2, 2.6 ± 0.1, and 1.6 ± 0.1 mg·g−1, respectively. The method recoveries for d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-tyrosine were from 87 to 102%, 84 to 103%, 87 to 104%, and 85 to 103%. The relative standard deviations (RSDs) (n = 4) for the intra-day and inter-day determinations were <6.17%.

Application of the Preferential Solvation Viscosity Model to Binary Liquid Mixtures: Aqueous, Nonaqueous, Ionic Liquid, and Deep Eutectic Solvent Systems

The preferential solvation (PS) viscosity model was used to correlate binary liquid viscosities of aqueous, nonaqueous, nonpolar–polar, molecular solvent–ionic liquid (IL), and molecular solvent–de...

Strong Microheterogeneity in Novel Deep Eutectic Solvents.

With the increasing application of template assisted syntheses in deep eutectic solvents and successful application of hydrophobic deep eutectic solvents in extraction processes, where microheterogeneity plays a major role, suggestions for novel deep eutectic solvents which exhibit strong microheterogeneity are desirable. Therefore, classical molecular dynamics simulations were carried out on deep eutectic solvent systems constructed of choline chloride and some of its derivatives mixed with ethylene glycol in a molar composition of 1 : 2 since this is the optimal parent composition. The derivatives consisted of a series of elongated alkyl side chains and elongated alcohol side chains. Of these series only choline chloride ethylene glycol has been investigated experimentally, the other systems are suggested and theoretically investigated as possible target for synthesis. Our domain analysis supported by the clear distinction of polar and nonpolar parts from the electrostatic potentials reveals that strong microheterogeneity within these novel hypothetical deep eutectic solvents exists. Rather stretched than crumbled side chains maximize possible interaction sites for both polar and nonpolar parts which make the suggested compounds valuable objectives for experiments in order to exploit the microheterogeneity in deep eutectic solvents.

Modeling of Solid–Liquid Equilibria in Deep Eutectic Solvents: A Parameter Study

Deep eutectic solvents (DESs) are potential alternatives to many conventional solvents in process applications. Knowledge and understanding of solid–liquid equilibria (SLE) are essential to characterize, design, and select a DES for a specific application. The present study highlights the main aspects that should be taken into account to yield better modeling, prediction, and understanding of SLE in DESs. The work is a comprehensive study of the parameters required for thermodynamic modeling of SLE—i.e., the melting properties of pure DES constituents and their activity coefficients in the liquid phase. The study is carried out for a hypothetical binary mixture as well as for selected real DESs. It was found that the deepest eutectic temperature is possible for components with low melting enthalpies and strong negative deviations from ideality in the liquid phase. In fact, changing the melting enthalpy value of a component means a change in the difference between solid and liquid reference state chemical potentials which results in different values of activity coefficients, leading to different interpretations and even misinterpretations of interactions in the liquid phase. Therefore, along with reliable modeling of liquid phase non-ideality in DESs, accurate estimation of the melting properties of their pure constituents is of clear significance in understanding their SLE behavior and for designing new DES systems.

Deep eutectic solvents used as the green media for the efficient extraction of caffeine from Chinese dark tea

In recent years, more and more attention are paid to the green media in the extraction field. Deep eutectic solvents (DESs) are considered as excellent substitutes to traditional organic solvents and ionic liquids (ILs). In this work, DESs were used to extract caffeine from Chinese dark tea (CDT), then caffeine was recovered from the crude DES extract using macroporous resins. The factors affecting the solid-liquid extraction, including DES concentration, liquid-solid ratio, extraction time, extraction temperature, and system pH were studied in the single factor experiments. The Kamlet-Taft polarity parameters of DESs were determined to analyze the proper hydrogen-bond interaction between DESs and caffeine. Then the major factors of DES concentration, liquid-solid ratio, and extraction time were optimized by response surface methodology (RSM). The results showed that the maximum extraction yield of 26.78 mg/g were obtained using the DES choline chloride-lactic acid (ChCl-LA) as extractant under the optimized conditions. Moreover, the kinetics model of caffeine extraction was established using the Fick’s Second Law, the experimental results were well fitted by this model. This extraction of caffeine from CDT using DESs is much simpler and environmentally friendly with low cost and high extraction efficiency.

Novel acidic eutectic mixture as peroxidase mimetics for oxidative desulfurization of model diesel

A new generation of green solvent, deep eutectic solvents (DESs), are being received increased interest in the fields of organic synthesis, electrochemistry, catalysis and oxidative desulfurization (ODS) process. Despite possessing high ODS activity, little is known for the mechanism of the excellent desulfurization performance of DES. In this study, a class of acidic eutectic mixture was prepared with different molar ratios of acetamide and glutaric acid. It was found that desulfurization process was significantly affected by the composition of prepared DES. Under optimal conditions, the desulfurization efficiencies of acetamide/glutaric acid (molar ratio 1 : 2) DES was capable to reach up to 99% within only 3 h.Density functional theory (DFT) calculation revealed that acetamide/glutaric acid DES possessed intrinsic peroxidase-like property and reduced greatly TS barriers in oxidation process. The synergy cooperation of acetamide and carboxylate likes the active site of enzyme, achieving the catalytic oxidation of dibenzothiophene (DBT). In addition, this DES system was successfully applied for the deep oxidation desulfurization of real fuels, which demonstrated extraordinary catalytic performances.

Electrodeposition of Pd from a deep eutectic solvent system: effect of additives and hydrodynamic conditions

ABSTRACTElectrodeposition of palladium from a mixture of choline chloride/urea/palladium(II) chloride (deep eutectic solvent) has been carried out by direct and pulse current electrodeposition. The influence of five organic additives, current mode (direct current vs. pulsed current) and hydrodynamics on the surface morphology of the electrodeposited palladium films was investigated. The surface morphology and thickness of the palladium layers produced was determined by scanning electron microscope and energy dispersive X-ray fluorescence spectroscopy. The experimental results showed that the surface morphology of the palladium deposits could be affected significantly either by applying pulse current and/or addition of organic additives. Current mode, electrolyte agitation and surface effects of the selected additives mutually interfere with each other, causing changes in the microstructure of the deposits (coarse → nodular/smooth). It was possible to improve the palladium deposit quality and metal deposition rate by addition of appropriate additives and by applying pulsed current.

Electrochemical Investigation of the Cu2+ → Cu1+ Reduction Reaction in Ethaline Deep Eutectic Solvent

Deep eutectic solvents (DES) are inexpensive, non-flammable, biodegradable, and possess good electrochemical stability. Therefore, they are gaining attention as potential next-generation electrolytes for electrochemical applications such as energy storage and electrodeposition. For use in these applications, knowledge of the transport and electrochemical kinetics properties when using DES electrolytes is critically important. However, accurate measurements of these properties using traditional electrochemical methods such as cyclic voltammetry (CV) and polarization on RDE can be quite challenging in DES systems. Specifically, the highly viscous and thus poorly conducting DES electrolytes cause excessive ohmic polarization rendering the current distribution on the RDE to be highly non-uniform. Furthermore, during unsteady-state measurements such as CV, ohmic electrolyte resistance introduces non-linear changes in the surface potential thereby complicating quantitative CV analysis. In this talk, we will discuss such issues using the well-known Cu2+ + e ↔ Cu1+ reaction in a 1:2 choline chloride – ethylene glycol (ethaline) model DES system. We will present guidelines to circumvent pitfalls so as to obtain reliable transport and kinetics data [1]. Of these recommendations, we will focus on the importance of real-time compensation during CV and the use of electrode configurations, such as microelectrodes, which provide uniform secondary current distribution. Finally, we will report on our efforts to obtain accurate measurements of the kinetics parameters (exchange current density, charge transfer coefficients) associated with Cu2+ + e ↔ Cu1+ reaction. Mechanistic aspects of the Cu2+ + e ↔ Cu1+ reaction which lead to its sluggish electrochemical kinetics in DES media will also be discussed. D. Shen, K. Steinberg, and R. Akolkar, J. Electrochem. Soc., 165, E808 (2018).

Choline chloride-based deep eutectic solvent systems as a pretreatment for nanofibrillation of ramie fibers

As a new type of green solvents, deep eutectic solvents (DESs) were used as pretreatment media for the nanofibrillation of ramie fibers (RFs). Two DESs, choline chloride-oxalic acid dihydrate (CO) and choline chloride-urea (CU), were formed at 100 °C and then applied to decompose RFs. The DES-pretreated fibers were nanofibrillated using a planetary ball mill, and their properties were analyzed. During the DES pretreatment, CU DES could only dissolve some of hemicelluloses in raw RFs, while CO DES could degrade some oligosaccharides and a part of amorphous cellulose to loosen the fiber structure. Therefore, only the CO DES pretreatment could significantly enhance nanofibrillation of the RFs with a low hemicellulose content in this study, as indicated by the decrease of milling time (from 11 to 5 h) to obtain desirable cellulose nanofibrils (CNFs). After 7 h CO DES pretreatment at room temperature and a subsequent ball milling process, a turbid and gel-like CNF suspension with a mean equivalent spherical diameter of 262 nm was obtained from RFs, and the mass yield of CNFs reached 94.06%. The CNFs also showed a crystallinity index of 66.51% and a thermal stability with Tmax = 322.6 °C, and the produced CNF film had a tensile strength of 52 MPa. Overall, the CO DES pretreatment has great potential for use in the production of CNFs from RFs.

Facile Extraction of Thermally Stable and Dispersible Cellulose Nanocrystals with High Yield via a Green and Recyclable FeCl3-Catalyzed Deep Eutectic Solvent System

In the current work, a green and recyclable FeCl3-catalyzed deep eutectic solvent system (F-DES) was invented to fabricate cellulose nanocrystals (CNCs) with a high yield and excellent thermal stab...

Polyol-Based Deep Eutectic Solvents for Extraction of Natural Polyphenolic Antioxidants from Chlorella vulgaris

Due to increasing demand of natural antioxidants for pharmaceutical, food and cosmetic applications, extraction of polyphenols from natural resources has received enormous attention. In this regard, microalgae biomass exhibits great potential for target bioactive compounds accumulation. Conventionally, petroleum-derived volatile organic solvents (VOCs) and water have been used to recover polyphenols from biomass; however, VOCs are hazardous, nonenvironmentally friendly solvents while water suffers from coextraction of other impurities. Therefore, the goal of this work is to evaluate renewable deep eutectic solvents (DES) as alternative to conventional solvents for recovering polyphenols from microalgal biomass. In particular, Chlorella vulgaris was subjected to solvent extraction using 12 DES systems composed of choline chloride (ChCl) and polyols including glycerol (Gly), ethylene glycol (EG), 1,3-propanediol (PDO) and 1,4-butanediol (BDO) and two benchmark conventional solvents, namely ethyl acetate and...

Eutectic System Based on Urea and Potassium Sodium Tartrate

Deep eutectic solvents (DESs) are considered as better alternative solvents in chemical and physical processes. The binary mixture of urea and potassium sodium tartrate is explored in this study. A eutectic system is determined at composition made up of 33% potassium sodium tartrate and 67% urea (1:2 molar ratio). This eutectic system has a freezing point of 19.83 ± 0.76 °C, density of 1.1971 ± 0.0003 g mL-1, and viscosity of 34.4226 ± 0.0665 cP. The most stable conformation for the adduct of urea and potassium sodium tartrate with water molecules was determined through density functional calculations. The gas phase total energy for the adduct was determined as -5576863 kJ mol-1. Electrostatic interactions between the cations and the carboxylate sites are present, H-bonding between protons of urea and the hydroxyl oxygen of the tartrate, and intramolecular H-bonding between the hydroxyl and carboxylate sites of tartrate are accounted in the structure. The total energy associated with nonbonding interactions is computed as -826 kJ mol-1, which suggests that these interactions stabilize the formation of the DES system of potassium sodium tartrate and urea.

Catalytic oxidative desulfurization of fuels in acidic deep eutectic solvents with [(C6H13)3P(C14H29)]3PMo12O40 as a catalyst

Deep eutectic solvents (DESs) are a new class of green solvents analogous to ionic liquids due to their biodegradable capacity and low cost. However, the direct extractive desulfurization of diesel oil by DESs cannot meet the government’s standard. In this work, amphiphilic polyoxometalates were synthesized and characterized by FT-IR and mass spectrometry. The oxidative desulfurization results showed that benzothiophene (BT) could be completely removed by employing a [(C6H13)3P(C14H29)]3PMo12O40, DES (ChCl/2Ac) and H2O2 system. It was also found that the organic cation of catalysts played a positive role in oxidative desulfurization. The reaction conditions, such as reaction temperature and time, the amount of catalyst and DES and H2O2/S (O/S) molar ratio, were optimized. Different sulfides were tested to determine the desulfurization selectivity of the optimal reaction system, and it was found that 97.2% of dibenzothiophene (DBT) could be removed followed by 80.7% of 4-MDBT and 76.0% of 4,6-DMDBT. After reaction, the IR spectra showed that the catalyst [(C6H13)3P(C14H29)]3PMo12O40 was stable during the reaction process and the oxidative product was dibenzothiophene sulfone (DBTO2). Furthermore, the catalyst can be regenerated and recycled for four runs with little loss of activity.

Environmentally-Friendly Extraction of Flavonoids from Cyclocarya paliurus (Batal.) Iljinskaja Leaves with Deep Eutectic Solvents and Evaluation of Their Antioxidant Activities.

Deep eutectic solvents (DESs) are commonly employed as environmentally-friendly solvents in numerous chemical applications owing to their unique physicochemical properties. In this study, a novel and environmentally-friendly extraction method based on ultrasound assisted-deep eutectic solvent extraction (UAE-DES) was investigated for the extraction of flavonoids from Cyclocarya paliurus (Batal.) Iljinskaja (C. paliurus) leaves, and the antioxidant activities of these flavonoids were evaluated. Nine different DES systems based on either two or three components were tested, and the choline chloride/1,4–butanediol system (1:5 molar ratio) was selected as the optimal system for maximizing the flavonoid extraction yields. Other extraction conditions required to achieve the maximum flavonoid extraction yields from the leaves of C. paliurus were as follows: DES water content (v/v), 30%; extraction time, 30 min; temperature, 60 °C; and solid-liquid ratio, 20 mg/mL. Liquid chromatography-mass spectrometry allowed the detection of five flavonoids in the extract, namely kaempferol-7-O-α-l-rhamnoside, kaempferol, quercetin, quercetin-3-O-β-d-glucuronide, and kaempferol-3-O-β-d-glucuronide. In vitro antioxidant tests revealed that the flavonoid-containing extract exhibited strong DPPH and ABTS radical-scavenging abilities. Results indicate that UAE-DES is a suitable approach for the selective extraction of flavonoids from C. paliurus leaves, and DESs can be employed as sustainable extraction media for other bioactive compounds.

Micelle Structure in a Deep Eutectic Solvent for the Electrochemical Preparation of Nanomaterials.

The self-aggregation of a surfactant in a deep eutectic solvent (DES) for electrodeposition is reported. The physical properties and electrochemical behavior of an anionic surfactant, sodium dodecyl sulfate (SDS), in a widely used DES, a choline chloride-urea mixture (ChCl-urea), were investigated. On the basis of surface tension and the conductivity measurements, the SDS micelles that were formed in the ChCl-urea system remained stable at higher temperatures, that is, 90 °C. Cyclic voltammetric and chronoamperometric data indicate that the addition of SDS to the DES may alter the nucleation and the growth processes that occur in the electrodeposition process. Scanning electron microscopy images show that the SDS adsorption prevents dendrite formation during the electrodeposition process. A simple mechanism for the formation of the SDS micelles in the DES system for electrodeposition is proposed.

Synthesis and Physical and Thermodynamic Properties of Lactic Acid and Malic Acid-Based Natural Deep Eutectic Solvents

In this paper, four natural deep eutectic solvents (NADES) systems were prepared at specific molar ratios, La:Bet (2:1) (lactic acid/betaine), La:Hist (9:1) (lactic acid/histidine), Ma:Bet:H2O (1:2:3) (malic acid/betaine/water) and Ma:Bet:Pro:H2O (1:1:1:2) (malic acid/betaine/proline/water). Their physical and thermodynamic properties were studied, namely viscosity, electrical conductivity, and heat capacity. The viscosity and electrical conductivity were determined as a function of temperature and the correlation for the temperature dependence was obtained and discussed based on Arrhenius theory. The heat capacity for all eutectic systems was measured by differential scanning calorimetry (DSC) over a temperature range of 293.15–363.15 K. The ability of these NADES to reduce cellulose crystallinity was evaluated. Cellulose crystallinity after suspension in these NADES was studied by X-ray diffraction. Cellulose suspended in Ma/Bet/H2O (1:2:3) suffer the highest crystallinity reduction among the systems st...

BTPC-Based DES-Functionalized CNTs for As3+ Removal from Water: NARX Neural Network Approach

AbstractIn this study, a novel adsorbent process was developed using a deep eutectic solvent (DES) system based on benzyltriphenylphosphonium chloride (BTPC) as a functionalization agent of carbon ...

Integration of facile deep eutectic solvents pretreatment for enhanced enzymatic hydrolysis and lignin valorization from industrial xylose residue

In this study, a novel biomass pretreatment process using three kinds of deep eutectic solvents (DESs) was developed to improve saccharification efficiency and lignin valorization. The major components of xylose residue including cellulose and lignin fractions were released, recovered and utilized. Pretreatment with betaine/lactic acid system at 120 °C for 2 h was found to be the optimal conditions with prominently increased enzymatic digestibility (from 55.3% to 96.8%). The efficient conversion was mainly ascribed to the significant delignification efficiency of 81.6% after betaine/lactic acid pretreatment, which caused incompact structure and corrosive surface of treated xylose residue. The recoverable lignin had high purity, low molecular weight (630–2040 g/mol) and polydispersity (1.07–1.76). Based on the comprehensive analysis, the one-pot DESs system provides us a facile and effective approach for whole components valorization of lignocellulosic materials.

Enhanced phenolic compounds extraction from Morus alba L. leaves by deep eutectic solvents combined with ultrasonic-assisted extraction

It is of great significance to develop green solvents for promoting green and sustainable technology. Deep eutectic solvents (DESs) as new extraction solvents are emerging in the search for efficient the extraction of bioactive compounds or drugs. In this study, twelve types of DESs including choline chloride-, betaine-, and l-proline-based DESs were investigated in combination with ultrasonic-assisted extraction (UAE) for the extraction of phenolic compounds from Morus alba L. leaves. Compared with conventional extraction system, DESs composed of choline chloride/citric acid showed more effective extraction yields (22.66 mg/g vs. 15.29 mg/g). The operation conditions were also optimized systematically. In addition, liquid–liquid extraction was an effective approach to recover the major phenolic compounds in the extracts. The recovery and recyclability of DESs were also evaluated. A broad extractability of phenolic compounds in the certain designed DESs systems was observed according to principal component analysis (PCA). The developed DESs can be an alternative procedure for the green and efficient extraction of phenolic compounds from natural sources.

Effect of Ethylene, Diethylene, and Triethylene Glycols and Glycerol on the Physicochemical Properties and Phase Behavior of Benzyltrimethyl and Benzyltributylammonium Chloride Based Deep Eutectic Solvents at 283.15–343.15 K

Deep eutectic solvents (DESs) are regarded as a promising and emerging alternative for volatile organic compounds (VOCs) due to their cost-effectiveness and environmentally sustainable nature. Formulation of new DESs and thorough investigation of their physicochemical properties have been on the rise ever since potential applications of DES have been realized. The present study reports a new series of DES based on benzyltrimethylammonium chloride and benzyltributylammonium chloride as hydrogen bond acceptor (HBAs) with three ethylene glycols and glycerols as hydrogen bond donors (HBDs). The current work includes the synthesis, characterization, and investigation of the thermophysical properties of a series of DES systems. The studied properties include density, ρ, speed of sound, u, viscosity, η, refractive index, nD, and electrical conductivity, σ, for all DESs in the temperature range from 283.15 to 343.15 K. The observed trends in properties like density, speed of sound, viscosity, and refractive indic...