Effect Of Deep Eutectic Solvents Research Articles

Examining the Effectiveness of Deep Eutectic Solvents in Removal of Sulfur from Fuel Oil: A Mini Review

AbstractThe global demand for cleaner and more sustainable energy sources has stimulated extensive research into advanced technologies for sulfur removal from fossil fuels. Sulphur compounds in fuels contribute to air pollution, acid rain, and environmental degradation, underscoring the urgency of efficient desulfurisation methods. Deep eutectic solvents (DESs) have emerged as environmentally friendly candidates for sulphur removal from fuels. This review provides an overview of recent advancements in utilising DESs for desulfurisation processes, highlighting their sustainable and economically viable features. The manuscript begins with an introduction to the pressing need for clean fuels. It also emphasises the unique properties of DESs, such as low toxicity, biodegradability, and tunability, making them well-suited for sulphur extraction. A brief discussion on the classification and synthesis of DESs contextualises the review. Additionally, an overview of the effects of sulphur on the environment is presented. This review systematically categorises DESs used for desulfurisation into five distinct groups: DESs containing transition metal salts, sulfones, glycols, aromatic compounds, and organic acids. Each category is thoroughly discussed, examining their respective applications and effectiveness in desulfurisation processes. Towards the end, the review addresses current challenges and prospects in the field, including scaling up DES-based processes and enhancing efficiency through catalysts and synergistic approaches. Graphical Abstract

Synergistic Effect of Deep Eutectic Solvent and Zinc Oxide in Transesterification of Dimethyl Terephthalate for the Synthesis of Alkyl Terephthalate Esters

Synergistic Effect of Deep Eutectic Solvent and Zinc Oxide in Transesterification of Dimethyl Terephthalate for the Synthesis of Alkyl Terephthalate Esters

Effect of Deep Eutectic Solvents Based on Choline Chloride as Extractants on the Separation of the 1-Butanol–1-Butyl Formate System: Experimental Study and Comparative Analysis

Effect of Deep Eutectic Solvents Based on Choline Chloride as Extractants on the Separation of the 1-Butanol–1-Butyl Formate System: Experimental Study and Comparative Analysis

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.

Comparative analysis of photo-fermentation hydrogen production from pretreated corn stover by deep eutectic solvents

To compare the pretreatment effect of deep eutectic solvents (DESs) on corn stover, three types of DESs (acid, neutral, and alkaline) were used to pretreat corn stover, and their effects on lignin removal were investigated. Then the performance of photo-fermentation hydrogen production (PFHP) using DESs pretreated corn stover was compared and analyzed. The results showed that acid DESs had the best lignin removal efficiency, and the lignin removal percentages of choline chloride/formic acid (ChCl/Fac) and choline chloride/oxalate (ChCl/Oac) were 64.7% and 65.6%, respectively. The alkaline DESs had the second highest removal of lignin, while the neutral DESs had a poor effect on lignin removal. The comparison of hydrogen production indicated that the corn stover pretreated with ChCl/Oac had the best hydrogen production effect. In conclusion, the DESs pretreatment can obviously remove the lignin in corn stover, and then improve the hydrogen production capacity and efficiency of photo-fermentation, which provides a potential pretreatment method for the efficient utilization of straw biomass.

Optimizing green approach to enhanced antioxidants from Thai pigmented rice bran using deep eutectic solvent-based ultrasonic-assisted extraction

Deep eutectic solvents (DES) have garnered significant attention as extraction media owing to their commendable attributes of being environmentally sustainable and the inherent adaptability of DES's versatile physical and chemical characteristics. The present study investigated the effects of deep eutectic solvents on the total contents of anthocyanin, phenolic, and flavonoids, as well as the antioxidant activity of Thai pigmented rice bran extract. The optimal extraction parameters for deep eutectic solvent-based ultrasonic-assisted extraction (DES-UAE) were also determined using the response surface methodology (RSM). The optimal conditions for the extraction of anthocyanins and other antioxidants from pigmented rice bran using a deep eutectic solvent were choline chloride: ethylene glycol (Ch:Eg) at a 1:2 ratio, mixed with 20 % water as a solvent. The ultrasonic-assisted extraction (UAE) at 37 kHz of frequency, 50 °C of temperature, 40 min of extraction time, and a 1:6 g/mL of solid-to-solvent ratio yielded a total anthocyanin content of 4.55 ± 0.09 mg C3G/g DW, a total phenolic content of 26.49 ± 0.62 mg GAE/g DW, a total flavonoid content of 6.57 ± 0.55 mg QE/g DW, and a percent inhibition of DPPH radical of 77.83 ± 1.51. By comparing the antioxidant content that was extracted from three cultivars of pigmented rice, it was found that Leum Pua black rice bran provided significantly higher antioxidant content compared to Hom Nin purple rice bran and Mali Dang red rice bran. This research suggests an achievable, eco-friendly, and effective method for preparing high-quality, consumer-safe Thai rice bran as a raw material for nutraceuticals.

Effect of Deep Eutectic Solvents on the Activity and Stability of Cellulases and Pectinases

Effect of Deep Eutectic Solvents on the Activity and Stability of Cellulases and Pectinases

Extraction of Chitin from Giant Tiger Prawn (Penaeus monodon) Shrimp Shell Using Deep Eutectic Solvents and Citric Acid

Chitin, a natural biomass resource, has shown great promise for a wide range of applications because of its high bioactivity. This study evaluated the effectiveness of deep eutectic solvents (DESs) mixed with citric acid as a method for extracting chitin from the shells of giant tiger prawn shrimps (Penaeus monodon). The purity and physicochemical properties of the extracted chitin were compared with those obtained using the traditional chemical extraction method and commercial chitin. The results showed that the highest chitin purity (99.22%) was achieved when choline chloride-glycerol (ChCl–Gl) was used in a 1:2 molar ratio with a citric acid content of 5% w/v (CG2-5%). Additionally, the extracted chitin had a molecular weight of 3.75 × 105 Da and a crystallinity index of 81.34%, which was slightly higher than that of chitin extracted using the conventional method (3.24 × 105 Da and 73.59%). However, there was no significant difference between chitin extracted by CG2-5% and commercial chitin. This suggests that the structure of the biopolymer remained intact following the CG2-5% extraction process. The α-chitins in tiger prawn shrimp shells, as confirmed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction Analysis (XRD), are analogous to commercial shrimp chitin. These results, achieved without employing potentially harmful chemicals, demonstrate that CG2-5% can efficiently enhance chitin extraction from diverse raw biomass sources without jeopardizing the polymer's structural stability.

Effect of deep eutectic solvents on vulcanization and rheological behaviors of rubber vulcanizates

Deep eutectic solvents (DESs) are able to promote vulcanization of rubbers while the mechanisms remain unclear. Herein 4-methyl-5,7-dihydroxycoumarin (DHMC) as hydrogen bond donor (HBD) was used to synthesize DES by reaction with tetrabutylammonium bromide (TBAB) as hydrogen bond acceptor (HBA). The effects of DHMC, TBAB and DES on vulcanization of natural rubber (NR) and isoprene rubber (IR) were studied. It is shown that DES could participate in crosslinking network and adjust crosslinking density (vc) of the vulcanizates through physical and chemical interactions with NR non-rubber components, zinc oxide (ZnO) activator and N-cyclohexyl-2-benzothiazolesulfenamide (CZ) accelerator. Furthermore, DES influences linear and nonlinear rheological responses and mechanical behaviors of NR vulcanizates. The NR vulcanizates cured at 120 °C with 0.1–0.3 phr (part per hundred parts of rubber) DES exhibit higher tensile strengths and lower vc in comparison with the control one cured at 140 °C, which is assigned to the more homogenous crosslinking network in the former. This work provides an effective way to modulate the crosslinking network to produce high-strength vulcanizates at lowered vulcanization temperatures and ZnO amount, which is beneficial for the preparation of rubber products with high strengths and low hysteresis energies.

Effects of deep eutectic solvents on the activity and stability of enzymes

From introduction of deep eutectic solvents (DESs) in 2003 and because of their unique properties such as low melting points, safety, low cost of raw material, availability, sustainability, and biodegradability, DESs are garnering attention in various fields of technology, particularly biocatalysis. Progress in these fields has illustrated that enzymes are able to maintain and even improve their activity and stability in DES-based media. Consequently, they became promising alternatives as developed solvents, cosolvents, or additives over conventional organic solvents. The current study reviewed the recent progress of the effects of various DESs on the function and stability of different enzymes.

Effectiveness of deep eutectic solvents for light oil recovery through spontaneous imbibition

With the rise in demand for energy, comes the need to extract oil from not only primary and secondary stages, but also from tertiary recovery methods to keep up with the current market. Enhanced oil recovery (EOR) has become more prevalent within maturing reservoirs. Ionic liquids (IL) were highly regarded for chemical EOR until researchers raised concerns about their expensive cost, toxicity, and environmental impacts. Recently, deep eutectic solvents (DES) were discovered as a potential replacement for ILs due to their non-toxic nature, being biodegradable, non-flammable, and cheaper. In this study, the effectiveness of DES is investigated by observing its ability to promote oil recovery through wettability alteration. Spontaneous Imbibition tests along with emulsion and thermogravimetric tests (TGA) are used to achieve the objectives. Results indicated that both DESs can recover oil that was not recoverable using brine only. At higher temperatures, the effectiveness of DES was higher, which allowed for more oil to be imbibed out. The effect of concentration suggested that at high concentrations, DESs exhibit self-destructive properties by increasing interfacial tension (IFT), which reduced the imbibition rate and recovery factor. TGA studies indicate that the thermal stability of DESs is highly dependent on the thermal stability of their hydrogen bond donor (HBD).

Effects of deep eutectic solvents on the biotransformation efficiency of ω-transaminase

ω-transaminase (ω-TA) shows a significant promising in the synthesis of chiral amines. However, the poor activity of ω-TA in buffer water solution limits its application in industry, so green and economic methods adopted to improve ω-TA activity still face challenges. Here, deep eutectic solvents (DES) were used as the co-solvent to improve the catalytic activity of ω-TA. The results have shown that DES (ChCl: Urea 1:1) was the most suitable co-solvent for increasing the biotransformation efficiency of the ω-TA in nine different choline chloride-based DESs. The optimal enzymatic activity was achieved at 40 ℃, in 10 vol% DES and pH 8. The specific activity of ω-TA in DES was increased by 3.9 times due to the reinforced interactions between DES and enzyme. The kinetic analysis of transaminase showed that DES enhanced affinity of ω-TA for 1-(R)-PEA and pyruvate to increase by 1.93 and 1.63 times respectively compared with the control. Molecular docking shows that urea acted as a proton donor and a receptor during the enzymatic reaction, the docking binding energy increases to 3.21 and 3.59 kcal/mol, promoting the transamination reaction. DES can significantly improve the catalytic activity of ω-TA, which has broad development prospects in the field of green and efficient synthesis of pharmaceutical and natural product intermediates.

Acidic deep eutectic solvent assisted mechanochemical delignification of lignocellulosic biomass at room temperature

Lignocellulosic biomass is the most abundant natural polymer on Earth, but the efficient fractionation and refinery of all its components remain challenging. Acidic deep eutectic solvents refining is a promising method, while it is likely to cause lignin condensation and carbohydrates degradation, especially at server operation conditions. Here we propose the use of acidic deep eutectic solvent (DES), choline chloride/p-toluenesulfonic acid assisted mechanochemical pretreatment (DM) for efficient lignocellulose fractionation at mild condition. Four representative lignocellulose, wheat straw, moso bamboo, poplar wood and pine wood were selected at varied milling time (3, 6 h) to assess the fractionation ability of this strategy. This DM pretreatment demonstrated a rather high cellulose retentions (∼90 %) and extent of delignification for wheat straw and bamboo biomass, which corresponds to a high extent of enzymatic hydrolysis (∼75.5 %) for sugar platform pursuing. The extracted lignin showed rather high content of β-O-4′ leakages due to the swelling effect of deep eutectic solvent and mild operation conditions. This work provided a promising strategy to fractionate lignocellulose using deep eutectic solvents with the goal of simultaneous cellulose hydrolysis and reactive lignin obtaining that is usually difficult to realize using traditional chemical fractionation approach.

Combined Effects of Deep Eutectic Solvents and Pulsed Electric Field Improve Polyphenol-Rich Extracts from Apricot Kernel Biomass

Apricots are one of the most important fruits in the Mediterranean region for both their nutritional and economic value. They are widely cultivated and consumed fresh or dried or are used in the food industry for the production of jams, juices, etc. In any case, the seeds they contain constitute waste. The kernels are very rich in bioactive compounds such as polyphenols, a fact that makes them very appealing in cosmetology. However, the extraction of the bioactive compounds of apricot kernels is poorly examined. In this study, the preparation of polyphenol-rich extracts from apricot kernel biomass is discussed. To this end, a common extraction procedure with water as a solvent was employed. To enhance the extraction yield, the use of a deep eutectic solvent (DES) was examined. In addition, the use of pulsed electric field (PEF) either as a standalone extraction method or as a complementary step was also examined. According to the results, it was evident that when PEF was applied before the extraction procedure, an increase of 88% in the total polyphenol content (TPC) was recorded. Likewise, the use of a glycerol:choline chloride (2:1, w/w) DES increased the TPC by ~70%. When the two approaches were combined, a 173% increase was recorded. According to the above, it can be concluded that apricot kernel biomass is a very good source of polyphenols, especially using the proposed extraction procedure.

Enhancing effect of choline chloride-based deep eutectic solvents with polyols on the aqueous solubility of curcumin–insight from experiment and theoretical calculation

The development of green solvents for enhancing aqueous solubility of drug curcumin remains a challenge. This study explores the enhancing effect of deep eutectic solvents (DESs) on the aqueous solubility of curcumin (CUR) via experiment and theoretical calculation. Choline chloride-based DESs with polyols 1,2-propanediol (1,2-PDO), 1,3-propanediol, ethylene glycol, and glycerol as hydrogen bond donors were prepared and used as co-solvents. The CUR aqueous solubility increased with increasing the DESs content at temperature of 303.15–318.15 K, especially in aqueous ChCl/1,2-PDO (mole ratio 1:4) solutions. The positive apparent molar volume values and reduced density gradient analysis confirmed the existence of strong interactions between CUR and solvent. The van der Waals interactions and hydrogen bonding coexisted in DESs monomer retained the stability of DESs structure after introducing CUR. Moreover, the lower interaction energy of DESs⋅⋅⋅CUR system than that of the counterpart DESs further proved the strong interaction between CUR and DESs. The lowest interaction energy of ChCl/1,2-PDO⋅⋅⋅CUR system indicated that this system was the most stable and ChCl/1,2-PDO was promising for CUR dissolution. This work provides efficient solvents for utilizing curcumin, contributing to a deep insight into the interactions between DES and CUR at the molecular level, and the role of DESs on enhancing drugs solubility.

Liquid-liquid equilibrium experiment and mechanism analysis of menthol-based deep eutectic solvents extraction for separation of fuel additive tert-butanol

Deep eutectic solvents (DESs) were synthesized using menthol as hydrogen bond acceptor (HBA) and different carbon chain carboxylic acids as hydrogen bond donors (HBD). The liquid equilibrium (LLE) experiment was used to determine the distribution coefficient (β) and slectivity (S) at standard atmospheric pressure and temperature. The effect of DESs on the separation efficiency was discussed by changing the proportion. Non-random two fluid (NRTL) model was used to correlate the experimental data. The molecular dynamics (MD) simulation method was used to investigate the micro mechanism of the extraction process. The results show van der Waals force plays a leading role in the interaction between solvents and tert-butyl alcohol (TBA) and week force with water. Compared with experimental and simulation results, the interaction between DESs and TBA would also be affected by the change of the number of HBD carbon chains, and DESs with decanoic acid as HBD has the best separation effect, which verifies the feasibility of separating high alcohol compounds from water by DESs and then treating them by DESs.

Effect of deep eutectic solvents on the biocatalytic properties of β-glucosidase@ZnOFe nano-biocatalyst

In this work, we investigate the use of aqueous deep eutectic solvents (DESs) consisting of different hydrogen bond acceptors (choline chloride, ammonium salts or betaine) and hydrogen bond donors (amines, sugars and alcohols), as co-solvents in biocatalytic reactions catalyzed by a nano-biocatalyst with β-glucosidase (BGL) activity. For this purpose, β-glucosidase from Thermotoga maritima was immobilized on the surface of green zinc oxide-iron oxide nanoparticles (BGL@ZnOFe) derived from an aqueous olive leaf extract. The covalent bonding of β-glucosidase on the surface of nanoparticles was demonstrated by X-ray photoelectron spectroscopy. The effect of a wide range of DES solutions on the biocatalytic features of BGL@ZnOFe was thoroughly investigated. The concentration of DES as well as the specific combination of hydrogen bond acceptors and hydrogen bond donors had a significant impact on the hydrolytic activity of immobilized β-glucosidase. Most choline chloride and betaine-based DESs enhanced the enzymatic activity and thermal stability of BGL@ZnOFe up to 50%. The enzymatic activity of the nano-biocatalyst towards the hydrolysis of bioactive phenolic compounds depends on the nature of the DES used. Choline chloride:butylene glycol-based medium had beneficial effect on a transglycosylation reaction, such as the synthesis of salidroside, increasing the total turnover number of the biocatalytic process by 55%. This work indicates that the use of several choline chloride and betaine-based DESs can be successfully employed as green co-solvents in various hydrolytic and synthetic biocatalytic processes.

Ternary Liquid-Phase Equilibria of an Azeotropic Mixture (Heptane + Isopropyl Alcohol) with Deep Eutectic Solvents

The present study reports the result of the measurement and analysis of the solubility curve and tie-line data of four ternary systems containing heptane–isopropyl alcohol azeotrope mixtures and deep eutectic solvents (DESs) at T = 298.2 K and p = 0.1 MPa. This investigation is aimed to evaluate the efficiency of the prepared DESs as extractants in the separation of the heptane–alcohol azeotropic mixtures through liquid–liquid extraction (LLE) processes. In this study, four choline chloride-based DESs were prepared by a heating process. Two hydrogen bond donor (HBD) compounds (i.e., ethylene glycol and propylene glycol) were chosen in the preparation of the DESs. The solubility curves show that the effect of DESs on the immiscibility region is small. The studied systems display the type-1 LLE behavior. The measured tie-line values were adequately fitted through the nonrandom two-liquid (NRTL) thermodynamic model, and the interaction parameter values were determined. The correlation data appeared to be in good agreement with the measured tie-lie data. The extraction capacity (distribution constants and selectivities) of the studied DESs was determined. The DESs had high and similar selectivity values for the studied systems. Moreover, the distribution constants were larger than unity, indicating a favorable solvent-to-feed ratio.

Antiamoebic properties of salicylic acid-based deep eutectic solvents for the development of contact lens disinfecting solutions against Acanthamoeba

Acanthamoeba castellanii is a protist pathogen that can cause sight-threatening keratitis and a fatal infection of the central nervous system, known as granulomatous amoebic encephalitis. In this study, effects of five malonic acid and salicylic acid-based deep eutectic solvents (DES) on A. castellanii were investigated. These are salicylic acid-trioctylphosphine (DES 1), salicylic acid- trihexylamine (DES 2), salicylic acid-trioctylamine (DES 3), malonic acid-trioctylphosphine (DES 4) and malonic acid-trihexylamine (DES 5). The experiments were done by performing amoebicidal, encystment, excystment, cytopathogenicity, and cytotoxicity assays. At micromolar dosage, the solvents DES 2 and DES 3 displayed significant amoebicidal effects (P < 0.05), inhibited encystment and excystment, undermined the cell-mediated cytopathogenicity of A. castellanii, and also displayed minimal cytotoxicity to human cells. Conversely, the chemical components of these solvents: salicylic acid, trihexylamine, and trioctylamine showed minimal effects when tested individually. These results are very promising and to the best of our knowledge, are reported for the first time on the effects of deep eutectic solvents on amoebae. These results can be applied in the development of new formulations of novel contact lens disinfectants against Acanthamoeba castellanii.

Effects of Deep Eutectic Solvents on cellulosic fibres and paper properties: Green “chemical” refining

This work aims to study the effects of Deep Eutectic Solvents (DES) on cellulosic fibre structure. A focus was made on the induced fibrillation phenomena which could facilitate the further production of microfibrillated cellulose. Three DES of different pH (acid, neutral and alkaline), namely betaine hydrochloride-urea, choline chloride-urea and choline chloride-monoethanolamine, were tested. Eucalyptus and cotton pulps were used to investigate the effects of DES on both hemicelluloses and cellulose. Interestingly, cellulose was esterified during acidic DES treatment. Moreover, an internal and external fibrillation occurred with DES treatment without a great extent of modification in terms of chemical composition, crystallinity and degree of polymerisation. Compared to enzymatic hydrolysis (used as a conventional pre-treatment for cellulose microfibrillation), DES have significantly enhanced the mechanical properties of resulting papers. To conclude, DES treatment can be considered as a soft and green “chemical” refining that could be applied as a pre-treatment for cellulose microfibrillation.