Deep Eutectic Solvent System Research Articles

Novel working fluid pair of methanol/betaine-urea for absorption refrigeration system driven by low-temperature heat sources

An absorption refrigeration system (ARS) designed for low-temperature heat sources like industrial waste heat, solar-heated water, or geothermal heat can offer substantial energy-saving benefits. This study explores a novel working fluid pair comprising methanol and betaine-urea (BE-UR), forming a deep eutectic solvent (DES) system. This design capitalizes on methanol's high enthalpy of vaporization, the low heat capacity of the working pair, and the appropriate intensity and strength of the hydrogen bonding network within the solution. The proposed fluid pair shows full solubility of BE-UR in methanol at a mole ratio of 1.81 to 1 (methanol to BE-UR), with an equilibrium vapor pressure dropping to 8.59 kPa at 303.15 K. Molecular dynamics simulations unveil a microscale solution structure, showcasing a hydrogen bond network and unbonded methanol in the concentrated working fluid pair. This configuration enhances the absorption process of methanol vapor in the ARS absorption unit. Aspen Plus simulations predict a coefficient of performance (COP) exceeding 0.85, comparable to H2O/LiBr in single effect-ARS and outperforming NH3/H2O in SE-ARS by approximately 30 %, while maintaining a lower cycle ratio of about 2.

Development of deep eutectic solvent systems and their formulation: Assessment of solubilization potential on poorly water-soluble drugs

Development of deep eutectic solvent systems and their formulation: Assessment of solubilization potential on poorly water-soluble drugs

Efficient extraction of lignin from moso bamboo by microwave-assisted ternary deep eutectic solvent pretreatment for enhanced enzymatic hydrolysis

Applications of deep eutectic solvent (DES) systems to separate lignocellulosic components are of interest to develop environmentally friendly processes and achieve efficient utilization of biomass. To enhance the performance of a binary neutral DES (glycerol:guanidine hydrochloride), various Lewis acids (e.g., AlCl3·6H2O, FeCl3·6H2O, etc.) were introduced to synthesize a series of ternary DES systems; these were coupled with microwave heating and applied to moso bamboo. Among the ternary DES systems evaluated, the FeCl3-based DES effectively removed lignin (81.17%) and xylan (85.42%), significantly improving enzymatic digestibility of the residual glucan and xylan (90.15% and 99.51%, respectively). Furthermore, 50.74% of the lignin, with high purity and a well-preserved structure, was recovered. A recyclability experiment showed that the pretreatment performance of the FeCl3-based DES was still basically maintained after five cycles. Overall, the microwave-assisted ternary DES pretreatment approach proposed in this study appears to be a promising option for sustainable biorefinery operations.

Balancing the pretreatment effect of deep eutectic solvents on biomass and the activity of β-glucosidase originating from Paenibacillus sp. LLZ1

The two major impediments to biomass resourcing are the catalytic efficiency of enzymes and the effectiveness of biomass pretreatment. In this study, six genes encoding β-Glucosidases (BGLs) derived from Paenibacillus sp. LLZ1 were cloned and expressed. The activity of BGL-F, which had the highest enzyme activity, was 24.1 U/mg, which was 39.8–83.7% higher than that of the other BGLs. Molecular docking and surface charge analyses showed that the binding energy of BGL-F to cellobiose and its electronegative ligand-binding pocket were greater than those of other BGLs. On the other hand, by calculating and comparing the Kamlet–Taft (KT) values of deep eutectic solvent (DES) composed of different hydrogen bond donors (HBD) and hydrogen bond acceptors (HDA), it was found that DES composed of betaine and glycerol had the highest α value of 0.97, meaning that it could provide the highest hydrogen bonding capacity, and thus it had the best pretreatment effect on biomass. Analysis by circular dichroism (CD) spectroscopy revealed a decrease in α-helix and an increase in β-strand in the secondary structure of the DES-treated BGL-F, implying an increase in enzyme activity and stability. This result was also confirmed experimentally by the fact that the Km and Vmax of the enzyme in the DES system increased by 13.2% and 57.9%, respectively, and the inactivation rate (kd) decreased by 21.4%. The results of this study showed that DES consisting of glycerol-betaine achieved a better balance between the promotion of enzyme activity and biomass pretreatment.

In-situ fibrillated sugarcane cell wall decorated with WO3-Ag nanocatalyst for efficient adsorption-photocatalytic removal of antibiotics from water

Lignocellulose nanomaterials are extremely compelling in the remediation of organic wastewater, yet still present challenges regarding cost-efficiency, manufacturability, and scalability. Instead of a conventional bottom-up engineering, this study top-down designs multiporous, high specific surface area and anisotropic quaternized lignocellulose nano-sponge, based on the effectiveness of reactive deep eutectic solvent system on in-situ fibrillating sugarcane cell walls. The as-prepared sugarcane sponge reveals outstanding adsorption abilities for broad-spectrum antibiotics via a combination of intermolecular and electrostatic interactions, and serves as a desired carrier for hybrid nano-catalysts (e.g. WO3-Ag) with enhanced overall quantum efficiency. The developed sugarcane/WO3/Ag sponge integrating a functionality of adsorption enrichment with visible-light photocatalysis, can efficiently remove ∼ 99 % tetracycline/levofloxacin/norfloxacin at an initial concentration of 20 mg/L within 120 min at pH 7. The degradation pathway of antibiotics is inferred from the identified intermediates and primary active species. Additionally, the favorable mechanical strength, water stability and reusability of sugarcane/WO3/Ag sponge are demonstrated, which originate from the well-organized lignocellulose fibrils in in-situ fibrillated sugarcane cell wall and their intensive interactions with anchored nanoparticles. Our study offers a novel and feasible top-down nanostructure engineering strategy to manufacture high-performance lignocellulose-based nanocomposites towards environmental remediation.

A tailored deep eutectic solvent for high-yield conversion of poplar residues to bio-based building blocks at mild conditions

The generation of condensed compounds in a deep eutectic solvent (DES) pretreatment has become a paramount factor that inhibits the further conversion of pretreated cellulose-rich substrate. This study proposed a novel three-constituent DES system for the value-added utilization of poplar residues by efficiently suppressing hemicellulose derived condensation reactions. The results showed that adding ethanol into the DES system could effectively deconstruct the recalcitrant structure of poplar residues, simultaneously hindering the condensed composition formation. Under optimum ethanol addition (30%), the maximum xylan and lignin removal of 87.94% and 90.99% could be achieved, with more than 90.47% of glucan being preserved. With this, the glucan enzymatic hydrolysis efficiency was remarkably improved to 100% under the pretreatment conditions of 100 °C for 60 min, which was 84.69 times higher than the regular DES-pretreated poplar residues (1.17%). The working mechanism of relieving condensation reactions was characterized by Py-GC–MS, NMR, SEM, FTIR, and others. The results demonstrated that the addition of ethanol could regulate the degradation/conversion pathway of hemicellulose and lignin precipitation, thus inhibit the formation of condensed compounds during the pretreatment.

Simultaneous and selective extraction of different polarity bioactive substances from Ligustri Lucidi Fructus based on a designable biphasic deep eutectic solvent

Most plants contain hydrophilic and hydrophobic bioactive compounds, traditional organic solvent extraction processes can often only extract one of the components, resulting in a cumbersome process and a waste of resources. To make full use of the active resources in Ligustri Lucidi Fructus, a biphasic deep eutectic solvent (DES) system was established. By adjusting the polarity, oleanolic acid (OA) and ursolic acid (UA) were enriched in the hydrophobic phase, and flavonoids and procyanidine (PAC) in the hydrophilic phase, respectively. Established with a 1:1 vol ratio of hydrophobic DES MIA (DL-menthol: isopropyl alcohol, 1:1) and hydrophilic DES CBE (choline chloride: betaine: ethylene glycol, 1:1:2). The biphasic system had the highest extraction rate. The response surface method was used to further optimize the extraction conditions. After optimization, the extraction yields of OA and UA were 10.96 ± 0.35 mg/g and 11.67 ± 0.26 mg/g in the MIA phase, and the extracted yields of flavonoids and PAC in the CBE phase were 77.38 ± 0.62 mg/g and 5.20 ± 0.03 mg/g, respectively. Compared with the conventional single-phase extraction with organic solvents, the biphasic system provided higher extraction rate and selectivity and the extracts showed stronger antioxidant activity. Compared to the single-phase extraction utilizing conventional organic solvents, the results demonstrated significant improvement. Consequently, by adjusting the polarity of the biphasic DES system, this study supplies an argument for increasing the extraction efficiency of plant resources. This expands the application of the biphasic DES system and contributes to the high-value exploitation of natural commodities.

Designing Low Toxic Deep Eutectic Solvents for the Green Recycle of Lithium-Ion Batteries Cathodes.

The Lithium-ion battery (LIB) is one of the main energy storage equipment. Its cathode material contains Li, Co, and other valuable metals. Therefore, recycling spent LIBs can reduce environmental pollution and resource waste, which is significant for sustainable development. However, traditional metallurgical methods are not environmentally friendly, with high cost and environmental toxicity. Recently, the concept of green chemistry gives rise to environmental and efficient recycling technology, which promotes the transition of recycling solvents from organic solvents to green solvents represented by deep eutectic solvents (DESs). DESs are considered as ideal alternative solvents in extraction processes, attracting great attention due to their low cost, low toxicity, good biodegradability, and high extraction capacity. It is very important to develop the DESs system for LIBs recycling for sustainable development of energy and green economic development of recycling technology. In this work, the applications and research progress of DESs in LIBs recovery are reviewed, and the physicochemical properties such as viscosity, toxicity and regulatory properties are summarized and discussed. In particular, the toxicity data of DESs are collected and analyzed. Finally, the guidance and prospects for future research are put forward, aiming to explore more suitable DESs for recycling valuable metals in batteries.

Deep Eutectic Solvents as Agents for Improving the Solubility of Edaravone: Experimental and Theoretical Considerations.

In this study, both practical and theoretical aspects of the solubility of edaravone (EDA) in Deep Eutectic Solvents (DESs) were considered. The solubility of edaravone in some media, including water, can be limited, which creates the need for new efficient and environmentally safe solvents. The solubility of EDA was measured spectrophotometrically and the complex intermolecular interactions within the systems were studied with the COSMO-RS framework. Of the four studied DES systems, three outperformed the most efficient classical organic solvent, namely dichloromethane, with the DES comprising choline chloride and triethylene glycol, acting as hydrogen bond donor (HBD), in a 1:2 molar proportion yielding the highest solubility of EDA. Interestingly, the addition of a specific amount of water further increased EDA solubility. Theoretical analysis revealed that in pure water or solutions with high water content, EDA stacking is responsible for self-aggregation and lower solubility. On the other hand, the presence of HBDs leads to the formation of intermolecular clusters with EDA, reducing self-aggregation. However, in the presence of a stoichiometric amount of water, a three-molecular EDA-HBD-water complex is formed, which explains why water can also act as a co-solvent. The high probability of formation of this type of complexes is related to the high affinity of the components, which exceeds all other possible complexes.

Improving saccharification efficiency of corn stover through ferric chloride-deep eutectic solvent pretreatment

An effective deep eutectic solvent (DES) and Iron(III) chloride (FeCl3) combination pretreatment system was developed to improve the removal efficiency of lignin and hemicellulose from corn stover (CS) and enhance its saccharification. N-(2-hydroxyethyl)ethylenediamine (NE) was selected as the hydrogen-bond-donor for preparing ChCl-based DES (ChCl:NE), and a mixture of ChCl:NE (60 wt%) and FeCl3 (0.5 wt%) was utilized for combination pretreatment of CS at 110 ℃ for 50 min. FeCl3/ChCl:NE effectively removed lignin (87.0 %) and xylan (55.9 %) and the enzymatic hydrolysis activity of FeCl3/ChCl:NE-treated CS was 5.5 times that of CS. The reducing sugar yield of pretreated CS was 98.6 %. FeCl3/ChCl:NE significantly disrupted the crystal structure of cellulose in CS and improved the removal of lignin and hemicellulose, enhancing the conversion of cellulose and hemicellulose into monomeric sugars. Overall, this combination of FeCl3 and DES pretreatment methods has high application potential for the biological refining of lignocellulose.

Pretreatment of shrimp shells with an acidic deep eutectic solvent system for chitin extraction and its enhanced performance as a carrier for immobilized lipase

Existing methods for chitin extraction usually produce substantial waste, which poses ecological hazards. Natural deep eutectic solvent (NADES) offers a promising one-step pretreatment alternative, replacing the resource-intensive demineralization (DM) and deproteinization (DP) process. Hence, in this study, the influence of various acidic NADES, on achieving a simplified one-step DM and DP in the chitin extraction process was investigated. The study yielded chitin with 87.73 % purity, and microstructural analysis showed that NADES pretreatment minimally affected chitin quality without deacetylation. In addition, chitin extracted using choline chloride-oxalic acid as a carrier displayed excellent performance in the immobilization of Geobacillus thermocatenulatus lipase 2 (GTL2) because of obvious Ca2+ activation effect. This process contributed to enhancement of immobilized enzyme activity. The immobilized GTL2 showed excellent hydrolytic capabilities, with its highest activity reaching 547.80 ± 20.62 U/mg, significantly better than the five commercial lipases that exhibited <40 % of the enzyme activity. Furthermore, the hydrolytic capacity of immobilized GTL2 was notably high for 4-nitrophenyl butyrate, measuring 935.47 ± 51.60 U/mg. This study provided a constructive approach for the one-step pretreatment of shrimp shells with organic acid-based NADES to isolate and purify chitin and its potential application as an immobilized carrier to enhance enzyme activity.

Effect of glucose–citric acid deep eutectic solvent on the vapor–liquid equilibrium of an aqueous ethanol solution

Objectives. To study the effect of a deep eutectic solvent (DES) based on glucose and citric acid on the vapor–liquid equilibrium of an aqueous solution of ethanol.Methods. A qualitative and quantitative analysis of the conditions of vapor–liquid equilibrium in an ethanol–water–DES ternary mixture was performed based on the open evaporation method and the measurement of TPxy data using a Świętosławski ebulliometer. Since the volatility of the DES is negligible in comparison with that of water and ethanol, the composition of the vapor phase was measured by means of Karl Fischer titration. The conditions of vapor–liquid phase equilibrium were modeled using the UNIFAC model.Results. The open evaporation method was used to determine the curves of residual concentrations for the ethanol–water–DES mixture at various DES concentrations and compositions (glucose–citric acid ratios). TPxy data was obtained for the mixture produced by adding 30 wt % DES to an aqueous solution of ethanol at atmospheric pressure. Studies show that DES based on glucose and citric acid has a significant effect on the relative volatility of ethanol in aqueous solution, leading to the disappearance of the azeotropic point. This effect is due to only the presence of glucose. Citric acid does not change the composition of the equilibrium phases, but rather increases the solubility of glucose in aqueous ethanol solutions. This is especially important at high ethanol concentrations, since glucose is poorly soluble in ethanol.Conclusions. Addition of DES based on glucose and citric acid to an aqueous solution of ethanol leads to the disappearance of the azeotropic point. DES can thus be considered as a promising entrainer for extracting ethanol from aqueous solutions using extractive distillation. Modeling of the conditions of vapor–liquid equilibrium in the ethanol–water–DES system using the UNIFAC model showed a satisfactory level of accuracy. The error in the calculated data increases with increasing the glucose concentration, while remaining acceptable for practical use.

Self-Healing and Wide Temperature-Tolerant Cellulose-Based Eutectogels for Reversible Humidity Detection.

A kind of ionic conductive gel (also named eutectogel) is developed from an inorganic salt (ZnCl2)-based deep eutectic solvent (DES). The ternary DES consists of ZnCl2, acrylic acid, and water, and cotton linter cellulose is introduced into the DES system to tailor its mechanical and conductive properties. Enabled by the extensive hydrogen bonds and ion-dipole interactions, the obtained eutectogel displays superior ionic conductivity (0.33 S/m), high stretchability (up to 2050%), large tensile strength (1.82 MPa), and wide temperature tolerance (-40 to 60 °C). In particular, the water-induced coordination interactions can tune the strength of hydrogen/ionic bonds in the eutectogels, imparting them with appealing humidity sensing ability in complex and extreme conditions.

Preparation of a nickel-cobalt-zinc alloy coating as SOFC connection material in deep eutectic solvent

The Ni-Co-Zn alloy coating is prepared in a deep eutectic solvent system using pulse power supply technology, and the feasibility of the deep eutectic solvent system as an electrolyte is confirmed through infrared spectroscopy and cyclic voltammetry. The microscopic morphology analysis shows that the plating layer is uniform and dense, and the grains are spherical particles, and it is detected that the oxidized weight gain rate of the plating layer is 7.6842 × 10−8 g2 cm−4·h−1 at 900 °C, which is 3 orders of magnitude different from the oxidation rate constant of the substrate. The corrosion potential increases to −0.281 V in 3.5 % NaCl solution, and the corrosion current density decreases to 3.259 × 10−7 (A/cm2), with an ASR of 43.64 mΩ cm2 at 800 °C. The results indicate that the Ni-Co-Zn coating can meet the requirements for an SOFC connector material.

Harnessing deep eutectic solvents for upcycling waste membranes into high-performance adsorbents and energy storage materials

Polymer membranes waste management across the globe is a great concern due to the lack of advancement in upcycling methods. Herein, waste polysulfone (W-PSF) membranes, an emerging environment threat, have been converted to multi-functional carbon materials via green method using choline chloride:FeCl3 (CC:FeCl3) based deep eutectic solvent (DES) systems through solvothermal reaction followed by pyrolysis at 900 °C. The optimized material (Fe-WPSF-01) showed excellent adsorption capacity towards Malachite green (MG), Congo red (CR), Amoxicillin (Amo), and Bisphenol-A (BPA) with 515, 407, 216, and 322 mg/g of adsorption capacity, as calculated from the well-fitted Langmuir isotherm. Further, an easy-to-use adsorptive membrane filtration method was established to investigate the robustness of Fe-WPSF-01 in removing the above pollutants in continuous flow method. The resultant flux rate was 700–815 L.m−2.h−1 with rejection rates of 99, 98, 92, & 98 % for MG, CR, Amo, & BPA, respectively. Besides, the material showed recyclability for up to 10 cycles with 92.1 & 81.2 % of rejection rates for MG and Amo. After the potential usage of carbon material in adsorption studies, secondary materials were again pyrolyzed to use as an electrode in supercapacitors with a specific capacitance of 215 F/g at a current density of 0.1 A/g. Electrode showed capacity retention of 97.51 % even after about 20,000 cycles at an increased current density of about 5 A/g. Thus, a potential sustainable approach of upcycling the W-PSF membranes for energy and environmental applications are well-presented in this work.

Investigation on improvement of enantioseparation based on clindamycin phosphate by chiral deep eutectic solvents in capillary electrophoresis.

In this work, the potential synergetic effect between deep eutectic solvents and an antibiotic chiral selector (clindamycin phosphate) for enantioseparation was investigated in capillary electrophoresis. We synthesized a series of deep eutectic solvents with choline chloride as hydrogen bond acceptor and three α-hydroxyl acids (l-lactic acid, l-malic acid, and l-tartaric acid) as hydrogen bond donors. Compared to the single clindamycin phosphate separation system, significantly improved separations of model drugs were observed in several synergetic systems. Compared to deep eutectic solvents with a single hydrogen bond donor, deep eutectic solvents with mixed-type hydrogen bond donors were superior. The influences of several key parameters including the type and proportion of organic modifier, clindamycin phosphate concentrations, deep eutectic solvents concentrations, and buffer pH were investigated in detail. The mechanism of the enhanced separations in deep eutectic solvents systems was investigated by means of electroosmotic flow analysis, nuclear magnetic resonance analysis, and molecular modeling. It was the first time that the synergetic systems between deep eutectic solvents and antibiotic chiral selector were established in capillary electrophoresis, and these deep eutectic solvents were demonstrated to have a good synergetic effect with clindamycin phosphate for enantioseparation.

Evaluation of deep eutectic solvents chiral selectors based on lactobionic acid in capillary electrophoresis.

Recently, deep eutectic solvents (DESs) have attracted considerable interest in analytical chemistry. This work described the enantioseparations of twenty amino alcohol drugs with several DESs based on lactobionic acid (LA) as the sole chiral selector in capillary electrophoresis (CE) firstly. Compared to the single LA system and the ionic liquid/LA synergistic system, the DES system exhibited considerably improved separations. The influences of some key parameters on separations were investigated in detail. This work also experimentally demonstrated that the carboxyl group was indispensable in the process of chiral recognition. The mechanisms of the improvements of DESs on enantioseparations were studied via ultraviolet spectroscopy. Furthermore, the proposed method was used to determine the enantiomeric purity of propranolol hydrochloride successfully. This is the first time that chiral DESs were utilized as the sole chiral selectors in CE, and this strategy has opened up a new prospect for the use of DESs in enantioseparation.

The Pitfalls of Deep Eutectic Solvents in the Recycling of Lithium‐Ion Batteries

The exponentially increasing demand for lithium‐ion batteries and their limited lifetime lead to a significant increase in spent batteries. With the goal to address the sustainability and recyclability to minimize negative effects for the environment, an efficient process is vital to recover valuable materials from spent batteries by recycling. In this regard, deep eutectic solvents (DESs) have attracted huge interest, due to their unique ability to efficiently extract valuable metals from spent batteries, while also being rendered greener and more cost‐effective compared to current pyrometallurgy and/or hydrometallurgy. However, the DES approach also has its own set of challenges and drawbacks, which hinder the widespread use in the industry, including its restricted recyclability, high viscosity, low thermal and chemical stability, complex chemistry, as well as limited scalability. In this perspective, it is claimed that ongoing future research on the recycling of lithium‐ion batteries requires the exploration of alternative processes including modification of current hydrometallurgy processes, if the consistent improvements cannot be achieved in DES system for recycling valuable elements.

Study of ternary deep eutectic solvents to enhance the bending properties of ash wood.

Deep eutectic solvents (DESs) are considered one of the most promising biomass pretreatment reagents, and their research applications in woody fibrous biomass are increasing yearly. Inspired by the research related to wood bending, we explored the effects of different DES systems on the bending development of wood, and the results showed that the addition of anhydrous ferric trichloride to the DES system of lactic acid/choline chloride could enhance the treatment effect that increased the bendability and torsion resistance of ash wood. The anhydrous FeCl3 could act as an active site and provide acidic protons to improve the treatment efficiency of DES. In addition, the addition of an appropriate amount of water can reduce the viscosity of the DES system, and the highest lignin removal rate was obtained at 10 wt% of water in the DES, which resulted in the best mechanical properties and tensile resilience of ash wood, with the tensile strength and stability of 97 MPa and 13.6%, respectively, as determined by experiments with different water contents in different mass fractions. Therefore, using a DES can effectively improve the bending properties of wood.

Multiscale regulation of S, N, O tri-doped carbon/Co8FeS8 catalysts with SO42−-riched and lattice distortion for efficient water splitting

The multiscale regulation of heteroatom configuration, lattice defects and SO42− was realized by deep eutectic solvent system. The catalytic performance of the catalyst with multi-scale regulation is significantly improved. The regulation mechanism of C and SO42− on metal sites was revealed.