Solutions Of Deep Eutectic Solvents Research Articles

Molecular Understanding of Activity Changes of Alcohol Dehydrogenase in Deep Eutectic Solvents.

Deep eutectic solvents (DESs) have emerged as promising solvents for biocatalysis. While their impact on enzyme solvation and stabilization has been studied for several enzyme classes, their role in substrate binding is yet to be investigated. Herein, molecular dynamics (MD) simulations of horse-liver alcohol dehydrogenase (HLADH) are performed in choline chloride-ethylene glycol (ChCl-EG) and choline chloride-glycerol (ChCl-Gly) at varying water concentrations. In the DES solutions, the active site was significantly constricted, and its flexibility reduced when compared to the aqueous medium. Importantly, the cavity size follows a similar trend as the catalytic activity of HLADH and as such explains previously observed activity changes. To understand the impact on the binding of the substrate (cyclohexanone), an umbrella sampling (US) setup was established to calculate the free energy changes along the substrate binding tunnel of HLADH. The US combined with replica exchange and NADH in its cofactor pocket provided the best sampling of the entire active site, explaining why the cyclohexanone binding on HLADH is reduced with increasing DES content. As different components in these multicomponent mixtures influence the substrate binding, we additionally applied the US setup to study the ability of the DES components to be present inside the substrate tunnel. The presented approach may become useful to understand enzyme behaviors in DESs and to enable the design of more enzyme-compatible and tunable solvents.

Electrochemical Characterization of Silver and Iron Ions in Choline Chloride-Ethylene Glycol DES Electrolyte

Solar energy is growing to be an important source of renewable energy in the world, and the need of a recycling process to recover the strategic materials used for this technology is crucial. A route to recover Si and Ag from end-of-life photovoltaic (PV) cells as well as scrap from PV manufacturing using a Deep Eutectic Solvent (DES) have been proposed and developed as part of the PHOTORAMA project. The suggested ionometallurgical route uses a DES solution with FeCl3 as oxidizing agent to leach silver and separate it from Si, before recovering Ag metal by electrowinning (EW) from the DES-based electrolyte.Choline Chloride (ChCl)-Ethylene Glycol (EG) DES mixtures, often referred to as ethaline, in composition 1:2 molar ratio was identified as the preferred DES-system to be used for leaching and subsequent EW. As such, the DES leachate used as electrolyte in the EW step, should ideally consist of Ag(I) and Fe(II) dissolved in the DES. The goal of this work was to carry out electrochemical characterization of the electrochemical systems and understand if the presence of soluble iron species may affect the silver deposition.Model electrolyte solutions were produced by dissolving AgCl, FeCl2, and FeCl3·6H2O in the DES mixture. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV) and chronoamperometry (CA) using a 3-electrode setup. Moreover, silver deposits were obtained by potentiostatic or galvanostatic electrolysis, and subsequently analysed by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS).Cyclic voltammograms obtained using a Pt-wire with a scan rate of 200 mV/s, show well defined Ag(I)/Ag and Fe(III)/Fe(II) electrochemical systems. The deposition of metallic Fe was found to be close to the cathodic decomposition of the DES electrolyte. High quality silver deposits were obtained by choosing optimal deposition potentials or current densities. SEM-EDS analysis of the silver deposits obtained on Pt, silver, and stainless steel (316L) substrates showed a nice, dense layer of Ag crystals with a microstructure of truncated octahedrons, with a purity of 96-98 wt%. The impurities were identified as C, O or Cl and probably stemmed from the DES electrolyte remains.Based on the electrochemical characterization of the DES systems, and the analysis of the obtained silver deposits, the concept proposed for the recovery of metals in the PHOTORAMA project was found to be suitable. Water added to the DES (up to 10 wt%), which may be stemmed from the crystal water of the oxidant added, or absorbed from air, gave improved kinetics. The presence of excess of Fe(III), which could arise from incomplete leaching reaction, had the obvious negative effect on the current efficiency of the Ag(I) reduction reaction, but had no effect on the silver morphology or purity of the obtained deposit.AcknowledgementsThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958223. The content in this publication reflects only the views of the authors. The European Commission is not responsible for any use that may be made of the information it contains. Figure 1

Deep eutectic solvents assisted laccase pretreatment for improving enzymatic hydrolysis of corn stover.

The efficient and eco-friendly removal of lignin is a critical challenge for bioethanol production from lignocellulosic biomass. Herein, we report the integration of laccase with deep eutectic solvents (DESs) for the pretreatment of corn stover to enhance the production of reducing sugars. Three betaine-based DESs were prepared and tested for their effects on the activity and stability of a bacterial laccase from Bacillus amyloliquefaciens LC02. The aqueous solution of DESs showed no adverse influence on laccase activity, and the laccase thermostability was improved in the presence of DESs. More than 95% of the laccase activity was retained in the DESs solution during the first hour of incubation at 70°C. A red shift in the fluorescence spectra was observed for the laccase in the presence of DESs, indicating conformational changes. The laccase was able to degrade a dimeric lignin model compound by cleaving its β-O-4 bond. The transformation products were identified using LC-MS. The maximal lignin removal from corn stover was achieved by pretreatment using laccase in combination with the betaine-glycerol DES, which also resulted in a yield of fermentable sugar that was 130% higher than the control. This combination strategy provides guidance on the application of laccase and DESs in the pretreatment of lignocellulosic biomass.

Deep Eutectic Solvent Supported Polymer-Based High Performance Anion Exchange Membrane for Alkaline Fuel Cells

Alkaline anion exchange membrane fuel cells (AEMFC) have gained interest due to their potential as electrochemically energy conversion devices and a competitive alternative to the more extensively studied commercialized proton exchange membrane fuel cells (PEMFCs). Nevertheless, their development impedes the limited ion conductivity, chemical and mechanical stability in an alkaline medium of anion exchange membranes (AEMs). The ionic conductivity of AEM is lower than that of a proton exchange membrane (PEM) because the mobility of hydroxide ions is inherently lower than that of protons [1]. Deep eutectic solvents (DESs) as green solvents can overcome this issue.The main idea of this research is to fabricate a deep eutectic solvent-supported polymer-based AEM for alkaline fuel cell application by electrospinning technique. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of AEM due to its water solubility, biodegradability, high fiber forming ability, non-toxicity, and high chemical and thermal stability [2]. This work aims to achieve high ionic conductivity, chemical and mechanical stability by two methods: swelling polyvinyl alcohol (PVA)-based nanofibers into DES and encapsulating DES inside the PVA-nanofibers together with optimizing fabrication methods.In this study, polymer electrolytes as potential AEMs were first prepared using the swelling method, where electrospun PVA nanofibers were fabricated via the electrospinning technique, followed by swelling in a series of DESs. To prepare the DES solutions, choline chloride (ChCl) and ethylene glycol (EG) were mixed at different molar ratios. The cross-linking of pure PVA fibers with glutaraldehyde in ethanol (see Figure 1B) and DES uptake and the presence of voids as channels for ion conduction (see Figure 1C) were successfully confirmed with a scanning electron microscopy (SEM, Crossbeam500, Zeiss). The ionic conductivity of swelled in DES PVA-based membranes were evaluated by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature and was equal to 0.336 mS/cm. The presence of DES in the membrane was confirmed with FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10): a slight C-N+ peak at 953 cm-1 from ChCl has proven interaction between PVA and DES with FTIR spectroscopy, meaning that DES is present in the fiber. In addition, the nitrogen content in the obtained membrane was determined by CHNS elemental analysis (Elemental Vario micro cube) as 3.32 wt.%.In order to overcome high weight loss in the swelling method, the encapsulation method was suggested as an alternative option, which is based on the encapsulation of DES into the PVA solution by mixing them, varying the amount of DES added, and then preparing fibers using electrospinning. Observing the morphology of DES-encapsulated PVA nanofibers with a scanning electron microscope (SEM, Crossbeam500, Zeiss), as the content of DES in the solution increased, there was an observed rise in the average diameter of the nanofibers (see Figure 1D). Encapsulation of DES in PVA nanofibers was primarily confirmed by transmission electron microscope (TEM, JEM -1400 Plus, JEOL): PVA appears lighter due to its decreased density, proving that DES is present inside the fibers. Also, the same tendency was observed with the results of FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10) as for the swelling method, meaning that DES is present in the fiber. According to CHNS elemental analysis (Elemental Vario micro cube), nitrogen content was lower than for the swelling method - 0.70 wt.%. The ionic conductivity was evaluated as 0.364 mS/cm by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature, which was almost the same as for the swelling method.As a result, very flexible and visually transparent electrospun DES-supported PVA-based AEMs were obtained via the swelling and encapsulation method.

Pressure-driven membrane processes for the recovery and recycling of deep eutectic solvents: A seaweed biorefinery case study.

Deep eutectic solvents (DES) are green alternatives for conventional solvents. They have gained attention for their potential to extract valuable compounds from biomass, such as seaweed. In this framework, a case study was developed to assess the feasibility of pressure-driven membrane processes as an efficient tool for the recovery of deep eutectic solvents and targeted biomolecules. For this purpose, a mixture composed of the DES choline chloride – ethylene glycol (ChCl-EG) 1:2, water and alginate was made to mimic a DES extraction from seaweed. An integrated separation process design was proposed where ultrafiltration-diafiltration-nanofiltration (UF-DF-NF) was coupled. UF and DF were found to be effective for the separation of alginate with an 85 % yield. DES was likewise recovered by 93 %, proving the membrane filtrations’ technical feasibility. The NF performance to separate the DES from the water, for its recycling, laid by a 45 %-50 % retention and a final concentrated DES solution of 18 %(v/v).

A green and recyclable ternary deep eutectic solvent for extracting flavonol glycoside from Ginkgo leaves: Mechanism insights based on molecular level

A novel ternary deep eutectic solvent (DES) was designed for the green and efficient extraction of flavonol glycosides (FG) from Ginkgo leaves. The DES consisted of a molar ratio of choline chloride/acetic acid/1,2-propylene glycol of 1:2:3. The optimal extraction conditions were determined to a solid-liquid ratio of 42 mg/mL, an extraction time of 11.8 h, and an extraction temperature of 51℃. The extraction yield of FG was 7.8 mg/g, which demonstrated a notable enhancement in comparison to conventional extraction. Kinetics and morphology analysis revealed that the extraction process involved considerable dissolution and diffusion of the solute. Additionally, a molecular investigation using density functional theory (DFT) indicated that the interaction between the DES and FG was primarily governed by hydrogen bonding and van der Waals force. Notably, the ternary DES exhibited stronger interactions with FG, which were the key factors for better extraction efficiency. Furthermore, efficient recovery of FG from the DES solution was also achieved, with a recovery rate of 94.63%. Moreover, the recovered DES could be reused directly at least five cycles.

Utilization of Potassium Carbonate-Ethylene Glycol as Deep Eutectic Solvent to Delignification Oil Palm Empty Fruit Bunch for Furfural and Ethanol Production

Pretreatment using Deep Eutectic Solvent (DES) was done to reduce the lignin content in oil palm empty fruit bunch (OPEFB). DES solution was prepared by combining Potassium Carbonate (K2CO3) as hydrogen bond acceptors (HBA) and Ethylene Glycol (EG) as hydrogen bond donors (HBD). This study aimed to obtain optimum conditions in the pretreatment process and determine the levels of lignin, cellulose, hemicellulose, and glucose in OPEFB. The pretreatment stage was performed at different temperature parameters, 100, 120, and 150°C, for 60 minutes to produce optimum conditions. Biomass pretreated with DES was hydrolyzed by cellulase complex to obtain glycose and xylose. The results showed that the pretreatment optimum condition value achieved with DES K2CO3:EG (1:10) at 150°C for 60 minutes was able to degrade lignin by 46,06%, hemicellulose by 4,08%, increase cellulose by 60,21%. The glucose and xylose content reached 58.48 g/l and 26.60 g/l, respectively. This sugar has potential for ethanol production from glucose and furfural production from xylose.

Development of Monoethanolamine Chloride-Ethylene Diamine Deep Eutectic Solvent for Ffficient Carbon Dioxide Capture

Deep eutectic solvents (DES) emerge as a compelling class of ionic liquids, with distinct advantages over traditional solvents, particularly in the realm of CO2 capture. In the present study, [MEACl][EDA] is synthesized across various molar ratios (1:3 to 1:10) and combined with the results of Differential Scanning Calorimetry (DSC) to identify DESs. The DESs are further characterized using Fourier Transform Infrared Spectroscopy (FTIR), and the properties and performance of the DESs with diverse water contents (30–60 wt%) are systematically studied for CO2 capture. The optimal aqueous solution is identified based on the CO2 uptake and viscosity, followed by the evaluation of the cyclic absorption experiments. Results demonstrate that 40 wt% of [MEACl][EDA] DES with (1:5) molar ratio exhibits higher CO2 uptake (22.09 wt%) and comparable viscosity (4.401 mPa·s before and 13.330 mPa·s after CO2 capture at 25 °C) compared to aqueous 40 wt% MEA (15.74 wt% CO2 capture capacity, viscosity of 3.318 mPa·s before and 8.413 mPa·s after CO2 capture), and its absorption rate is also more favorable than the aqueous MEA. Furthermore, recycling studies reveal ∼ 88 % regeneration of the aqueous DES solution at 100 °C.

Mesoporous silica-grafted deep eutectic solvent-based mixed matrix membranes for wastewater treatment: Synthesis and emerging pollutant removal performance

Abstract Nano-enhanced membrane technology and deep eutectic solvents (DESs) have demonstrated effectiveness in addressing emerging environmental pollutants. This research centers on purifying water by removing heavy metals employing membranes enhanced with mesoporous silica and DES. Various DESs, including hexanoic acid, octanoic acid, and decanoic acid, were synthesized using tetrabutylammonium bromide (TBABr) as a base. The study combined a polysulfone-based membrane with mesoporous silica, aiming for efficient indigenous crafting to remove heavy metals. Mesoporous silica was blended with the synthesized DES solution, creating diverse membranes for heavy metal separation. The study characterized these membranes using various techniques such as scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurements. Surface mapping confirmed the integration of silicon-based DES, reducing the membrane surface roughness from 4 to 1.4 nm. By adjusting the carboxylic acid chain length with TBABr and adding mesoporous silica, leaching ratios were reduced from 4.2 to 2.3%. Silica-grafted DES-based membranes exhibited a progressive increase in flux from 2.6 to 26.67 L/m2 h. The synthesized silicon-based membranes demonstrated outstanding performance, achieving rejection rates exceeding 80% for chromium and arsenic, maintaining an impressive 90% flux recovery ratio even at high flux rates. This study will envision the potential of nano-enhanced membrane technology utilizing DES for sustainable water purification and wastewater treatment applications to achieve the sustainable development goal (SDG) of clean water and sanitation (SDG-6).

Influence of Electrolyte Choice on Zinc Electrodeposition.

Zinc electrodeposition serves as a crucial electrochemical process widely employed in various industries, particularly in automotive manufacturing, owing to its cost effectiveness compared to traditional methods. However, traditional zinc electrodeposition using aqueous solutions faces challenges related to toxicity and hydrogen gas generation. Non-aqueous electrolytes such as ionic liquids (ILs) and deep eutectic solvents (DESs) have gained attention, with choline-chloride-based DESs showing promise despite raising environmental concerns. In this study, zinc electrodeposition on mild steel was investigated using three distinct electrolytes: (i) halide-free aqueous solutions, (ii) chloride-based DES, and (iii) halide-free acetate-based organic solutions. The study examined the influence of deposition time on the growth of Zn on mild steel substrates from these electrolytes using physical characterization techniques, including scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that glycol + acetate-based non-aqueous organic solutions provide an eco-friendly alternative, exhibiting comparable efficiency, enhanced crystalline growth, and promising corrosion resistance. This research contributes valuable insights into the impact of electrolyte choice on zinc electrodeposition, offering a pathway towards more sustainable and efficient processes. Through a comprehensive comparison and analysis of these methods, it advances our understanding of the practical applications of zinc electrodeposition technology.

Preparation of homogeneous lignin nanoparticles by efficient extraction of lignin and modification of its molecular structure using a functional deep eutectic solvent containing γ-valerolactone

A lignin-extractive green reaction medium consisting of choline chloride, 5-sulfosalicylic acid, and γ-valerolactone was designed. Polyphenolic lignin was obtained. The green advancement of DES processing has been enhanced.

Deep-eutectic solution adding threonine additive associating with supercritical carbon dioxide to enhance zinc electroplating characteristics

Deep-eutectic solvent (DES) was used widely as an eco-friendly and sustainable process in the zinc (Zn) electroplating in this study. Both the conventional and supercritical carbon dioxide (SC-CO2) assisted electroplating processes were employed in the Zn plating on the copper substrate, respectively. Moreover, the effects of ascorbic acid (AA), nicotinic acid (NA) and threonine (Thr) additives were also investigated systematically. The Zn coating In the XRD result, the Zn texture of (0 0 2) and (1 0 1) as the (1 0 0) gradually vanished as the increase of Thr additive. Whether the use of the additives, the hardness of the prepared Zn coating from SC-CO2 assisted process was higher than conventional counterparts by 30 %. Moreover, the corrosion current density from the potentiodynamic polarization curve tended to be more passive by 55 %, manifesting that the AA and NA additives in the SC-CO2 assisted Zn electroplating was better in anticorrosion capability comparing its counterpart without additives. The current efficiency shew SC-CO2 Zn coating with Thr additive could gain a 15 % enhancement in compared to the conventional Thr-free Zn coating, making the coating more noble. Microstructures investigations using SEM showed the absence of cracking on surface. On the cross-sectional examination using TEM, a dual dense and porous layer structure were observed. EDS analysis revealed the Cu ions dissolving in the DES solution and reacted with Zn ions to for Cu-Zn alloy compounds as well as solid solution of Cu in the Zn coating while the TEM-EDS analysis showed the existence of an extraordinary Zn(Cu) and interfacial Cu-Zn alloy dual-layers. The possible ion-diffusion induced by DES mechanism causing this dual-layer and solid solution structure during the electroplating process in the DES electroplating solution was proposed.

Investigation of alcohol-based deep eutectic solvents for inhibiting hydration in shale formations

When drilling with water-based drilling fluids, the principal causes of wellbore instability are shale hydration and swelling. There exists an imminent necessity for the development of high-performance hydration inhibitors to effectively address this issue. Within the scope of this work, four alcohol-based deep eutectic solvents (DES) derived from choline chloride were prepared as efficient hydration inhibitors. The inhibitory capabilities of these alcohol-based DES, along with traditional inhibitors such as potassium chloride and polyetheramine, were compared through tests including linear swelling, hot-rolling dispersion, capillary suction timer, and sedimentation experiments. In the alcohol-based DES solutions, the expansion heights of bentonite decreased from 7.65 mm to 3.65, 3.96, 3.89, and 4.10 mm, respectively. After hot-rolling at 80 °C, the recovery rates of shale cuttings increased from 33.62 % to 91.33 %, 84.68 %, 88.38 %, and 81.24 %, respectively. All of the alcohol-based DES demonstrated superior hydration inhibition effects. The inhibition mechanism of alcohol-based DES was drawn from a comprehensive assessments encompassing zeta potential, particle size distribution, optical microscope observation, surface tension, and X-ray diffraction measurements. The predominant mechanism responsible for the inhibition of shale hydration resided in the electrostatic and hydrogen bonding interactions between the DES and clay. Additionally, the alcohol-based DES exerted a supplementary effect by reducing water intrusion via lowering the liquid surface tension. Due to their outstanding inhibitory performance, the prepared alcohol-based DES exhibited substantial promise as high-performance hydration inhibitors in shale drilling applications.

Molecular dynamic (MD) simulation and density function theory (DFT) calculation relevant to green leaching of metals from spent lithium-ion battery cathode materials using glucose-based deep eutectic solvent (DES)

Deep eutectic solvents (DES), as environmentally-friendly solvents, have shown potential for recovering metals in the cathodes of spent lithium-ion batteries (LIBs). This study employed a glucose-based DES of choline chloride to recover cobalt, manganese, nickel, and lithium from LIB cathode materials, optimizing temperature and time parameters in the range of 60–110 °C and 2–24 h for leaching the cathode materials. The highest metal recoveries were observed between 60 and 110 °C, with 82.4% for Ni, 94.2% for Co, 97.6% for Ni, and 93.7% for Li after 24 h of leaching at 100 °C. The Co, Mn, Ni, and Li recoveries in the DES solution increased with time at 100 °C. UV–visible spectroscopy analysis investigated the leaching mechanisms for cathode metals, confirming that the spent LIBs leaching in DES (ChCl:G) is not completely associated with the reduction of cobalt. It appears that other metal ions, such as Li, Mn, and Ni, form complexes with chloride ions originating from the choline chloride agent. The results of the MD simulation show that hydrogen of the OH in choline chloride has a very strong attractive interaction with the Cl− ion. Also, H atoms of OH groups in glucose molecules interact considerably with the chloride ion of choline chloride. In addition, all H atoms of OH groups in glucose form hydrogen bonds with O5 of the glucose. All metal ions, including Co3+, Li+, Mn2+, and Ni2+, have very strong electrostatic interactions with the Cl− of the choline chloride molecule. The MD calculations show that metal ions are complexed with some oxygen atoms of the glucose molecule. Results show that the choline chloride molecule (via Cl− ion) and glucose molecule (via oxygen atoms) play a significant role in the leaching of metal ions from LIBs via electronegative atoms. Another finding is that the molecules of choline chloride and glucose have no selectivity towards the leaching of ions, which agrees with the experimental results, so all ions are almost 100% extracted.

Malic acid-based deep eutectic solvent and its application in Insulin's structural stability

Deep eutectic solvents (DESs) and Ionic Liquids (ILs) have been recently used as a solvent for insulin delivery via subcutaneous, transdermal, oral, and nasal ways. However, due to their high viscosity, DESs are usually impractical for delivery applications in their pure solution. The addition of water decreases the viscosity of DESs, but it can also influence the structural stability of the proteins. Hence, DES-water solutions and their effect on insulin's structural stability need to be investigated. In this study, molecular dynamics simulations on insulin dimer in DES consisting of malic acid and choline chloride (MA-ChCl) with varying amounts of water were performed. Insulin is strongly stabilized in the DES and its aqueous solutions as compared to water. However, in the DES solutions with 50 % and 75 % water content, malic acid was observed to interact readily with insulin dimer and its binding site, causing the separation of the two monomers. Therefore, while the insulin dimer is stable in the DES with low water content, in the presence of higher amounts of water it is destabilized and the monomers are separated. Considering that insulin's active form is monomeric, and the decomposition of insulin into monomers before reaching the bloodstream can increase the pharmacokinetics of insulin delivery, the use of the aqueous DES for rapid insulin delivery is highly relevant.

CO2 absorption and desorption performance by ChCl-MEA-PZ deep eutectic solvent aqueous solutions

With the increasingly serious climate problem, carbon dioxide capture has been paid more and more attention. Deep eutectic solvent (DES), which is environmentally friendly and simple to synthesize, has attracted considerable attention as a new type of carbon dioxide absorbent. Choline chloride (ChCl) - monoethanolamine (MEA) - piperazine (PZ) DESs were prepared. The chemical reaction between ChCl-MEA-PZ DES and CO2 was confirmed to be the zwitterionic mechanism by NMR spectrum analysis. The influences of molar ratio between ChCl, MEA and PZ, gas–liquid flow rates, water content and CO2 concentration on CO2 absorption character were studied by a microchannel reactor. Under appropriate conditions, CO2 absorption efficiency could reach 99.95 %. The addition of promoter PZ could significantly enhance CO2 absorption performance. Additionally, desorption energy consumption of DES solution after CO2 saturation is lower than that of the standard 30 wt% MEA solution, which proves process friendliness of the DES. This study not only provides technical support but also sheds light on the potential applications of DESs in CO2 capture.

Super concentrated HCl in a deep eutectic solvent as media for the integrated leaching and separation of metals from end-of-life lithium-ion batteries

Recycling spent lithium-ion batteries is vital to ensure the recovery of added-value resources and minimize environmental impact. Herein, an integrated and efficient process is developed for metal recovery from spent cathode powder combining both leaching and transition metal separation in one step. A hydrophobic deep eutectic solvent (DES) is proposed as a HCl super concentrator for the one-pot leaching of cathodes from spent lithium-ion batteries and simultaneous Ni(II) precipitation. The DES composed of decanoic acid and trioctylphosphine oxide can super concentrate HCl, 2.2-folds more than the aqueous limit of 37 wt%, whilst being thermally and chemically stable under leaching conditions up to 373 K. The proposed leaching process can quantitatively extract Co(II), Mn(II) and Cu(II) from spent cathodes of laptop batteries whilst only extracting 10 % of Ni(II). The latter could be easily recovered as NiCl2·2H2O with 99 % purity through the manipulation of the coordination environment afforded by the DES relative to aqueous media. Key leaching parameters were the HCl:metal molar ratio and temperature, both having a significant impact on the leaching efficiency and its selectivity. Metal recovery was accomplished after stripping of the loaded DES solution via a straightforward sequential precipitation process, with 99 % Co(II) and 98 % Mn(II) being precipitated with 95 % and 81 % purity, respectively. The reported system presents a better atom economy compared to other DES and conventional inorganic acids, providing a new mild approach for the simultaneous leaching and separation of metals from lithium-ion batteries.

CO2-responsive deep eutectic solvents for the enhanced extraction of hesperidin from Fertile orange peel

Hesperidin, also known as vitamin P, is widely studied for its distinctive potential in food and pharmaceutical industries. This work focuses on the research of CO2-responsive deep eutectic solvents (DESs) used as recyclable extractants for efficient extraction of hesperidin from Fertile orange peel. Reversible phase transformation of DES solution was achieved by bubbling CO2/N2. The maximum extraction yield of 22.39 mg/g was obtained for hesperidin under the following conditions: DES-6 (triethanolamine: 4-methoxyphenol = 1:1) used as extractant, water content of 35 wt%, solid–liquid ratio of 1:60 g/mL, extraction temperature of 25 °C, and ultrasonic time of 25 min, which was much higher than that extracted by methanol. Hesperidin of 74.38% was recovered in top phase after CO2 triggering. Density function theory (DFT) results indicated that hydrogen and π-π bonds were the main factors affecting hesperidin extraction. This study provides a new idea for extracting natural bioactive compounds using recyclable extractants.

DBS‐Based Eutectogels: Organized Vessels to Perform the Michael Addition Reaction**

AbstractSupramolecular eutectogels were obtained from the gelation of 1,3 : 2,4‐dibenzylidene‐D‐sorbitol (DBS) in cholinium chloride‐based deep eutectic solvents (DES), differing for the nature of the hydrogen bond donor. Ethylene glycol, diethylene glycol, triethylene glycol, glycerol and urea were tested. Soft materials were fully characterized, determining critical gelation concentration, gel‐sol transition temperatures and mechanical properties. Furthermore, to have information about the organization of the gelator in the tridimensional network, resonance light scattering, circular dichroism and microscopy investigations were performed. Eutectogels were used as organized “vessels” to perform the L‐proline catalyzed Michael addition reaction. The probe reaction was carried out in gel phase and in DES solution. Data collected shed light on the effect that gel microenvironment exerts on the outcome of the reaction. In general, gel phases allowed having comparable or even better results than the ones collected in DES solution, with better results obtained in soft materials with the highest organization, as accounted for by the presence of larger aggregates and the occurrence of stronger intermolecular interactions. In turn, this accounts also for the effect of substrates structure that indicates that better yields could be obtained in the presence of more flexible nucleophile and dienones, having more extended π‐surface.

Unveiling the Influence of Hydrated Deep Eutectic Solvents on the Dynamics of Water-Soluble Proteins.

Deep eutectic solvents (DESs) are mixtures of two or more pure compounds (e.g., Lewis or Brønsted acids and bases, anionic and/or cationic species) in a well-defined stoichiometric proportion, with a melting point lower to that of an ideal liquid mixture. These neoteric solvents are highly tunable through varying the structure or relative ratio of parent components and have been evaluated as solvents able to improve biomolecules' performance, specifically their stability and biocatalytic properties. Inspired by a recent crystallographic study, we have explored through molecular dynamics (MD) simulations the dynamic properties of two different proteins (hen egg-white lysozyme and the human VH antibody fragment HEL4) in a (20% w/w) hydrated solution of choline chloride-glycerol (1:2). We have developed proper force fields to account for DES, protein, and DES-protein interactions, which have been calibrated using pair distribution function measurements of pure DES solutions. MD results show that the presence of DES quenches the protein motion, increasing the rigidity of the overall protein structure. Specific interactions among DES components and protein residues, such as those between choline ions and two Tryptophan residues of lysozyme, may amplify the protein-DES interactions and lead to protein crystallization in the presence of hydrated DES. These findings open new horizons to improve or achieve control on protein properties by a proper choice of hydrated DESs used as solvents.