Application Of Deep Eutectic Solvents Research Articles

Deep eutectic solvents as reusable catalysts and promoter for the greener syntheses of small molecules: Recent advances

Deep eutectic solvents (DESs) are significant environmentally benign media in the field of green chemistry. They are known not only for their inexpensive nature, biodegradability, non-toxicity, and bioavailability, but also for recyclability and their ease of preparation and purification. DESs are made up of hydrogen bond donor substituents (such as urea, carboxylic acid, glycerol, metals, etc.) and hydrogen bond acceptor substituents such as halide salts; they have a lower melting point than each substituent comprising the mixture. DESs find applications in biotransformation, gas separation, biomass valorization, electrochemistry, extraction, and dissolution process as well as in material chemistry and other assorted fields of chemistry. Interestingly, DESs fulfil a unique dual role as green solvents, promoters and catalysts in organic syntheses. Thus, it is noteworthy that chemical progresses and transformation with external catalysts in cross-coupling reactions, oxidations and reductions are not covered in this overview. This review mostly focuses on leading-edge applications of DES as a reusable catalyst in the expeditious synthesis of assorted small molecules central in the assembly of broad-spectrum pharmaceuticals, and total synthesis of common natural products.

Development and applications of deep eutectic solvents in different chromatographic techniques

Development and applications of deep eutectic solvents in different chromatographic techniques

Applications of Deep Eutectic Solvents in Sample Preparation and Extraction of Organic Molecules.

The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this review, the focus will be on the usage of DES in extracting a substantial variety of organic compounds from different sample matrices, which not only exhibit great results but surpass the analytical performance of conventional solvents. Moreover, the properties of the most commonly used DES will be summarized.

CO2 absorption performance of ChCl-MEA deep eutectic solvent in microchannel

Deep eutectic solvent (DES) has been a new type of absorbent for CO2 capture due to the advantages of environmental friendliness, simple synthesis and excellent selectivity. A series of choline chloride (ChCl)-monoethanolamine (MEA) deep eutectic solvents with various water contents were prepared. The effects of gas-liquid flow rate, molar ratio of ChCl-MEA, water content and temperature on CO2 absorption performance and mass transfer were investigated. The addition of an appropriate amount of water can effectively reduce the viscosity of DES and improve its CO2 capture ability. The results show that the CO2 absorption efficiency, absorption rate, loading and mass transfer coefficient of ChCl-MEA deep eutectic solvent are optimal when the water content is 70 wt% for the DES with the molar ratio of ChCl and MEA 1:6. When the water content exceeds 70 wt%, the hydrogen bond network of DES would be destroyed, and its CO2 capture ability would be weakened. According to the Arrhenius equation, the reaction activation energy of CO2 absorption is as low as 7.54 kJ·mol−1 when the water content is 70 wt% in DES with the molar ratio of ChCl and MEA 1:6. This study can provide technical support for the application of deep eutectic solvents in CO2 capture.

The application of deep eutectic solvents in lithium-ion battery recycling: A comprehensive review

The extensive use of lithium-ion batteries (LIBs) in new electric vehicles has effectively alleviated the problems of insufficient oil and gas resources and environmental pollution. It is of great significance to realize the goals of "carbon neutrality" and "carbon peaking." As the key and last link in the use of power batteries, recycling waste LIBs is conducive to realizing resource return and avoiding pollution and potential risks of toxic and harmful substances in the environment. With the efforts of many researchers, the harmless treatment and resource recovery process of spent LIBs has been maturing. In recent years, some new recycling processes have appeared frequently to solve the problems of high energy consumption and secondary pollution in the traditional approach. Among these new technologies, green and inexpensive deep-eutectic solvents (DESs) have been particularly attractive due to their excellent selectivity and leaching efficiency. This review summarizes the dissolution mechanism of valuable metals from LIB cathode materials using DESs. At the same time, the advantages and challenges faced by DESs in cathode material recycling were analyzed, and an outlook was presented for the future development of DESs in the field of battery recycling.

Structure–properties relationships of deep eutectic solvents formed between choline chloride and carboxylic acids: Experimental and computational study

To implement different applications of deep eutectic solvents (DESs), the knowledge of their structure and properties should be enhanced. In this work, experimental characterizations together with theoretical calculations were employed to study the structure–properties relationships of seven ChCl-carboxylic acids DESs. The obtained DESs were analyzed using NMR spectroscopy to check their structures and interactions. The physicochemical properties of DESs, such as viscosity, conductivity, and Kamlet-Taft solvatochromic parameters, are closely related to the structure of carboxylic acids. A DES with more hydroxyl or carboxyl groups has a greater viscosity and a lower conductivity. Increasing the carbon chain of carboxylic acid reduces the polarity of the corresponding DES. Moreover, the calculation results from density functional theory (DFT) indicate that the type and intensity of intermolecular interaction of DESs are closely related to the structure of the carboxylic acid, which are consistent with experimental results. The systematic research on the structure–properties relationships expand our knowledge on the rational design of task-specific DESs.

Antimycobacterial Activity of Rosmarinus officinalis (Rosemary) Extracted by Deep Eutectic Solvents

Tuberculosis (TB) is a massive problem for public health and is the leading cause of illness and death worldwide. Rosemary (Rosmarinus officinalis) is used traditionally to treat many diseases, such as infections of the lungs including pulmonary TB. R. officinalis was collected from Al Anbar Governorate, Iraq, and was extracted with deep eutectic solvents (DESs) of many different kinds and with conventional water solvent. The antimycobacterial activities of the R. officinalis extracts were tested against multidrug-resistant (MDR) Mycobacterium tuberculosis by agar disc diffusion assay. Minimum inhibitory concentrations were measured spectrophotometrically at 570 nm. Then, a time-kill assay and cell membrane integrity analysis were conducted to investigate the effects of the most active extracts on cell growth. The in vitro cytotoxicity of the most active extracts was evaluated against Rat Embryonic Fibroblasts (REF) cell line by MTT assay. Liquid chromatography-mass spectrometry (LC-MS) was conducted to analyze the chemical components of the most active extracts. At 200 mg/mL concentration, a significant inhibition activity was seen in DES2: Tailor (DIZ = 17.33 ± 1.15 mm), followed by DES3: ChGl, DES1: LGH and DES4: ChXl. The best result was DES2: Tailor, which had a MIC of 3.12 mg/mL and an MBC of 12.5 mg/mL. The DES2 extract exhibited a high drop in the number of colonies over time, killing more than 80 colonies. The main phytochemical compounds of the R. officinalis extract were camphene, camphenilol, α-pinene, limonene, apigenin, camphor, carnosol, linalool and myrcene. R. officinalis extracts obtained by DESs have shown evident power in treating tuberculosis, and extraction by DES is a greener procedure than the methods involving conventional extraction solvents. As a result, additional research into the application of DES should be considered.

Application of deep eutectic solvents in protein extraction and purification.

Deep eutectic solvents (DESs) are a mixture of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) molecules that can consist, respectively, of natural plant metabolites such as sugars, carboxylic acids, amino acids, and ionic molecules, which are for the vast majority ammonium salts. Media such as DESs are modular tools of sustainability that can be pointed toward the extraction of bioactive molecules due to their excellent physicochemical properties, their relatively low price, and accessibility. The present review focuses on the application of DESs for protein extraction and purification. The in-depth effects and principles that apply to DES-mediated extraction using various renewable biomasses will be discussed as well. One of the most important observations being made is that DESs have a clear ability to maintain the biological and/or functional activity of the extracted proteins, as well as increase their stability compared to traditional solvents. They demonstrate true potential for a reproducible but more importantly, scalable protein extraction and purification compared to traditional methods while enabling waste valorization in some particular cases.

Recovery of rare earth elements from coal flyash using deep eutectic solvents as leachants and precipitating as oxalate or fluoride

This paper presents results of the study on the applicability of deep eutectic solvents (DES) for the recovery of rare earth elements (REE) from coal flyash (CFA) assaying REE 0.22%. The combination of DES used was choline chloride (ChCl) with lactic acid (LA) and ChCl with para toluene sulphonic acid monohydrate (pTSA). Besides the synthesis and characterisation of the DES systems, detailed study on their flow behaviour as a function of temperature and viscosity was also made. Screening studies indicated better leaching performance when the molar ratio of ChCl:pTSA and ChCl:LA were 1:1 and 1:2 respectively. Influence of various process parameters like temperature, solid to liquid ratio, reaction time and dilution ratio of DES with water on the leaching efficiency of REE and other impurity ions was investigated using the best molar ratio combination identified for the two systems. Performance of the DES systems were compared with that of individual hydrogen bond donors (HBD) namely, LA and pTSA, hydrogen bond acceptor (HBA) viz. ChCl as well as with H2SO4. The dissolved REE from the DES medium were selectively and quantitatively recovered by chemical precipitation. The DES systems gave REE leachability of about 85–95%. The mixture of ChCl:pTSA(1:1) showed higher leach recovery and faster kinetics compared to ChCl:LA(1:2). Both DES systems gave a decisive 5–8% higher leachability than the individual HBDs (LA and pTSA) and HBA (ChCl) which constitute the respective eutectic. Comparison of leaching performance of REE using DES with that of H2SO4 indicated significant enhancement, about 35%, with the former over the inorganic acid. A probable leaching mechanism of REE with the DES used is also proposed. Precipitation of REE from the DES medium was near complete with oxalic acid and NaF reagents.

Decomposition of Deep Eutectic Solvent Aids Metals Extraction in Lithium-Ion Batteries Recycling.

The application of deep eutectic solvents (DESs) to dissolve metal oxides in lithium-ion batteries (LIBs) recycling represents a green technological alternative to the mineral acids employed in hydrometallurgical recycling processes. However, DESs are much more expensive than mineral acids and must be reused to ensure economic feasibility of LIB recycling. To evaluate DES reusability, the role of the choline chloride-ethylene glycol DES decomposition products on metal oxides dissolution was investigated. The temperatures generally applied to carry on this DES leaching induced the formation of decomposition products that ultimately improved the ability to dissolve LIB metal oxides. The characterization of DES decomposition products revealed that the improved metal dissolution was mainly determined by the formation of Cl3 - , which was proposed to play a pivotal role in the oxidative dissolution of LIB metal oxides.

Applicability of Deep Eutectic Solvents in Oil and Gas Processing Fields for CO2 Control

AbstractAnthropogenic greenhouse gas emissions, particularly CO2 emissions, have grown substantially, posing environmental challenges that affect mankind and ecosystems. As a possible consequence, carbon capture and storage is a viable solution to this worldwide problem. However, some aqueous solvents have been applied to capture greenhouse gases, though they are not environmentally benign. Deep eutectic solvents (DESs) emerged as a unique choice according to research into greener solvents for this activity. The applications of DESs and the gas solubility of various DESs with emphasis on CO2 solubility in the oil and gas field are evaluated. This innovative solvent is also described in terms of its preparation and chemical composition. Detailed literature on investigation of CO2 solubility in DESs based on experimental data is included.

Molecular mechanism of waste polyethylene terephthalate recycling by the 1,5,7-triazabicyclo[4.4.0]decium acetate/ zinc acetate deep eutectic solvent: The crucial role of 1,5,7-triazabicyclo[4.4.0]decium cation

The application of deep eutectic solvents (DESs) in the catalytic degradation of polyethylene terephthalate (PET) has attracted increasing attention due to the high efficiency, biodegradability, and low toxicity of DESs. However, the relationship between the structure and activity of DESs is still ambiguous. Herein, we report an efficient 1,5,7-triazabicyclo[4.4.0]decium acetate/zinc acetate (HTBD-OAc/Zn(OAc)2) DES catalyst for recycling waste PET based on a combination of experimental and theoretical studies. First, the HTBD-OAc/ Zn(OAc)2 DES structure, in which the HTBD-OAc moiety and Zn(OAc)2 were connected through a N-H---O hydrogen bonding interaction, was clearly determined through theoretical calculations and experimental verification. Then, the HTBD-OAc/Zn(OAc)2 was found to be effective for waste PET glycolysis, where the PET conversion reached 100%, and the bis(hydroxyalkyl) terephthalate (BHET) yield reached 88.5% at 190 °C within 40 min in atmosphere. Additionally, the catalyst had high reuse performance; BHET yield remained 84.6% after the catalyst was used for over seven cycles. Density functional theory (DFT) calculations demonstrated that the PET glycolysis reaction mediated by the HTBD-OAc/Zn(OAc)2 DES included two stages, and the 1,5,7-triazabicyclo[4.4.0]decium cation (HTBD) played a crucial role. In the first stage, the active species [Zn]-OCH2CH2OH anion was generated through proton transfer from HTBD to OAc-, which was followed by HOCH2CH2O-H bond activation through the cooperation of HTBD and Zn. In the second stage, catalytic depolymerization of PET occurred through the cooperative functions of the Zn center and HOCH2CH2O- anion ligand.

Hydrophobic deep eutectic solvents as pseudo-stationary phases in capillary electrokinetic chromatography: An explorative study

Research into the application of deep eutectic solvents (DESs) in capillary electrophoresis (CE) is still in its infancy. Even so, a controversy has already arisen over the “true role” of DESs in CE. This is because the DESs employed previously were all hydrophilic, and it is therefore reasonable to speculate that they may be virtually completely dissociated into its initial components (hydrogen-bond acceptor (HBA) and hydrogen-bond donor (HBD)) in aqueous CE buffers. Since there seems to be no essential difference in CE performance between adding a DES and adding its two constituents separately (HBA and HBD) in a running buffer, the significance of using DESs in these CE systems has not been clearly established. In this context, this study established the first DES-based CE system in which a DES really worked as a single entity. To achieve this goal a hydrophobic DES (HDES), (−)-menthol:octanoic acid, was employed to act as a pseudo-stationary phase (PSP) in electrokinetic chromatography (EKC) mode. We found that the HDES is capable of forming stable aggregates (micro-droplets) which can act as a PSP in the running buffer. The novel HDES-type PSP exhibited impressive selectivities toward several groups of analogues, homologues, and isomers via hydrophobic mechanism. It can be used either solely for direct EKC separation, or in combination with traditional PSPs (e.g., cyclodextrins). As a proof-of-concept study, we have demonstrated that the synergistic effect generated in an “HDES + Hydroxypropyl-γ-cyclodextrin” dual-PSP system allowed an excellent separation of a simulated complex mixture consisting of 13 aromatic acids.

Solubilities and Transport Properties of CO2, Oxalic Acid, and Formic Acid in Mixed Solvents Composed of Deep Eutectic Solvents, Methanol, and Propylene Carbonate.

Recently, deep eutectic solvents (DES) have been considered as possible electrolytes for the electrochemical reduction of CO2 to value-added products such as formic and oxalic acids. The applicability of pure DES as electrolytes is hindered by high viscosities. Mixtures of DES with organic solvents can be a promising way of designing superior electrolytes by exploiting the advantages of each solvent type. In this study, densities, viscosities, diffusivities, and ionic conductivities of mixed solvents comprising DES (i.e., reline and ethaline), methanol, and propylene carbonate were computed using molecular simulations. To provide a quantitative assessment of the affinity and mass transport of CO2 and oxalic and formic acids in the mixed solvents, the solubilities and self-diffusivities of these solutes were also computed. Our results show that the addition of DES to the organic solvents enhances the solubilities of oxalic and formic acids, while the solubility of CO2 in the ethaline-containing mixtures are in the same order of magnitude with the respective pure organic components. A monotonic increase in the densities and viscosities of the mixed solvents is observed as the mole fraction of DES in the mixture increases, with the exception of the density of ethaline-propylene carbonate which shows the opposite behavior due to the high viscosity of the pure organic component. The self-diffusivities of all species in the mixtures significantly decrease as the mole fraction of DES approaches unity. Similarly, the self-diffusivities of the dissolved CO2 and the oxalic and formic acids also decrease by at least 1 order of magnitude as the composition of the mixture shifts from the pure organic component to pure DES. The computed ionic conductivities of all mixed solvents show a maximum value for mole fractions of DES in the range from 0.2 to 0.6 and decrease as more DES is added to the mixtures. Since for most mixtures studied here no prior experimental measurements exist, our findings can serve as a first data set based on which further investigation of DES-containing electrolyte solutions can be performed for the electrochemical reduction of CO2 to useful chemicals.

A review on application of deep eutectic solvents as green catalysts and co-solvents in biodiesel production and purification processes

A review on application of deep eutectic solvents as green catalysts and co-solvents in biodiesel production and purification processes

Thermophysical characterization of deep eutectic solvents composed by D-sorbitol, xylitol or D(+)xylose as hydrogen bond donors

Deep eutectic solvents (DES), a class of green solvents of simple preparation, presents high biocompatibility being able to be applied by pharmaceutical and food industry. The aim of this work was to determine density, viscosity, and speed of sound of DES composed by sugar hydrogen bond donors (HBD) (D-sorbitol, xylitol and D(+)xylose) and cholinium chloride as hydrogen bond acceptor (HBA). In addition, the effect of HBA:HBD molar ratio and temperature on thermophysical properties was determined. Results implies that both HBA:HBD molar ratio and temperature influence the thermophysical characteristics of the DES. Higher temperatures decrease the DES density and viscosity and increase the speed of sound. The sorbitol displays the most compact structure presenting higher density, viscosity and speed of sound values when compared to xylitol and xylose-based DES. Results presented in this work may help in the application of sugar-based DES by food industry and in the understanding of these solvents behavior for future separation process studies.

Application of deep eutectic solvents in water treatment processes: A review

Over the past decade, deep eutectic solvents (DESs) have gathered considerable attention in the research for functional and green solvents. The significant focus on the utilization of DESs can be attributed to their economic benefits over ionic liquids (ILs), practical usage through their flexible design, and environmental safety linked to their potential biodegradability and low toxicity, as well as low vapor pressure. Since their development in 2003, DESs have proved to offer tremendous opportunities, opening new perspectives as novel and refined materials. To date, significant advances have been achieved in the synthesis and applications of DESs, with more than ten thousand journal papers documented on this topic across different scientific fields. In particular, the use of DESs in water and wastewater treatment has rapidly emerged as a promising application area for advancing industrial and analytical processes given their beneficial and unique physicochemical properties. This review surveys the state-of-the-art on the application of different classes of DESs in water purification treatment, focusing on membrane separation, and microscale extraction processes. The current problems in the integration of DESs in water treatment processes and technologies are mentioned, and potential research directions to address the challenges are recommended.

A review on recent applications of deep eutectic solvents in microextraction techniques for the analysis of biological matrices

In general, the analysis of biological matrices is challenging and a sample preparation step employing extraction/cleanup techniques is required. Liquid-phase microextraction using deep eutectic solvents has been exploited in numerous applications because these solvents exhibit fascinating physico-chemical properties in addition to simple and straightforward preparation. Varied configurations and strategies have been examined for the determination of different classes of analytes, and these methodologies offer environmentally friendly workflows with low solvent and sample consumption, rapid and simple experimental procedures, and satisfactory analytical performance. In this review, developments related to the use of deep eutectic solvents in microextraction approaches for the analysis of biological matrices are briefly discussed with a focus on studies reported from 2017 to 2021.

Application of Deep Eutectic Solvents in the Synthesis of Substituted 2-Mercaptoquinazolin-4(3H)-Ones: A Comparison of Selected Green Chemistry Methods.

In this study, deep eutectic solvents (DESs) were used as green and eco-friendly media for the synthesis of substituted 2-mercaptoquinazolin-4(3H)-ones from different anthranilic acids and aliphatic or aromatic isothiocyanates. A model reaction on anthranilic acid and phenyl isothiocyanate was performed in 20 choline chloride-based DESs at 80 °C to find the best solvent. Based on the product yield, choline chloride:urea (1:2) DES was found to be the most effective, while DESs acted both as solvents and catalysts. Desired compounds were prepared with moderate to good yields using stirring, microwave-assisted, and ultrasound-assisted synthesis. Significantly, higher yields were obtained with mixing and ultrasonication (16–76%), while microwave-induced synthesis showed lower effectiveness (13–49%). The specific contribution of this research is the use of DESs in combination with the above-mentioned green techniques for the synthesis of a wide range of derivatives. The structures of the synthesized compounds were confirmed by 1H and 13C NMR spectroscopy.

Ultrasound assisted extraction of phenolic compounds from Capparis Ovata var canescens fruit using deep eutectic solvents

The aim of this study is to develop a green procedure that provides high-efficiency extraction of phenolic compounds from Capparis Ovata fruit with Deep Eutectic Solvent (DES) using ultrasound-assisted extraction method. Ten DES combinations were prepared by mixing various proportions of choline chloride (ChCl), Na-acetate and Na-citrate with sugar alcohols, carboxylic acid. These DESs were tested as an effective solvent for recovering phenolic compounds. DES composed of lactic acid combining with ChCl showed the highest efficiency of extraction for phenolic compounds. Optimal extraction conditions were found as follows; 20% water in DES, liquid/solid ratio 20:1 (mL/g), temperature 50℃, and extraction time 30 min. The maximum total phenolic content, total flavonoid content, DPPH inhibition percentage, and ferric reducing power capacity values under optimal conditions were 30.55 ± 0.57 mg GAE/g DW, 13.04 ± 0.4 mg QE/g DW, 98.49 ± 2.51% and 1.79 ± 0.04 (absorbance units), respectively. The concentrations of all phenolic compounds determined by chromatographic method have increased under optimal extraction conditions. Practical applications The application of DES in the extraction of the phenolic compound is an innovative approach for environmentally, friendly, low-costs, and improving extraction efficiency. Caper fruits are known to be rich sources of bioactive compounds. Caper is consumed as food and traditional folk medicines for their health benefits. At previous studies, a green extraction procedure to obtain phenolic compounds from Capparis Ovata var canescens fruit has not been established by using DES. Therefore, this study aimed to improve a green procedure to obtain phenolic compounds with strong antioxidant properties, which could be employed in the food industry. In addition, determination of optimal extraction conditions has been performed to guide large-scale production.