Application Of Deep Eutectic Solvents Research Articles

The application of deep eutectic solvents for protein extraction from bee bread (Perga)

Bee bread is one of the basic nutrients that bees use as a protein source and is formed as a result of the fermentation of bee pollen. In the last few years, this product has become increasingly recognized and consumed among bee products due to its functional properties. However, deep eutectic solvents (DES) have attracted great interest in recent years as promising green alternatives to replace traditional solvents due to their variable viscosity, low vapor pressure, application-specific adjustability, non-flammability and chemical stability. In this study, bee bread was extracted in 12 different DES with different hydrogen bond acceptor (HBA):hydrogen bond donor (HBD) combinations. The DES combination with the highest total protein content was determined to be choline chloride (ChCl)-urea. Then, ultrasonic extraction conditions were optimized for maximum bioactive extraction in extracts prepared with ChCl-urea. The optimum conditions were found as 31.3 %, 25 min, 35 °C for ultrasonic power, extraction time and temperature, respectively. The desirability value (d) of the model was 0.83. The extracts were analyzed for total phenolic content, total protein content, individual polyphenolics, individual amino acids and individual vitamins as well as antimicrobial and antioxidant activity tests. According to the results, total protein, total individual amino acids and total individual phenolics were higher in the extracts obtained with ChCl-urea compared to the extract prepared with conventional solvent (ethanol). In conclusion, all these findings showed that ChCl-urea combination can be an alternative to ethanol depending on the structural characteristics of the target compounds to be extracted from bee bread.

Addressing the Reuse of Deep Eutectic Solvents in Li-ion Battery Recycling: Insights Into Dissolution Mechanism, Metal Recovery, Regeneration and Decomposition.

Deep eutectic solvents (DESs) have garnered attention in Li-ion battery (LIB) recycling due to their declared eco-friendly attributes and adjustable metal dissolution selectivity, offering a promising avenue for recycling processes. However, DESs currently lack competitiveness compared to mineral acids, commonly used in industrial-scale LIB recycling. Current research primarily focuses on optimizing DES formulation and experimental conditions to maximize metal dissolution yields in standalone leaching experiments. While achieving yields comparable to traditional leaching systems is important, extensive DES reuse is vital for overall recycling feasibility. To achieve this, evaluating the metal dissolution mechanism can assist in estimating DES consumption rates and assessing process makeup stream costs. The selection of appropriate metal recovery and DES regeneration strategies is essential to enable subsequent reuse over multiple cycles. Finally, decomposition of DES components should be avoided throughout the designed recycling process, as by-products can impact leaching efficiency and compromise the safety and environmental friendliness of DES. In this review, these aspects are emphasized with the aim of directing research efforts away from simply pursuing the maximization of metal dissolution efficiency, towards a broader view focusing on the application of DES beyond the laboratory scale.

Application of deep eutectic solvents on extraction of flavonoids.

Deep eutectic solvents (DESs), as a new type of eco-friendly solvent, have attracted increasing attention on the extraction and separation of flavonoid compounds from various samples, owing to their excellent properties such as biodegradability and ease of handling with very low toxicity. This article provides a status review of the applications of DESs in the extraction of flavonoids, including the introduction of flavonoid compounds, the properties and superiority of DESs, and extraction methods (ultrasonic-assisted extraction, heating reflux extraction, matrix solid-phase dispersion, and solid-phase extraction). Finally, prospects and challenges in the application of DESs on extraction and separation are extensively elucidated and critically reviewed.

Deep eutectic solvents recovery with bipolar membrane electrodialysis in biorefinery: An economic study

The complex composition and shortage of recycle technology restricted application of deep eutectic solvents (DES). Bipolar membrane electrodialysis has been proven efficient for DES recovery in biorefinery. A comprehensive economic study was essential prior to industrial recovery of DES with bipolar membrane electrodialysis (BMED). An economic study of the BMED-based recovery technique was performed by ascertaining influence of major factors on DES recovery charge with sensitivity analysis. Recovery charge of three representative types of DES was found to be changed within 0.83–1.66 $/Kg (choline chloride-ethylene glycol), 1.60–3.88 $/Kg (lactic acid-ethylene glycol), and 1.21–2.44 $/Kg (choline chloride-urea) as each factor altered in the control. Proportion of annual operating duration and loan duration displayed a negative correlation with the total recovery charge of DES. Multiple of membrane price, factor of membrane facility charge, factor of ancillary facility charge, factor of annual maintaining charge, annual reduction of recovery ratio, annual increase of recovery energy consumption, and annual interest rate of loan showed a positive relationship with the recovery charge. Total DES recovery charge increased within 6.0 %–6.4 % when heterogeneous ion-exchange membranes were employed in BMED facility instead of homogeneous ion-exchange membranes. This study verified the economic virtue of BMED-based DES recovery strategy in biorefinery.

Role of Oxidants in Metal Extraction from Sulfide Minerals in a Deep Eutectic Solvent.

Metallurgical applications of deep eutectic solvents (DESs), known as ionometallurgy, have received significant research attention in recent years. While many studies claim that DESs are generally green and enhance process efficiency, others believe that industrial applications of ionometallurgy are generally not viable. Here, we report on leaching experiments of a sulfide flotation concentrate using ethaline, a chloride-based DES, in the presence of common oxidants. Following a mineral-based approach, we compare results with those obtained from aqueous chloride solutions to assess the influence of the leaching medium. We aim to contribute to a basic understanding of key differences between DESs and aqueous solutions and hope that this will help to make informed decisions about the suitability of DESs for leaching applications. Experiments were performed on a feed concentrate comprising a mixture of sulfide minerals along with substantial concentrations of Au, Ag, and Te. We found similar leaching behaviors for ethaline and aqueous solutions in nonoxidative leaching. However, when oxidizing agents were introduced, ethaline exhibited higher leaching efficiencies. Notably, the oxidation rate of pyrite in ethaline was very low, while chalcopyrite exhibited high oxidation rates. Furthermore, the results highlight significant variations in leaching rates depending on the type of oxidant, with the highest rate observed for I2, followed by CuCl2, and FeCl3. H2O2 and O2 were less effective. The leaching of gold-silver tellurides was possible in ethaline. This could be of particular significance, given that Au-Ag-Te compounds pose challenges in conventional cyanide treatment.

Fractionation of oil palm fronds using ethanol-assisted deep eutectic solvent: Influence of ethanol concentration on enhancing enzymatic saccharification and lignin β-O-4 content

Numerous fractionation methods have been developed in recent years for separating components such as cellulose, hemicellulose, and lignin from lignocellulosic biomass wastes. Deep eutectic solvents (DES) have recently been widely investigated as captivating green solvents for biomass fractionation. However, most acidic-based deep eutectic solvent fractionation produces condensed lignin with low β-O-4 content. Besides, most DESs exhibit high viscosity, which results in poor mass transfer properties. This study aimed to address the challenges above by incorporating ethanol into the deep eutectic solvent at various concentrations (10–50 wt%) to fractionate oil palm fronds at a mild condition, i.e., 80 °C, 1 atm. Cellulose residues fractionated with ethanol-assisted deep eutectic solvent showed a maximum glucose yield of 85.8% when 20 wt% of ethanol was incorporated in the deep eutectic solvent, significantly higher than that achieved by pure DES (44.8%). Lignin extracted with ethanol-assisted deep eutectic solvent is lighter in color and higher in β-O-4 contents (up to 44 β-O-4 per 100 aromatic units) than pure DES-extracted lignin. Overall, this study has demonstrated that incorporating ethanol into deep eutectic solvents could enhance the applicability of deep eutectic solvents in the complete valorization of lignocellulosic biomass. Highly enzymatic digestible cellulose-rich solid and β-O-4-rich lignin attained from the fractionation could serve as sustainable precursors for the production of biofuels.

Deep Eutectic Solvents as Catalysts in the Synthesis of Active Pharmaceutical Ingredients and Precursors

Deep Eutectic Solvents (DESs) have appeared in recent years as an appealing alternative to classical organic solvents, due to their valuable environmental properties. In addition, these compounds, formed by the combination of one hydrogen bond donor with a hydrogen bond acceptor at a defined stoichiometric ratio, present other valuable activities not only as a reaction medium. DESs can also be employed as catalysts through hydrogen-bond interactions in different chemical transformations, thus substituting hazardous reagents and solvents. The search for novel and more environmentally friendly catalysts is an area of interest of pharmaceutical chemists, and therefore, the efforts made in the application of DESs as catalysts in the synthesis of APIs or its precursors are described, focusing mainly on condensations, nucleophilic additions to carbonyl moieties, and multicomponent reactions.

Highly efficient DES-based catalytic systems for carbon dioxide utilization via cycloaddition with epoxide substrates

The accumulation of greenhouse gases (GHG) in the atmosphere, with carbon dioxide being the most significant contributor, is a major environmental problem as it impacts significantly on climate change. The development of new catalysts and chemical reactions that incorporate CO2 are needed to reduce its further emission significantly. Deep eutectic solvents (DES) have garnered increasing attention as environmentally friendly catalysts in the cycloaddition of carbon dioxide (CO2) with epoxide substrates to produce cyclic carbonates. Their appeal stems from their facile synthesis, cost-effectiveness, low vapour pressure, and thermal stability. In this study, we present a convenient solvent-free synthesis method for nine deep eutectic solvents (DES), utilizing varying compositions of quaternary amine salts (N,N,N-triethyldodecan-1-aminium hydroxide, [TEA-12][OH]) and quinaldic acid [Q-COOH]. These deep eutectic solvents were thoroughly characterized using several techniques, including FTIR, NMR, DSC, and TGA. Moreover, their efficacy for the solvent-free fixation of CO2 to cyclic carbonates were evaluated. Among the tested compositions, [TEA-12]:[Q-COOH] (0.9:0.1) exhibited the lowest melting point (100.17 °C) and highest catalytic activity, showcasing an optimized Turn-Over Frequency (TOF) of 1466 h−1. This remarkable result represents a significant advancement in the application of DES for CO2 fixation, exceeding the previous highest catalytic activity observed with TBAB:Citric acid (2.5:1) by more than tenfold.

Emerging applications of deep eutectic solvents in the preparation and functionalization of biomass-derived carbonaceous materials: challenges and prospects

Deep eutectic solvents can be used as the pretreatment solvents, carbon precursors, soft templates, carbonization media, and post-modification agents for the preparation and functionalization of biomass-derived carbonaceous materials.

Solvent‐Mediated Synthesis of Functional Powder Materials from Deep Eutectic Solvents for Energy Storage and Conversion: A Review

AbstractDeveloping advanced electrochemical energy storage and conversion (ESC) technologies based on renewable clean energy can alleviate severe global environmental pollution and energy crisis. The efficient preparation of functional electrode materials via a simple, green, and safe synthesis process is the key to the commercial feasibility of these ESC systems. Deep eutectic solvents (DESs) with easy‐tunable solvent properties and recyclable features have emerged as novel solvent systems for designing and synthesizing various functional powder materials for ESC devices. In this paper, the application of DESs in the synthesis of energy‐related functional powder materials is systematically reviewed. After briefly introducing the classification and synthesis of DESs, their critical roles in synthesizing powder materials are discussed. Then, the recent advances of DES‐derived powder materials in ESC, including batteries, fuel cells, supercapacitors, and water splitting, are described in detail from the perspective of preparation‐structure‐activity. Finally, some challenges and development directions of the DESs‐mediated synthesis of powder materials with high electrochemical performance for ESC applications are outlined.

Application of Deep Eutectic Solvents in Formation of Carbon‐Carbon and Carbon‐Heteroatom Bond by Cross‐Coupling Reactions

AbstractDeep eutectic solvents (DESs), known as the emerging organic reaction medium in the 21st century, have many advantages such as cheap, readily available, non‐pollution, and biodegradable. Its good properties make it an alternative to volatile organic solvents. The insights in to carbon‐carbon and carbon‐heteroatom bond formations and their applications since 2017 are encapsulated, which not only highlighting the significant achievements pertaining to the important role of DESs as solvents but also including popular named organic reactions for cross‐coupling reactions relating to the nature of DESs and the core optimum conditions. The review also encompasses a brief overview of the current situation and future development of DESs.

Deep eutectic solvents as a green alternative for trace element analysis in food and beverage samples: Recent advances and challenges

Metals and metalloids have different effects on human health even at trace levels. Some of them are essential for living organisms while others can be toxic. Therefore, the determination of trace elements in food and beverage is highly important to understand their impact in human health. A new generation of solvents named deep eutectic solvents (DES) has emerged as a green alternative for trace element analysis, owing to their low toxicity, biodegradability, and high extraction capacity. In recent years, the application of DES in extraction techniques for trace element analysis in food and beverage samples has increased significantly. This review summarizes recent advances and challenges on the application of DES to develop microextraction techniques useful for the analysis of samples with complex matrices. The importance of the use of biodegradable substances instead of classic organic solvents, which are toxic, volatile, and flammable in methods for elemental analysis with a positive environmental impact is also highlighted. Finally, conclusions and future challenges arising from the use of DES in microextraction techniques are discussed.

Facile fabrication of NaOH nanorods on pencil graphite electrode for simultaneous electrochemical detection of natural antioxidants by deep eutectic solvent

We report the application of deep eutectic solvents (DES) based on ethylene glycol and urea as low-cost, green, and suitable electrolytes for electrochemical studies. The main aim of this study was to explore the capabilities of DES as an enhancer of electrochemical detection for the natural antioxidants of ascorbic acid (AA) and gallic acid (GA). A simple fabrication of a disposable and effective electrochemical sensing platform for the simultaneous determination of AA and GA based on the one-step electrochemical deposition of NaOH nanorods on pencil graphite electrode (PGE) was performed. The electrochemical behavior showed that the two antioxidants, AA and GA, could be electro-oxidized and discriminated simultaneously on the surface of the NaOH/PGE. The oxidation potentials of AA and GA shifted slightly towards negative, and the peak current values increased 2.0-fold in DES than in BR buffer medium. Due to the strong synergistic effect between the nanostructures of NaOH (large effective surface area) and DES (high electrical conductivity), the proposed electrode led to the enhancement analytical performances towards AA and GA. Cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy were used to examine the modified electrode's morphological and electrochemical characterization and performance parameters. The developed sensor exhibited good performance towards the determination of AA and GA with a low detection limit (1.4 µM for AA and 0.6 µM for GA), wide linear concentration ranges (2–200 µM for AA and 1–30 µM for GA), and good reproducibility (1.4 % for AA and 0.4 % for GA). The effects of possible interferences were investigated for their effect on the determination of AA and GA. With good selectivity and sensitivity, the sensor's reliability for the simultaneous detection of AA and GA in mineral water (flavored with green tea and vitamin C) was successfully tested. The mean analytical recovery was 100.4 ± 2.5 and 96.2 ± 0.6 for AA and GA, respectively. The results obtained with the presented sensor were confirmed by the HPLC method. This is a promising approach for the determination of the detection of AA and GA in different water samples.

Developing amino acid-citric acid-based deep eutectic solvent for food applications: Preparation, characterization, antibacterial activity, biosafety, and formation mechanism exploration

The deep eutectic solvent (DES) is a novel environmentally-friendly solvent that shows promising potential for applications in the field of functional food. However, the current development of choline-based DESs faces limitations due to their toxicity levels, which restrict their application in the food industry. Therefore, in this study, amino acid (AA)-citric acid (CA) DESs suitable for functional food applications were developed using natural food additives as raw materials. The purity and thermodynamic properties of the AA-CA DESs were characterized by simultaneous thermogravimetry/differential scanning calorimetry (TG-DSC) and DSC analysis. The molecular interactions within the AA-CA DESs were investigated using FT-IR, NMR, and molecular dynamics (MD) simulations. The rheometer was used to study the viscosity of AA-CA DESs. The density of the AA-CA DESs was tested using a pycnometer and mutually verified with MD simulations. The antibacterial activity and biological safety of DESs were investigated by bacteriostatic and cell experiments. FT-IR, NMR, and MD simulations studies indicated that AA-CA DESs primarily form through hydrogen bonding interactions. Antibacterial experiments demonstrated that AA-CA DESs exhibited significantly enhanced antibacterial activity against P. aeruginosa and E. coli compared to pure substrates Gly, Ala, and Arg, respectively, indicating improved antibacterial properties. The cell experiments showed that AA-CA DESs possess good biological safety. In conclusion, this study successfully developed a class of AA-CA DESs and found that AA-CA DESs have good antibacterial activity and biosafety. This finding provides theoretical guidance for the sustainable development and application of DESs in the field of functional foods.

Ternary deep eutectic solvent enhanced the diffusion control of amine monomer for highly permeable and anti-fouling polyamide nanofiltration membranes

Thin-film composite nanofiltration (TFC NF) membranes have been widely used in water treatment, while the common active polyamide (PA) separation layer suffers the problems of excessive mass transfer resistance and fouling. In this work, a novel ternary deep eutectic solvent (DES) of citric acid/choline chloride/glycol as an additive in the aqueous phase was focused on regulating the formation of PA layer. The ternary DES can interact with piperazine (PIP) via hydrogen bonding and electrostatic interaction, synergistically enhancing the diffusion control of PIP with viscosity modulation during interfacial polymerization. Notably, a thinner and rougher separation layer with a cellular-like structure was obtained by optimizing the ratio of citric acid in ternary DES. Accordingly, the optimized TFC10%-3 membrane maintained an excellent Na2SO4 rejection (98.8 %) and a 104.7 % increase in pure water permeance (39.5 L·m−2·h−1·bar−1) compared to the original membrane, outperforming commercial membranes and the most NF membranes reported in the literature. Besides, the introduction of citric acid in PA layer increased the surface hydrophilicity and electronegativity of TFC10%-3 membrane, resulting in a higher flux recovery rate (FRR = 93.2 %) of TFC10%-3 membrane than that of TFC10%-0 membrane (FRR = 83.9 %). This study provides a feasible design strategy for the preparation of highly permeable and anti-fouling TFC NF membranes and enrichs the application of ternary DES in water treatment.

Elucidating the Structure, Dynamics, and Interaction of a Choline Chloride and Citric Acid Based Eutectic System by Spectroscopic and Molecular Modeling Investigations.

Eutectic solvent systems are versatile solvents that have found widespread use in numerous applications. Traditional solvents are homogeneous, having only one component, and their chemistry is relatively simple, with some exceptions. On the other hand, deep eutectic solvents (DESs) comprise binary components, generally a donor and an acceptor in hydrogen bonding with varying ratios. The interaction chemistry among the donor and acceptor involved in hydrogen bonding in DESs is complicated. Although numerous research is focused on the synthesis and application of DESs, few studies are reported to elucidate the complex structure and dynamic and interaction behavior of DESs. In this study, we employed calorimetry, vibrational spectroscopy techniques including FTIR and Raman, and nuclear magnetic resonance to derive insight into the structural feature and noncovalent contact of choline chloride (ChCl) and citric acid (CA) while they formed DESs. The 1:1 ChCl/CA eutectic system showed phase transitions and melting peaks with the most pronounced peak at 156.22 °C, suggesting the DESs melting at a lower temperature than the melting temperatures of ChCl and CA. In addition to IR and Raman findings, 1H NMR investigations demonstrate hydrogen bonding intermolecular interactions between ChCl and CA, supporting the formation of 1:1 ChCl/CA DESs based on the deshielded chemical shifts of the proton for Ch. The interaction of the chloride anion with the methyl protons (H4) and methylene protons (H3) of ChCl as well as the strong hydrogen bonding interactions between the hydroxyl hydrogen (H1) of ChCl with one of CA's carbonyl oxygens both supported the formation of conformer E. In addition, molecular dynamics followed by the density functional theory (DFT) was employed to visualize the structure and interaction of DESs using the ωB97XD theory and 6-311++G (d,p) basis set. Both experimental and theoretical IR, Raman, and structural analyses provided evidence of the formation of DESs by possessing hydrogen bonds. These multifaceted experimental and computational investigations provide details of structural and intermolecular interactions of ChCl/CA DESs.

Synthesis of porous organic framework materials based on deep eutectic solvents and their application in solid-phase extraction

This paper reviews the application of deep eutectic solvents (DESs) in the synthesis of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as well as their prospects in the field of solid-phase extraction (SPE). Porous organic frameworks (POFs) have unique properties such as a large specific surface area, high porosity, and easy modification. Thus, these materials are widely applied in the fields of catalysis, adsorption, drug delivery, gas storage, and separation. POFs include MOFs, COFs, conjugated microporous polymers (CMPs), porous aromatic frameworks (PAFs), and covalent triazine frameworks (CTFs). MOFs are constructed from metal ions/clusters and organic ligands through coordination bonds and can be extended in two or three dimensions by repeated coordination with potential voids. COFs are formed from two monomers containing light elements (such as carbon, hydrogen, oxygen, nitrogen, boron, and other elements) via coordination bonds and have large two- or three-dimensional structures. However, conventional POF synthesis methods generally suffer from disadvantages such as long synthesis times, high temperature and pressure requirements, and the use of toxic and hazardous reaction solvents. DES consists of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) bound by hydrogen-bonding interactions. It is a promising green solvent for material synthesis owing to its low vapor pressure, high stability, and ease of preparation. DES can be used to prepare MOFs and COFs and, in specific cases, acts as a structure-directing agent, which has an important impact on the structure and properties of the resulting frameworks. Using appropriate DES formulations, researchers can modulate the crystal structures, pore sizes, and surface properties of MOFs and COFs, resulting in materials with excellent characteristics. SPE is an analytical technique in which a sample solution is added to an SPE column; the sample solution is forced through the stationary phase, and the target compounds are collected for analysis by elution with an organic solvent. Therefore, suitable stationary-phase materials are critical for SPE. Owing to their large specific surface areas and abundant active sites, MOFs and COFs exhibit outstanding adsorption capacity and selectivity in SPE and can effectively enrich target analytes from complex samples. DES-based MOFs and COFs have shown potential use in a wide range of applications, such as in environmental analysis, food testing, and biological sample analysis. Although DES-based MOFs and COFs for SPE are still in the early stages of development, their properties such as efficient enrichment and high selectivity offer good prospects for practical applications. Future research should continue to explore DES-based synthesis methods in depth to prepare other MOFs and COFs with the desired properties and investigate their potential applications in various fields. These efforts are expected to apply these novel materials in commercialized solid-phase extraction methods, bringing new development opportunities in the field of analytical chemistry.

Green Extraction of Polyphenols via Deep Eutectic Solvents and Assisted Technologies from Agri-Food By-Products.

Polyphenols are the largest group of phytochemicals with important biological properties. Their presence in conveniently available low-cost sources, such as agri-food by-products, has gained considerable attention in their recovery and further exploitation. Retrieving polyphenols in a green and sustainable way is crucial. Recently, deep eutectic solvents (DESs) have been identified as a safe and environmentally benign medium capable of extracting polyphenols efficiently. This review encompasses the current knowledge and applications of DESs and assisted technologies to extract polyphenols from agri-food by-products. Particular attention has been paid to fundamental mechanisms and potential applications in the food, cosmetic, and pharmaceutical industries. In this way, DESs and DESs-assisted with advanced techniques offer promising opportunities to recover polyphenols from agri-food by-products efficiently, contributing to a circular and sustainable economy.

Determination of selenium in cereal and biofortified samples by ICP-OES using an alcohol-based deep eutectic solvent in digestion procedure

The application of deep eutectic solvents (DESs) as green solvents in analytical chemistry has attracted increasing attention. The present study presents a simple, eco-friendly, and cost-effective approach for the extraction of selenium (Se) in food samples. The extraction method utilised alcohol-based DES and inductively coupled plasma optical emission spectrometry (ICP-OES) to determine total Se. Factors affecting the extraction procedure were optimised using the design of experiments. Using the optimal conditions, the limits of detection (LOD) and quantification (LOQ) and linearity of the developed method were 0.0011 µg Se/g, 0.0037 µg Se/g and 0.004–0.20 µg Se/g, respectively. The precision expressed as relative standard deviations (RSDs) was less than 10 %. The accuracy of the method was investigated using certified reference materials (IRMM 804 Rice Flour and NIST SRM 1567b wheat flour), and the results were in close agreement with the certified values (0.038 µg/g and 1.14 µg/g) with percentage recoveries ranging from 89.5 to 106 %. The interday ( %RSD) and Intraday ( %RSD) were 2.8–5.4 % and 4.3–5.9 %, respectively. The greenness of the method was assessed using NEMI, AES, and AGREE metrics tools. When comparing all these tools, they all qualified the proposed method as green.

Application of deep eutectic solvents (DESs) as a green lixiviant for extraction of rare earth elements from caustic-treated monazite concentrate

Rare earth elements (REEs) with unique metallurgical properties are listed as some of the most strategically important elements in today’s world. Monazite is one of the main natural minerals for REEs which is being processed using inefficient conventional hydrometallurgical approaches with extreme environmental footprints. In this paper, an attempt was made to apply deep eutectic solvents (DESs) as a green replacement for conventional solvents such as sulfuric acid and hydrochloric acid in the process of monazite leaching. After the characterization of the monazite concentrate, eleven different DESs were synthesized and employed for the leaching experiments. Results showed that each of the synthesized DES was unable to extract REEs from the phosphate phase. By sodium hydroxide roasting at 500 °C for 2 h followed by water leaching, rare earth hydroxides were formed from the monazite concentrate, and the new phase was characterized. Each of the eleven synthesized DES was tested on the roasted sample and it was revealed that 2ChCl:1PTSA, 2ChCl:1PTSA:1EG, and 1PEG-400:1PTSA have respectively the highest extraction efficiency. The DES comprised of 2ChCl:1PTSA exhibited significant capability for extraction of REEs from the roasted sample with more than 90 % recovery. Further experiments were carried out on the leaching process with 2ChCl:1PTSA for studying the effect of temperature, solid percentage, and time on the final recovery. At the optimum condition, the recoveries of the main REEs including Ce, La, and Nd reached 99.8 %, 99.9 %, and 94 %, respectively. These findings have implications for the development of more efficient and eco-friendly methods for REE recovery from monazite.