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Deep eutectic solvents have emerged in green chemistry only seventeen years ago and yet resulted in a plethora of publications covering various research areas and diverse fields of application. Deep eutectic solvents appear as promising alternatives to conventional organic solvents due to their straightforward preparation using highly accessible and natural compounds. They display also high tunability. Here we present the classification and preparation methods of deep eutectic solvents. We detail their physicochemical properties such as phase behavior, density, viscosity, ionic conductivity, surface tension, and polarity. Properties are controlled by the choice of the forming compounds, molar ratio, temperature, and water content.

Hydrogen peroxide (H2O2) is an important chemical in synthetic chemistry with huge demands. Photocatalytic synthesis of H2O2 via oxygen reduction and water oxidation reactions (ORR and WOR) is considered as a promising and desirable solution for on‐site applications. However, the efficiency of such a process is low due to the poor solubility of molecular oxygen and the rapid reverse reaction of hydroxyl radicals (•OH) with hydrogen atoms (H). Here, a strategy is proposed to boost the H2O2 evolution via oxidation of water by employing a H acceptor (A, nitrocyclohexane), an •OH mediator (M, dioxane), and a photocatalyst (CdS nanosheets). While •OH radicals are stabilized by dioxane to produce ketyl radicals prior to the formation of H2O2, H atoms are effectively utilized in the generation of cyclohexanone oxime, an important intermediate in the production of Nylon 6. The system displays a rapid kinetic accumulation of H2O2 (0.13 min−1) to a high concentration (6.6 mM). At optimum reaction conditions, a high quantum efficiency (16.6%) and light‐to‐chemical conversion efficiency (4.9%) can be achieved under 410 nm irradiation. Photocatalytic partial water oxidation promoted by a hydrogen acceptor (A) and a hydroxyl mediator (M) couple on CdS nanosheets. While the photogenerated •OH radicals can be stabilized by M to produce ketyl radicals prior to the formation of H2O2, H atoms are transferred to A. This strategy enables a rapid evolution of H2O2 with a high quantum efficiency (16.6%) under visible light irradiation.

Enteric methane (CH[sub.4]) emissions from ruminants contribute significantly to agricultural greenhouse gases. Anti-methanogenic feed additives (AMFA), such as Asparagopsis spp. and 3-nitrooxypropanol (3-NOP), reduce CH[sub.4] emissions by inhibiting methanogenic enzymes. However, CH[sub.4] inhibition often leads to dihydrogen (H[sub.2]) accumulation, which can impact rumen fermentation and decrease dry matter intake (DMI). Recent studies suggest that co-supplementation of CH[sub.4] inhibitors with alternative electron acceptors, such as phloroglucinol, fumaric acid, or acrylic acid, can redirect excess H[sub.2] during methanogenesis inhibition into fermentation products nutritionally beneficial for the host. This review summarizes findings from rumen simulation experiments and in vivo trials that have investigated the effects of combining a CH[sub.4] inhibitor with an alternative H[sub.2] acceptor to achieve effective methanogenesis inhibition. These trials demonstrate variable outcomes depending on additive combinations, inclusion rates, and adaptation periods. The use of phloroglucinol in vivo consistently decreased H[sub.2] emissions and altered fermentation patterns, promoting acetate production, compared with fumaric acid or acrylic acid as alternative electron acceptors. As a proof-of-concept, phloroglucinol shows promise as a co-supplement for reducing CH[sub.4] and H[sub.2] emissions while enhancing volatile fatty acid profiles in vivo. Optimizing microbial pathways for H[sub.2] utilization through targeted co-supplementation and microbial adaptation could enhance the sustainability of CH[sub.4] mitigation strategies using feed additive inhibitors in ruminants. Further research using multi-omics approaches is needed to elucidate the microbial mechanisms underlying the redirection of H[sub.2] toward beneficial fermentation products during enteric methanogenesis inhibition. This knowledge will help guide the formulation of novel co-supplements designed to reduce CH[sub.4] emissions and improve energy efficiency for sustainable livestock production.

Using the basic principle of construction between a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD), four bio-based deep eutectic solvents (DESs) were prepared in a 1:2 molar ratio of HBA:HBD. 2,3-Dihydroxypropyl-1-triethylammonium chloride ([C9H22N+O2]Cl婨 ) was synthesized from raw glycerol and used as an HBA. Lactic acid, urea, pure glycerol, and ethylene glycol were selected as HBD. Attempts to prepare DESs, using citric acid and benzoic acid as HBDs, were unsuccessful. All these DESs were characterized using FTIR and NMR techniques. Besides, physicochemical parameters such as pH, viscosity, density, and melting point were determined. The behavior of these DES to fractionate olive pomace was studied. Lignin recovery yields spanned between 27% and 39% (w/w) of the available lignin in olive pomace. The best DES, in terms of lignin yield ([C9H22N+O2]Cl婨 -lactic acid), was selected to perform a scale-up lignin extraction using 40 g of olive pomace. Lignin recovery on the multigram scale was similar to the mg scale (38% w/w). Similarly, for the holocellulose-rich fractions, recovery yields were 34% and 45% for mg and multi-gram scale, respectively. Finally, this DES was used to fractionate four fruit pruning samples. These results show that our novel DESs are alternative approaches to the ionic liquid:triethylammonium hydrogen sulfate and the widely used DES: choline chloride:lactic acid (1:10 molar ratio) for biomass processing

Deep Eutectic Solvents (DESs), particularly Naturally Available Deep Eutectic Solvents (NADESs), are increasingly regarded as green solvents due to their low vapor pressure, non-flammability, thermal stability, strong solvent power, and low toxicity. In line with Green Chemistry principles, the use of renewable and biocompatible components such as amino acids, lipids, and naturally derived acids enables the development of more sustainable solvent systems. This study addresses the need for environmentally safer NADESs by evaluating their physico-chemical suitability and environmental impact. Fifteen NADESs were prepared using naturally derived components and assessed for environmental safety. Biodegradability was evaluated using the OECD 301D Closed Bottle Test (CBT), while toxicity toward Raphidocelis subcapitata was examined to characterize ecotoxicological behavior. The results demonstrated that the synthesized NADESs exhibit high biodegradability levels and low toxicity toward microalgae. Toxicity control indicated no significant inhibition of microbial activity during biodegradation, suggesting favorable environmental compatibility. Overall, the findings indicate that the NADESs represent more sustainable solvent alternatives with low toxicological profiles. However, the potential role of these compounds in enhancing eutrophication processes cannot be excluded and warrants further investigation.

Background: Blackcurrant (Ribes nigrum L.) leaves are valuable sources of bioactive compounds, including phenolic acids, flavonoids, and tannins, which contribute to their potent antioxidant, anti-inflammatory, and antimicrobial properties. Objectives: The overall aim of this study was to investigate the antimicrobial potential of extracts rich in bioactive compounds from blackcurrant leaves prepared in natural deep eutectic solvents (NaDESs). The objectives included the optimization of polyphenols extraction in NaDESs, characterization of the phytochemical composition by liquid chromatography–mass spectrometry (LC-MS), explanation of the chemical interactions between solvent systems and the main bioactive compound (chlorogenic acid) by molecular dynamics simulations, and evaluation of biological efficacy through antimicrobial tests. Methods: Two hydrogen-bond acceptors (HBAs) and three hydrogen-bond donors (HBDs) were tested. The experimental design included variables such as the HBA:HBD molar ratio, water percentage, extraction time, and extraction techniques used, specifically ultrasound-assisted extraction (UAE) and ultra-turrax extraction (UTE). The evaluated responses included the total polyphenol content, total flavonoid content, and total antioxidant activity. Antimicrobial assays were performed on four Gram-positive and three Gram-negative bacterial species, as well as one fungus, Candida albicans. Results: The extracts obtained by UAE showed higher concentrations of polyphenols and increased antioxidant potential. LC-MS analysis revealed the predominant presence of chlorogenic acid. The extracts showed significant activities against Gram-positive bacteria and Candida albicans. Conclusions: This study highlights the antioxidant and antimicrobial potentials of blackcurrant leaves extracts prepared in NaDESs, confirming that this type of solvent enhances polyphenols extraction and offers perspectives for new therapeutic formulations.

The development of electric vehicles and portable electronic devices has increased the use of lithium-ion batteries, resulting in increased battery waste. Currently, efficient, and environmentally friendly lithium-ion battery recycling technology is needed to reduce environmental pollution due to LIB waste. Deep eutectic solvent (DES) is attracting attention as an environmentally friendly solvent that can be used in recycling processes. This research aims to obtain Co and Mn elements from recycled lithium-ion batteries using the leaching method using DES. In the DES synthesis process, ChCl is used as a hydrogen bond acceptor (HBA) and oxalic acid as a hydrogen bond donor (HBD) with an HBA/HBD ratio (1/1). Deep eutectic solvent ChCl: oxalic acid is used as a solvent in the process of leaching valuable metals from used lithium-ion batteries. The effect of temperature and time will be investigated on the leaching recovery. These variables include temperature variations (30°C, 55°C and 80°C), time variations (1,3,5,7, and 10 minutes) and S/L 1gr/50ml with a stirring speed of 1000rpm. The results showed that the leaching recovery of Co was 62.88% and Mn was 43.56% at a temperature of 80°C for 10 minutes.

Reducing methane emission from ruminant animals has implications not only for global environmental protection but also for efficient animal production. Tea saponins (TS) extracted from seeds, leaves or roots of tea plant are pentacyclic triterpenes. They have a lasting antiprotozoal effect, but little effect on the methanogen population in sheep. There was no significant correlation between the protozoa counts and methanogens. The TS decreased methanogen activity. It seems that TS influenced the activity of the methanogens indirectly via the depressed ciliate protozoal population. The TS addition decreased fungal population in the medium containing rumen liquor in in vitro fermentation, but no such effect was observed in the rumen liquor of sheep fed TS. Tea saponins had a minor effect on the pattern of rumen fermentation and hence on nutrient digestion. When added at 3 g/day in diets, TS could improve daily weight gain and feed efficiency in goats. No positive associative effect existed between TS and disodium fumarate or soybean oil on methane suppression. Inclusion of TS in diets may be an effective way for improving feed efficiency in ruminants.

Three ternary mixtures composed by choline chloride (ChCl), ethylene glycol (EG), and a second hydrogen bond donor (HBD) as ethanol (A), 2-propanol (B), and glycerol (C) were studied in terms of composition related to the band gap energy (BGE). A Design of Experiments (DoE) approach, and in particular a Simple Lattice three-components design, was employed for determining the variation of the BGE upon the composition of each system. UV-VIS analysis and subsequent Tauc plot methodology provided the data requested from the DoE, and multivariate statistical analysis revealed a drop of the BGE in correspondence to specific binary compositions for systems A and B. In particular, a BGE of 3.85 eV was registered for the mixtures ChCl/EtOH (1:1) and ChCl/2-propanol (1:1), which represents one of the lowest values ever observed for these systems.

The development of deep eutectic solvent (DES) as a green medium and catalyst for sustainable organic synthesis is expanding due to environmental consciousness. DES components are inexpensive, easy to synthesize, non-toxic, biodegradable, and have tunable physicochemical properties. In this study, DESs were formed by a mixture of choline chloride (ChCl) as a hydrogen bond acceptor (HBA), while oxalic acid, glycerol, and urea acted as hydrogen bond donors (HBD). The formed DESs were then characterized by FTIR and their physicochemical properties. DES was applied as a catalyst in the esterification reaction of hydroxyphenylglycine (HPG) to produce hydroxyphenylglycine methyl ester (HPGME), an intermediate material for beta-lactam antibiotics. The result demonstrated that using DES consisting of ChCl-oxalic acid (1:1) could produce HPGME with a yield of 40%. However, further research is essential to investigate the optimum reaction condition, such as the composition of added DES, reaction time, and temperature to obtain a higher yield of HPGME.