Acid-based Deep Eutectic Solvents Research Articles

One-step selective separation and efficient recovery of valuable metals from spent lithium batteries by phosphoric acid-based deep eutectic solvent

With more and more lithium-ion batteries (LIBs) being put into production and application, precious metals such as lithium and cobalt are scarce, so it is imminent to recover various strategic metal resources from spent LIBs. Meanwhile, the complex and difficult problem of separating and recovering metals from leaching solutions has been an urgent question that needs to be resolved. In this work, a phosphoric acid-based deep eutectic solvent (DES) was developed for extracting metals from spent LIBs and one-step selectively separating and efficiently recovering transition metal. The prepared DES shows excellent extraction performance for Li (100%) and Co (92.8%) at 100 °C. In addition, the extraction system can effectively separate and precipitate Co through its own components, avoiding the introduction of new precipitants and the destruction of the original composition structure of DES. This also contributes to the good cycle stability of the extraction system with excellent extraction performance for Li (94.3%) and Co (80.8%) after 5 cycles. This work proposes a green method for one-step selectively separating and recovering valuable metals from spent LIBs.

The gentisic acid-based deep eutectic solvent mediated green synthesis of acridines

A novel gentisic acid-based deep eutectic solvent (ETPPBr/GA-DES) was prepared by mixing of ethyltriphenylphosphonium bromide (ETPPBr) and gentisic acid (GA = 2,5-dihydroxy-benzoic acid), and its structure fully investigated by using the FT-IR, TGA/DTA, densitometer and 1HNMR techniques. Different mole ration of ETPPBr to GA were examined and the eutectic point phase diagram showed that the best ratio for the synthesis of a novel gentisic acid-based DES is the one-to-one mole ratio of the two starting materials (ETPPBr and GA).Then, ETPPBr/GA-DES was used as a novel and capable catalyst for the green synthesis of diverse N-substituted decahydroacridine-1,8-diones a(1−12) from the three-component condensation reaction of aromatic aldehyde, aromatic amine and dimedone in solvent-free conditions at 80 °C.

Development and validation of a deep eutectic solvent-assisted liquid-liquid extraction method for simultaneous quantification of six steroid hormones in serum by liquid chromatography-tandem mass spectrometry

Steroid hormones have been reported to be associated with endocrine system diseases. This paper proposes a novel procedure of deep eutectic solvent (DES)-assisted liquid–liquid extraction (LLE) to extract six steroid hormones (including cortisone, cortisol, androstenedione, testosterone, 17-hydroxyprogesterone, and progesterone) from serum coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of five types of L-proline, choline chloride, and citric acid-based DESs were tailored; the DES from L-proline and ethylene glycol at a molar ratio of 1:4 with 20 % acetonitrile was selected as the best-fit assisted solvent for the six steroid hormones compared with other DESs. The parameters for extraction by selected DES were optimized using Box-Behnken design (BBD), and the optimal extraction conditions are 200 µL of acetonitrile, 100 µL of the sample, and 80 µL of DES. Under optimum conditions, the method has good linear calibration ranges (between 0.07 ng mL−1 and 600 ng mL−1), correlation coefficients of determination (r2>0.99), and low limits of quantification (between 0.02 and 0.60 ng mL−1). The extraction recoveries were in the range of 81.84–114.43 %, and the intra-day and inter-day relative standard deviations (RSDs) were less than 10 %.In general, the DES-LC-MS/MS method is a simple and environmentally-friendly method, which can be complementary to the presently available methods for determining steroid hormones in serum.

Solvometallurgical recycling of spent LiNixCoyMnzO2 (NCM) cathode material using ternary choline chloride-ethylene glycol-p-toluenesulfonic acid deep eutectic solvent

In recent years, recycling lithium-ion batteries (LIBs) has become imperative considering their growing demand will soon lead to massive disposal of spent LIBs which causes critical environmental problems. In this study, solvometallurgy using deep eutectic solvents (DESs) is used to efficiently recover valuable metals from spent LIBs. The potential of different types of DES (binary and ternary) to leach LIB samples is evaluated. Initial leaching tests demonstrate that p-toluenesulfonic acid (PTSA) -based DES results in high metal extraction at 100 °C with 10 g/L pulp density and 72 h residence time. Cyclic voltammetry indicates a high current density of PTSA, a strong leaching agent in the DES structure. A ternary DES containing choline chloride, ethylene glycol, and p-toluenesulfonic acid (ChCl-EG-PTSA) show better performance as a leachant than other DESs. The formation of hydrogen bonds between p-toluenesulfonic acid-based DES components is examined by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. This study provides a new ternary DES for solvometallurgical recycling of LIBs while considering principles for sustainable development.

Comparative of malonic acid aqueous solution and malonic acid-based deep eutectic solvent for LiCoO2 cathode materials recovery: Leaching efficiency and mechanism

Deep eutectic solvents (DESs) and aqueous organic acids are two leaching systems that have achieved remarkable results in hydrometallurgical recovery of spent lithium-ion batteries (LIBs). However, previous studies have only evaluated a single leaching system at a time and thereby failed to compare the differences between DES and organic acids systems in detail. In this study, our purpose was to clarify the differences between the efficiencies of two leaching systems—a malonic acid (MA) aqueous solution and a DES of choline chloride: malonic acid (ChCl:MA) via a systematic investigation of the conditions and mechanisms associated with the leaching of LiCoO2 cathode materials using these two systems. The effects exerted by various process parameters, such as reaction time, temperature, and liquid-to-solid ratio, on the leaching efficiency of these two systems were investigated. The results showed that the Co and Li leaching efficiencies of the DES were higher than those of the MA aqueous solution under identical experimental conditions. The kinetic differences between the two systems were reflected in the fact that the MA aqueous solution was regulated by diffusion, whereas the DES leaching was regulated by chemical reactions. Spectroscopic analysis and density functional theory calculations indicated that MA acts as both a ligand and a reducing agent in aqueous solutions, whereas MA in the DES only acts as a reducing agent. In addition, Co was present in the MA aqueous and DES leaching solutions as octahedral (Co(H2O)2(C3H2O4)2) and tetrahedral ([CoCl4]2-), respectively.

The Novel Catalyst (Hypogallic Acid-Based Deep Eutectic Solvent) for Preparation of the New Compounds (Pyrano[2,3-d]Pyrimidines)

A novel Deep Eutectic Solvent (MTPPBr/HGA-DES) was prepared by a mixture of methyl triphenylphosphonium bromide (MTPPBr) and hypogallic acid (HGA: 2,3-dihydroxybenzoic acid). The eutectic point phase diagram showed that the one mole of MTPPBr to two moles of HGA is the best mole ratio for the synthesis of a novel DES. Then, MTPPBr/HGA-DES was characterized by the FT-IR, TGA/DTA, densitometer, eutectic points, and 1H NMR techniques, and used as a novel catalyst for the green synthesis of new pyrano[2,3-d]pyrimidines 2(a-j) via a one-pot four-component condensation reaction of 4-hydroxycoumarin, barbituric acid, morpholine and benzaldehydes at 80 °C in solvent-free conditions.

Sustainable extraction of polyphenols from vine shoots using deep eutectic solvents: Influence of the solvent, Vitis sp., and extraction technique

Vine shoots are the main by-products of grapevine pruning with no added value. In the present study, deep eutectic solvents (DESs) were used as alternatives to traditional chemical solvents, for the extraction of phytochemicals from grapevine shoots. Three levulinic acid-based DESs were tested for the first time, and their performance was compared to methanol (a standard chemical solvent) regarding the extraction of phenolic compounds from thirteen Vitis sp. shoots. Two extraction methods have been applied: ultrasound-assisted extraction and solid-liquid extraction. A total of eleven polyphenols which belongs to four families (proanthocyanins, stilbenes, hydroxycinnamic acids, and flavonols) have been identified and quantified in the extracts.The statistical analysis shows that the levulinic acid-based DES systems are novel and important alternatives to chemical solvents due to favourable eco-friendly properties and remarkable extraction performance of polyphenols. On the other hand, the ultrasound-assisted extraction technique has significantly increased the extraction rate in comparison to the solid-liquid extraction method with p-values lower than 0.05 for most compounds. The genetic factor has been shown to play an important role in the content of extracted polyphenols, being V. riparia pubescente the one that presented the highest concentrations of extracted polyphenols. Finally, the polyphenol-enriched extracts have proven important properties such as antioxidant activity and significant delay in bacteria growth against both gram-positive and gram-negative bacteria. It is important to note that, to the best of our knowledge, this is the first time that deep eutectic solvents have been used for the extraction of bioactive compounds from vine shoot residues.

Glycolic acid-based deep eutectic solvents boosting co-production of xylo-oligomers and fermentable sugars from corncob and the related kinetic mechanism

BackgroundXylo-oligomers are a kind of high value-added products in biomass fractionation. Although there are several chemical methods to obtain xylo-oligomers from biomass, the reports about the deep eutectic solvents (DESs)-mediated co-production of xylo-oligomers and fermentable sugars and the related kinetic mechanism are limited.ResultsIn this work, glycolic acid-based DESs were used to obtain xylo-oligomers from corncob. The highest xylo-oligomers yield of 65.9% was achieved at 120 °C for 20 min, of which the functional xylo-oligosaccharides (XOSs, DP 2–5) accounted for up to 31.8%. Meanwhile, the enzymatic digestion of cellulose and xylan in residues reached 81.0% and 95.5%, respectively. Moreover, the addition of metal inorganic salts significantly accelerated the hydrolysis of xylan and even the degradation of xylo-oligomers in DES, thus resulting in higher selectivity of xylan removal. AlCl3 showed the strongest synergistic effect with DES on accelerating the processes, while FeCl2 is best one for xylo-oligomers accumulation, affording the highest xylo-oligomers yield of 66.1% for only 10 min. Furthermore, the kinetic study indicates that the ‘potential hydrolysis degree’ model could well describe the xylan hydrolysis processes and glycolic acid/lactic acid (3:1) is a promising solvent for xylo-oligomers production, in particular, it worked well with FeCl2 for the excellent accumulation of xylo-oligomers.ConclusionsGlycolic acid-based deep eutectic solvents can be successfully applied in corncob fractionation with excellent xylo-oligomers and fermentable sugars yields on mild conditions, and the large amount of xylo-oligosaccharides accumulation could be achieved by specific process controlling. The strategies established here can be useful for developing high-valued products from biomass.

Green, one-pot biomass hierarchical utilization strategy for lignin-containing cellulose nanofibrils and fractionated lignin preparation

The recalcitrant nature of plant cells makes biomass hierarchical utilization challenging. Here we report a green, one-pot strategy to achieve fractionation of sugarcane pith cellulose and lignin. Lignin-containing cellulose nanofibrils (LCNFs) and fractionated lignin (by tailored choline chloride and oxalic acid-based deep eutectic solvents (DESs) and ultrasonic nanofibrillation pretreatments) were studied. The obtained LCNFs had a well-independent structure and uniform size distribution (5.05–6.88 nm in diameter). Lignin fractionated by diol acid DES (DADES) exhibited a relatively homogeneous molecular weight (Mw, 2013–2827 g/mol), reduced lignin heterogeneity, and condensation under acidic conditions. Besides, multi-functional LCNF papers were prepared by vacuum filtration of their suspensions and had excellent bio-disintegration capability, water resistance, UV-shielding performance, and thermal stability. This study demonstrated that DADES enables hierarchical biomass utilization and successful production of high-value-added building blocks, such as LCNF and fractionated lignin.

Efficient extraction of S-heterocyclic aromatics from fuel oil with oxalic acid-based deep eutectic solvent

The presence of thiophenes in fuel oil not only affects the quality of oil products, but also causes serious environmental problems. The efficient extraction of S-heterocyclic aromatics from fuel oil by π-electron donor-based (i.e., oxalic acid) deep eutectic solvents (DESs) is proposed for the first time. The distribution coefficient and separation factor of n-heptane + 2-methylthiophene/3-methylthiophene/thiophene in 100 DESs were predicted by COSMO-RS model, and the optimal DESs (i.e., Tetraethylammonium chloride-oxalic acid / Tetraethylammonium bromide-oxalic acid) was selected as the potential extractants. The selectivity and extraction capacity of the two DESs were measured and compared by liquid–liquid equilibrium experiments. The thermodynamic consistency of the experimental data was tested by Othmer-Tobias and Hand equations, which show that R2 is>0.95, and the experimental results have high reliability. The interaction mechanism between the extractant and the target systems was analyzed by molecular dynamics simulation and quantum chemical calculation. The results of the mean square displacement and fraction free volume show that thiophene has higher displacement and diffusion in DES2 (i.e., tetraethylammonium bromide and oxalic acid) compared to 2-methylthiophene and 3-methylthiophene molecules. Moreover, the interaction analysis show that electrostatic energy is the main effect between molecules. Finally, the weak interaction between different molecular pairs was identified by the molecular surface electrostatic potential and the independent gradient model. This work provides insight into the design and screening of novel DESs for the extraction and separation of S-heterocyclic aromatics.

Structure investigation of light-colored lignin extracted by Lewis acid-based deep eutectic solvent from softwood

Lignin is the most abundant natural phenolic polymer. However, the severe condensations of industrial lignin resulted in an undesirable apparent morphology and darker color, which hindered its application in the field of daily chemicals. Therefore, a ternary deep eutectic solvent is used to obtain lignin with light-color and low condensations from softwood. The results showed that the brightness value of lignin extracted from aluminum chloride-1,4-butanediol-choline chloride at 100 °C and 1.0 h was 77.9, and the lignin yield was 32.2 ± 0.6%. It is important that 95.8% of β-O-4 linkages (β-O-4 and β-O-4′) was retained. Lignin is used to prepare sunscreens and is added to physical sunscreens at 5%, with SPF up to 26.95 ± 4.20. Meanwhile, enzyme hydrolysis experiments and reaction liquid composition tests were also conducted. In conclusion, a systematic understanding of this efficient process could facilitate high-value utilization of lignocellulosic biomass in industrial processes.

Amino Acid- and Dipeptide Amphiphile-Based Supramolecular Eutectogels: Soft Materials for Drug Entrapment–Release and Wastewater Treatment

Supramolecular gels prepared in solvents of extreme polarities have received widespread importance across scientific disciplines. In this regard, soft materials based on deep eutectic solvents (DESs) have been receiving notable attention owing to their low toxicity, low volatility, and ability to solubilize hydrophobic drugs and natural products. A DES is a mixture of two or more compounds having a melting point lower than that of the individual components. Reports on supramolecular eutectogels derived from small molecules are very few and serendipitous. Therefore, designing a low-molecular-weight eutectogelator (LMWEG) remains challenging and demands comprehensive structure–property correlation. To this end, we have developed amino acid- and dipeptide amphiphile-based LMWEGs that immobilized choline chloride/phenylacetic acid-based DES with a minimum gelation concentration (MGC) of 0.5–10.0%, w/v. Variation of amino acids, protecting groups at the N-terminal, and hydrophobic chain length of the gelator delineated the crucial influence of the hydropathy index of amino acids and thereby the hydrophilic–lipophilic balance in eutectogelation. Replacement of the aromatic moiety in the gelator and/or in the DES with an aliphatic one ascertained the optimal necessity of aromaticity for efficient eutectogelation. Eutectogels were thermoreversible and showed considerable thermal stability (Tgel ∼ 50–70 °C). Spectroscopic and microscopic studies confirmed the fiber-like morphology of the eutectogels and the participation of hydrogen bonding in eutectogelation. Newly derived eutectogels exhibited considerably good mechanical strength (γc ∼ 7.5–16.5%) and interesting injectable as well as thixotropic properties. The ability to adsorb cationic and anionic dyes by the eutectogels ensured their potential in wastewater treatment. Importantly, these supramolecular eutectogels can be used in drug delivery owing to their ability to entrap the hydrophobic drug curcumin and subsequently its pH-dependent sustained release.

Theoretical study of lactic acid-based deep eutectic solvents dissociation of hemicellulose with different hydrogen bonding acceptors

This paper explored the mechanism of dissociation of hemicellulose using lactic acid (LA)-based deep eutectic solvents (DESs) synthesized with different hydrogen bond acceptors (HBAs) via simulations. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations revealed that DESs synthesized with guanidine hydrochloride (GuHCl) as hydrogen bond acceptor (HBA) demonstrated better hemicellulose solubilization compared to the conventional DESs synthesized using choline chloride (ChCl) as HBA. The best interaction with hemicellulose was achieved at GuHCl:LA = 1:1. The results showed that CL− played a dominant role in the dissolution of hemicellulose by DESs. Unlike ChCl, the guanidine group in GuHCl had the delocalized π bond, which made CL− have stronger coordination ability and promoted dissolution of hemicellulose by DESs. Moreover, multivariable analysis was employed to establish the correlation between the effects of different DESs on hemicellulose and the molecular simulation results. Additionally, the influence of different HBAs functional groups and carbon chain length on the solubilization of hemicellulose by DESs were analyzed.

Comparison of extraction abilities of deep eutectic solvents and aqueous acid solutions for extraction of rare earths and transition metals

In recent years, deep eutectic solvents have attracted increasing interest as effective extractants for the separation of both organic substances and metals from various objects. Acid-based deep eutectic solvents are most often used as extractants for the extraction of metals. In this work, for the first time, the extraction efficiency of transition metals and rare earth elements (Y, Zr, Nb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf and Ta) from mining tailings and Na, K, Ca, Mg, Cu, Fe, Mn, Pb, Ba, Ni and Sr from biodiesel samples using acidic deep eutectic solvents and saturated aqueous solutions of the same acids (malonic, malic, tartaric and citric) is compared. For this, deep eutectic solvents based on acids and their aqueous saturated solutions were prepared and studied. The prepared mixtures were analyzed by IR spectroscopy to confirm the formation of eutectic solvents. Properties such as the density and viscosity of the resulting mixtures were also investigated, as this can be of key importance for the efficiency of metal extraction. The extraction of rare earth metals from mining tailings took a long time (up to several days), while the extraction of metals from fuel took no more than 30 min. Atomic emission spectral methods were used as an analysis method. It is shown that the extraction efficiency with aqueous solutions is better than that with eutectic solvents, which casts doubt on the need for deep eutectic solvents use in this area.

Recovery of bismuth and other metals from blast furnace dust by leaching with oxalic acid-based deep eutectic solvent and precipitation

Eutectic solvents, with the advantages of easy synthesis, high chloride content, non-aqueous environment, and low costs are the most promising alternatives to ionic liquids for leaching and recovery of metals from waste resources. The leaching of bismuth has been mainly conducted using chlorinated salts and strong acids in previous studies. The use of conventional ionic liquids can be costly. In addition, there has only been limited research into developing strategies for the recovery of bismuth from blast furnace (BF) dust using a deep eutectic solvent (DES) made of choline chloride and oxalic acid. In this work, an oxalic acid-based deep eutectic solvent was used for selective recovery of bismuth from blast furnace dust. A leaching efficiency of 94.9% Bi was achieved at the most suitable conditions (stirring speed: 300 rpm, liquid-solid ratio: 5 mL/g, temperature: 70°C, time: 20 h). The zinc and iron which are impurities in the leach solution were removed by hydrolysis and photoinduced reduction process, and the by-products of ZnC2O4·2H2O and FeC2O4·2H2O had purities of 86.6% and 96.8%, respectively. Another hydrolysis was employed to recover Bi(III) from the leach solution and the product of BiOCl was obtained with a total Bi recovery efficiency of 89.1%. The proposed process in this work is resource-saving and friendly to the environment.

Effect of Arginine-Based Deep Eutectic Solvents on Supported Porous Sorbent for CO2 Capture Analysis

Carbon dioxide (CO2) as one of the heat-trapping gases, has caused global warming. Being a greener and more economical material, amino acid-based deep eutectic solvents (AADES) have attracted interest in CO2 capture applications. In this paper, the effect of L-arginine (Arg) in binary AADES of arginine-ethylene glycol (Arg-EG) and ternary AADES of choline chloride-ethylene glycol-arginine (ChCl-EG-Arg) on adsorption of CO2 was studied. The solubility, basicity, and physicochemical characteristics were compared with the binary DES (ChCl-EG) before and after being impregnated into a silica gel (SG) via the wet impregnation method. The AADES/SG adsorbents were evaluated for CO2 sorption performance using an automated gas sorption analyzer at 100% CO2 loading and thermogravimetric analysis (TGA) at flue gas conditions (15% CO2/85% N2). Findings show the basicity and the nitrogen content (N%) of AADES/SG were increased as Arg was added and DES/AADES functional group peaks (amino, hydroxyl, alkyl groups) were observed after the impregnation. The CO2 sorption of 16.0 mg/g at 25 °C and 1 atm was achieved by 30% Arg-EG(1:8)/SG followed by 30% ChCl-EG-Arg (1:2:0.1)/SG (14.8 mg/g) and 30% ChCl-EG/SG(1:2) (14.5 mg/g) using an Autosorb iQ2 instruments with 100% CO2 loading. The CO2 uptake was increased almost linearly with increasing pressure and decreased with increasing temperature. The Arg-EG(1:8)/SG shows the highest selectivity toward CO2 than other sorbents with 8.10 mg/g adsorption for 1 h at 15% CO2 loading at 25 °C with higher thermal stability and surface area. Considering environmental, technological, and economic viewpoints, the Arg-EG(1:8)/SG can be explored more as a potential solid sorbent for CO2 capture.

Renewable deep eutectic solvents pretreatment improved the efficiency of anaerobic digestion by lignin extraction from willow

Lignin extraction from lignocellulosic biomass can enhance its bioconversion efficiency, whilst the recovered lignin can provide added economic value. This study comprehensively investigated the impacts of short-chain carboxylic acid-based deep eutectic solvents (DESs) pretreatments on lignin extraction from willow and assessed subsequent biomethane production through anaerobic digestion. Process parameters (including the DESs type, molar ratios of DESs components, temperature and reaction time) in the DESs pretreatments of willow for lignin extraction were optimized using the central composite surface response methodology. Results showed that lactic acid-based DES pretreatment outperformed acetic acid and propionic acid-based DES pretreatments in terms of lignin removal efficiency and methane production. Under the optimal conditions (choline chloride:lactic acid with a molar ratio of 1:10 at 160 °C for 15 min) lactic acid-based DES pretreatment retained over 94% of the glucan content in the raw willow whilst achieved the highest lignin removal of 80%. The recovered lignin showed a purity of above 81%. Compared with the biomethane production of 89.9 mL/g total solid from raw willow, the biomethane production significantly increased by 36.3% after the lactic acid-based DES pretreatment. The optimal condition reduced the digestion time from 22 to 10 days. The overall energy conversion efficiency of 62.7% demonstrated that lactic acid-based DES pretreatment of lignocellulose could be a promising method to co-produce renewable gaseous fuels and lignin in a sustainable approach.

Lactic acid-based deep eutectic solvents and activated carbon for soap removal from crude biodiesel

Lactic acid-based deep eutectic solvents and activated carbon for soap removal from crude biodiesel

Cellulose esterification with carboxylic acid in deep eutectic solvent pretreatment inhibits enzymatic hydrolysis

Avicel cellulose was pretreated using two commonly used carboxylic acid-based deep eutectic solvents, i.e., choline chloride-lactic acid and choline chloride-formic acid. The pretreatment process resulted in the formation of cellulose esters with lactic acid and formic acid, which was confirmed by infrared and nuclear magnetic resonance spectra. Surprisingly, the esterified cellulose led to a significant decrease in the 48-h enzymatic glucose yield (≥75%) compared to raw Avicel cellulose. Analysis of changes in cellulose properties caused by pretreatment, including crystallinity, degree of polymerization, particle size and cellulose accessibility, contradicted the observed decline in enzymatic cellulose hydrolysis. However, removing the ester groups through saponification largely recovered the reduction in cellulose conversion. The decreased enzymatic cellulose hydrolysis by esterification may be attributed to changes in the interaction between cellulose-binding domain of cellulase and cellulose. These findings provide valuable insights into improving the saccharification of lignocellulosic biomass pretreated by carboxylic acid-based DESs.

An environmentally friendly method for extraction of cobalt and molybdenum from spent catalysts using deep eutectic solvents (DESs).

There has been a substantially increasing demand for energy critical elements (ECEs) in recent years as energy-related technology has advanced rapidly. Spent catalysts are known as potential sources of ECCs such as Ni, Co, Mo, W, V, and rare earth elements. This study developed a novel environmentally friendly process for recovering cobalt and molybdenum from spent hydroprocessing catalysts using deep eutectic solvents (DESs). DESs based on p-toluenesulfonic acid achieved high metal extraction at 100°C and a pulp density of 20g/L for 48h which 93% of cobalt and 87% of molybdenum were dissolved. FT-IR and H-NMR analyses were conducted to determine whether hydrogen bonds form between p-toluenesulfonic acid-based DES components. Leaching kinetic models were also developed for DES systems. The experimental results were well-matched with the shrinking core models. The leaching controlling step of DES-1 was determined to be the diffusion through the product layer based on kinetic studies, with an activation energy of 22.56kJ/mol for Co and 29.34kJ/mol for Mo in DES-1. Similarly, the mixed control reaction with an activation energy of 38.09kJ/mol for Co and 31.48kJ/mol for Mo in DES-2 was found to control the leaching kinetic mechanism of the DES-2 sample.