Sustainable Solvents Research Articles

Tailoring Deep Eutectic Solvents to Provoke Solubility and Bioavailability of Naringin: Implications of a Computational Approach.

Recently, the applications of deep eutectic solvents (DESs) as green and sustainable solvents for the solubilization of functional foods and phytophenols have dramatically risen concerning global issues on the utilization of organic solvents. Nevertheless, developing a suitable DES system for phytocomponents to enhance its solubility and bioavailability is complex and requires a sound experimental setup. Herein, we have attempted to develop DES encompassing the choline chloride (ChCl) along with oxalic acid (OA), l-glutamine (l-Glu), urea (U), and glycerol (Gro) at different ratios to elicit the solubility and bioavailability of naringin (NAR). Several DES systems were designed and tested for solubility, kinematic viscosity, and pH. Among these, DES-NAR encompassing ChCl/Gro in a 1:3 ratio exhibited the maximum solubility of NAR (232.56 ± 7.1 mg/mL) and neutral characteristic and thus considered suitable for NAR. Further, the conductor-like screening model for real solvents (COSMO-RS) has been employed to estimate the molecular and electrostatic interactions. DES-NAR was evaluated by polarized optical microscopy, Fourier-transform infrared (FTIR), differential scanning calorimetry (DSC), and 1H NMR to investigate the molecular transition and interaction. Further, diffusion and permeability studies were performed, which suggest significant improvements in DES-NAR. Likewise, the pharmacokinetic studies revealed a two times increase in the oral bioavailability of NAR in a designed DES system. Thus, the work represents a systematic and efficient development of the DES system for a potential phytocomponent considering the biosafety impact, which may widen the interest in pharmaceutical and food sciences.

Using novel hydrophobic deep eutectic solvents to improve a sustainable carotenoid extraction from orange peels

Carotenoids are a group of pigments that play a significant role in human health due to their antioxidant properties. This emphasises the importance of their extraction using sustainable solvents as alternatives to hazardous solvents. This study aimed to select and optimise the most promising deep eutectic solvent (DES) for a sustainable carotenoid extraction from orange peels by considering parameters such as efficiency, stability, and physicochemical properties. COSMOtherm software was used to screen 68 hydrophobic and hydrophilic DES. The experimental results demonstrated efficient extraction yields when using hydrophobic DES such as Menthol: Camphor (163.5 ± 1.1 mg/100gfw), and the stability of carotenoids in this solvent was 56% for total carotenoids after 60 days at 4 °C. The ultrasound extraction technique was selected for the optimisation process, and the optimal conditions were 60% ultrasound intensity (120 W), a solvent-to-solid ratio of 20 mL, and an extraction time of 20 min with a yield of 653.5 mg/100 gfw. The results presented in this study demonstrate the capacity of novel hydrophobic DES to extract carotenoids and identify this solvent as a good and sustainable alternative to organic solvents. Improved carotenoid extraction combined with non-toxicity, edibility, and enhanced carotenoid stability makes these extracts appealing for use in food product fortification.

Synthesis and characterization of natural deep eutectic solvents as green extractants for isolation of bioactive flavonoids from Amaranthus viridis

The application of principles of Green Chemistry is gaining importance in various fields of research to eliminate the risk of environmental pollution from toxic chemicals. Safer industrial processes reduce the risk of health problems to the consumers as well as result in a sustainable and cleaner environment. This paper indicated the synthesis of sustainable green solvents having greater solvation property to extract phytochemicals from plants in comparison to an organic solvent. Natural deep eutectic solvents (NADES) containing choline chloride (ChCl), 1,2-propanediol (PG) and citric acid (CA) were prepared followed by the study of its physicochemical properties. Selected NADES's were then used for the first time to extract bioactive components from Amaranthus viridis (AV) and compared with the ethanolic extract. The results indicated the total phenolic content (TPC) value of 54.6, 250, 40.6 mgGAE/g, total flavonoid content value (TFC) of 16.5, 82.1, 20.4 mgQUE/g and antioxidant activity of 30.3, 42.9, 22.6 mg/ml of AV extract in ChCl:PG:H2O-1:2:1 (AV-PG), AV extract in ChCl:CA:H2O-1:1:1 (AV-CA) and AV extract in ethanol (AV-E) respectively. A high concentration of bioactive components in NADES extracts was confirmed by phytochemical analysis comparing to ethanol extract. Antibacterial activity of AV-CA extract showed inhibition zone of 30 mm against both gram-positive and gram-negative bacterial strains. From the results it can be concluded that NADES extracts can be used for biomedical applications as an improvement in the drug delivery system by eliminating the toxic solvents.

The quest for a better solvent for the direct hydration of cyclohexene: From molecular screening to process design

Cylcohexanol is an essential bulk chemical that can be produced via cyclohexene hydration, a liquid-liquid two-phase reaction that is limited by the low reaction rate and the equilibrium conversion. Adding an appropriate solvent is the most promising method to break through these limitations. However, in previous works the solvent was almost blindly selected without a global consideration. In this work, a rational multiscale method is proposed for the effective selection of an economical and sustainable solvent for the direct hydration of cyclohexene. At the molecular scale, liquid-liquid phase equilibrium was estimated using group contribution methods to rapidly screen the potential solvent candidates from a range of organics, based on the partition coefficient. At the reactor scale, the candidates were experimentally investigated to pick out the solvents that could significantly improve the conversion, without introducing side reactions or deactivating the catalyst. At the process scale, the total annual cost (TAC), CO2 emission, and other metrics were calculated to evaluate the eco-efficiency of all solvents. Using this multi-scale method, acetophenone was selected as an eco-efficient solvent from over 100 organics, resulting in the reduction of TAC by 8 % and CO2 emission by 17 % in the production process. Using acetophenone also led to the increase of cyclohexanol yield from 12.3 % to 27.6 % without the occurrence of side reactions and catalyst deactivation.

Green and sustainable solvents of the future: Deep eutectic solvents

Deep Eutectic solvents (DESs) can be termed as the New Age Solvents that have emerged as potential alternatives to conventional solvents in many industrial applications. These encompass various types of DES, their synthesis, multifarious industrial applications, and superiority over industrial solvents and Ionic Liquids (ILs). This burgeoning interest in the DES has stemmed from their very specific characteristics of being safe, less hazardous, “green” as compared to ILs, biodegradable, ease of being prepared in commercial proportions, low cost of preparation and several other interesting features. Within a very short span of time, DESs have been employed for a large and diverse range of applications including separation processes, extraction of solvents, pharmaceutical processing, environmental protection, material synthesis etc. This review brings out the recent happenings in the field of DES research, types and synthesis. It also sheds light on commercial applications of DESs as green and sustainable solvents of the future as a feasible alternative to the present day hazardous and carcinogenic industrial solvents. The reusability, regeneration, scalability for industrial applications, promising applications at commercial scale have also been discussed together with theoretical and computational models.

Sustainable solvent metal lift-off for compound semiconductor fabrication with improved manufacturability

Due to concerns regarding substrate damage, wet photoresist removal has been adopted over dry etch techniques for certain metal lift-off processes on substrates and metals that are susceptible to plasma damage. Wet photoresist removal generally requires the use of polar aprotic solvents and historically n-methyl pyrrolidone (NMP) has been broadly adopted. A successful lift-off process requires consideration of both the solvent used to remove the photoresist as well as the correct photoresist retrograde profile. As features become smaller and more critical, the overall photoresist profile becomes more challenging. The use of bottom anti-reflective coatings (BARC) has become necessary to better control the reflected light and minimize potential defectivity during patterning. However, addition of the BARC layer complicates the resist removal process by requiring a secondary cleaning step since wet photoresist strip chemistries, such as NMP, generally do not remove it. There have been several developmental efforts in the metal lift-off industry to formulate a solvent, which could remove both photoresist and BARC, concurrently. In the first half of this paper, various wet photoresist removers are compared to determine the most effective wet resist strip for removal of both photoresist and BARC in one step. The second half of the paper summarizes two different metal liftoff processes and compares the performance of the best chemistry from initial experimentation, Technistrip® MLO-07, to NMP.

Odyssey of Deep Eutectic Solvents as Sustainable Media for Multicomponent Reactions: An Update

Abstract:Deep eutectic solvents (DESs) are frequently defined as binary or ternary mixtures of compounds that are able to associate mainly via hydrogen bonds. As the interest in green sustainable solvent’s spread over the entire scientific community, DESs find applications as alternative solvents and/or catalysts for organic transformations. Advantages such as easy reproducible preparation, low cost, environmentally benign nature, wide liquid range, excellent thermal stability, negligible vapour pressure, recyclability, and tunable properties render DESs as a sustainable candidate of catalyst/solvent for futuristic transformations involving multicomponent strategy. In view of the escalating demand for green synthetic approaches, this paper retrospects the advances made in the application of DES in multicomponent reactions since 2018.

Insights into the Solvation Characteristics of Zwitterionic Deep Eutectic Solvents Using Multiple Polarity Scales

Deep eutectic solvents (DESs) formed by mixing zwitterionic hydrogen bond acceptors (HBAs) with diol- and organic acid-based hydrogen bond donors (HBDs) are popular sustainable solvents. In addition to possessing an amphiphilic character, zwitterionic DESs offer unique solvation properties, unlike those composed of halide-containing HBAs. While all other popular classes of DESs have been investigated, no study has attempted to characterize the solvation characteristics of zwitterionic DESs. In this study, the solvation properties of betaine [Bet]-, sulfobetaine-, and l-carnitine [l-Car]-based DESs were thoroughly investigated for the first time using solvatochromic dye methods and inverse gas chromatography (IGC). The Nile red polarity scale revealed that DESs composed of organic acids were generally more polar than diol-based DESs. Kamlet–Taft solvent parameters revealed that glycerol-based DESs offered exceptionally high hydrogen bond donating ability compared to those composed of 1,4-butane diol and triethylene glycol. The Abraham solvation parameter model revealed hydrogen bond basicity to be the most dominant interaction, and it was generally higher for diol-based HBDs compared to organic acid-based HBDs. Additionally, sulfobetaine HBAs possessing longer alkyl chains generally offered higher dispersive-type interactions and hydrogen bond basicity compared to [Bet] and [l-Car] salts. This is the first study to combine and compare results from solvatochromic dye methods and IGC in an attempt to comprehensively explain and predict the solvation characteristics of zwitterionic DESs.

Green solvents for deoiling pumpkin and sunflower press cakes: impact on composition and technofunctional properties

SummaryThe applicability of protein‐rich press cake from mechanical seed oil production is limited because of its relatively high residual oil content. To overcome this drawback, pumpkin and sunflower press cakes were deoiled at room temperature by using two green solvents, namely ethanol and isopropyl alcohol. Hexane, which is mostly used in the plant oil industry, was used as a reference. The derived meals were analysed regarding composition as well as with respect to technofunctional properties such as water‐binding capacity, water solubility, nitrogen solubility and colour. Extraction efficiencies of more than 94% were achieved once the solvents were refreshed during extraction. In contrast to pumpkin meal, solvent‐specific differences in the residual oil content of sunflower press cake were discovered, which was lowest for hexane and highest for ethanol. The water‐binding capacity and nitrogen solubility of the meals were improved after solvent extraction. The results indicate that it is possible to replace hexane with more sustainable green solvents such as ethanol or isopropyl alcohol to extract residual oil from sunflower and pumpkin press cake.

Unexpectedly Superhigh Toxicity of Superbase-Derived Deep Eutectic Solvents albeit High Efficiency for CO2 Capture and Conversion

Superbase-derived deep eutectic solvents (DESs) are considered as biodegradable, low toxic, and sustainable solvents for efficient capture and conversion of carbon dioxide. However, do superbase-derived DESs have low toxicity just as reported? Herein, contradictory to the conventional thought, we find that the toxicity of superbase-derived DESs is super high. The toxicity of superbase-derived DESs in this work could be ca. 266 times that of DESs previously reported. Moreover, toxicity could be tuned by changing hydrogen bond donors, hydrogen bond acceptors, and mole ratios. The results indicate that the types of hydrogen bond donors had a paramount effect on the toxicity of DESs, and increasing the molar ratio of higher toxic components will also increase the toxicity of DESs. This work will provide possible ways to reduce the toxicity of DESs for achieving sustainable and green capture and conversion of carbon dioxide.

Stepwise Growth of Copper-Based Coordination Polymer on α-MnO2 Nanorods for Sustainable Reduction of Nitroarenes

Metal oxide/coordination polymer composites have gained great attraction due to their synergistic effects to increase their efficiency in various fields. In this work, a Cu-based coordination polymer (Cu-CP) was grown on the surface of α-MnO2 nanorods via stepwise assembly of benzene-1,4-dicarboxylic acid (H2BDC) as a ligand and a Cu(II) ion as a metal center. Comprehensive characterization techniques confirmed the successful growth of Cu-CP on the surface of α-MnO2 without affecting the morphology of pristine α-MnO2 nanorods. The obtained nanocomposite (α-MnO2/Cu-CP) revealed outstanding activity in the catalytic reduction of nitroarenes to aminoarenes under mild reaction conditions and afforded wide substrate applicability (more than 99% for nitrobenzene and 70–99% for other substituted nitroarenes during 1 h at room temperature). Importantly, α-MnO2/Cu-CP served as a better catalyst than bare α-MnO2 and Cu-CP due to the synergistic effects between building components. In addition, α-MnO2/Cu-CP was easily separable by centrifugation and its catalytic activity remained unaffected over five cycles. The use of water as a sustainable and green solvent and non-toxic and inexpensive metals used for the synthesis of the catalyst along with easy recovery and stability of the catalyst make the present protocol economical and sustainable. The time-dependent reduction kinetics followed pseudo-first-order kinetics with respect to the substrates.

In situ Formation of Polymer Microparticles in Bacterial Nanocellulose Using Alternative and Sustainable Solvents to Incorporate Lipophilic Drugs

Bacterial nanocellulose has been widely investigated in drug delivery, but the incorporation of lipophilic drugs and controlling release kinetics still remain a challenge. The inclusion of polymer particles to encapsulate drugs could address both problems but is reported sparely. In the present study, a formulation approach based on in situ precipitation of poly(lactic-co-glycolic acid) within bacterial nanocellulose was developed using and comparing the conventional solvent N-methyl-2-pyrrolidone and the alternative solvents poly(ethylene glycol), CyreneTM and ethyl lactate. Using the best-performing solvents N-methyl-2-pyrrolidone and ethyl lactate, their fast diffusion during phase inversion led to the formation of homogenously distributed polymer microparticles with average diameters between 2.0 and 6.6 µm within the cellulose matrix. Despite polymer inclusion, the water absorption value of the material still remained at ~50% of the original value and the material was able to release 32 g/100 cm2 of the bound water. Mechanical characteristics were not impaired compared to the native material. The process was suitable for encapsulating the highly lipophilic drugs cannabidiol and 3-O-acetyl-11-keto-β-boswellic acid and enabled their sustained release with zero order kinetics over up to 10 days. Conclusively, controlled drug release for highly lipophilic compounds within bacterial nanocellulose could be achieved using sustainable solvents for preparation.

Introduce dimethyl ether (DME) as a solvent for steam-assisted gravity drainage (SAGD) co-injection: An effective and environmental application

Conventional heavy oil and bitumen thermal recovery is currently facing increasing energy demands and climate-related challenges. Dimethyl ether (DME) as a renewable and sustainable solvent was recently proposed as a possible solution for a carbon transition to hydrogen economics. However, only limited studies with unclear mass transfer mechanisms have been conducted on DME and its co-injected on steam-assisted gravity drainage (SAGD) optimization. In this study, a numerical model was developed to investigate the DME-based expanding-solvent SAGD (ES-SAGD) process to capture the complex mechanisms involved. The impact of temperature on relative permeability curves and coupled heat/mass transfer were further discussed in detail. The results of DME-based ES-SAGD and conventional SAGD were compared in terms of process performance and energy efficiency as well as carbon intensity. The optimal range of DME concentration was investigated to achieve the highest recovery factor, and with the assistance of DME carbon intensity can be reduced to one quarter to half of that in conventional SAGD. The study confirmed DME is a novel solvent that leads to the viable performance of ES-SAGD to meet carbon emission reduction objectives.

Hybrid valorization of biodiesel production using sustainable mixed alcohol solvent

Hybrid valorization of biodiesel production using sustainable mixed alcohol solvent

Butylene Glycol Used as a Sustainable Solvent for Extracting Bioactive Compounds from Camellia sinensis Flowers with Ultrasound-Assisted Extraction.

The research aims to assess the yield of bioactive compounds and their antioxidant activities obtained from tea flowers using an ultrasound-assisted extraction method with butylene glycol (BG-UAE) through Box-Behnken design. It investigates the bioactive compounds including the total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC) and analyzes their antioxidant activities, bioactive compound composition by liquid chromatography triple quadrupole tandem mass spectrometry, and their cellular activities via UAE and maceration using BG or ethanol as the solvent. Under optimal conditions, the values of the TPC, TFC, TTC, 1,1-diphenyl-2-picrylhydrazil radical scavenging assay, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid radical scavenging assay, and ferric reducing antioxidant power assay (FRAP) of the BG-UAE extract were 54.00 ± 1.19 mg GAE/g sample, 291.47 ± 3.34 mg QE/g sample, 65.37 ± 1.78 mg TAE/g sample, 106.45 ± 1.21 mg TEAC/g sample, 163.58 ± 2.76 mg TEAC/g sample, and 121.31 ± 4.75 mg FeSO4/g sample, respectively. Except for FRAP, BG-UAE exhibited the highest values in all parameters compared to the other extraction methods. Catechins and caffeine were predominantly detected in tea flower extracts through UAE with BG and ethanol (EtOH-UAE). BG-UAE exhibited greater cell viability and cellular antioxidant activity than EtOH-UAE. The researcher expects that this research will contribute to the emergence of a green extraction technique that will offer larger functional components with economic and environmental benefits and minimal chemicals and energy use.

Enhanced Recovery of Natural Antioxidants from Grape Waste Using Natural Eutectic Solvents-Based Microwave-Assisted Extraction.

The evaluation of sustainable solvents as alternatives to more harmful conventional solvents combined with intensification techniques to recover phenolic compounds from agri-food waste is in the spotlight. The wine industry generates large amounts of waste as a consequence of grape processing operations, which can be revalued by solvent extraction of valuable antioxidants for food and fine chemical applications. Therefore, the present study focuses on the use of natural eutectic solvents (NAESs) with benign environmental, health, and safety profiles, for valorization of grape waste in the context of a circular economy. Herein, up to 15 NAESs consisting of combinations of three hydrogen bond acceptors (choline chloride, L-proline, and betaine) and four hydrogen bond donors (1,2-propanediol, glycerol, and 1,2- and 1,3-butanediol) were evaluated for antioxidant recovery. After an initial screening of the performance of NAESs by conventional extraction, the process was intensified by microwave-assisted extraction (MAE). The extracts were analyzed by UV/VIS spectrophotometric and HPLC methods. Promising results were obtained with the solvent betaine, 1,2-butanediol [1:4], using MAE at 100 °C for 3 min. Overall, the proposed NAESs-based MAE method was successfully applied to recover target compounds from grape waste, with great prospects for the antioxidants market and sustainable development for the winery sector.

Towards a More Sustainable Photocatalyzed α‐Arylation of Amines: Green Solvents, Catalyst Recycling and Low Loading

AbstractA more sustainable and efficient protocol for the photocatalytic α‐amino arylation promoted byfac‐Ir(ppy)3was developed. Three noteworthy results were achieved: i) the replacement of toxic medium DMA with the greener solvents NBP and NHP, and the concurrent improvement of the process efficiency by lowering both the amine and the base amount; ii) the development of a recycling protocol for both the sustainable solvent NHP and the commercially available costly photocatalystfac‐Ir(ppy)3, achieving environmental and economic benefits. This approach to the photocatalyst recovery avoids very demanding catalyst structural modifications; iii) the protocol in green solvents proved to be scalable up to 10 mmol of limiting reagent, maintaining excellent performance also lowering the photocatalyst loading down to 0.05 mol%. This is the first example of photocatalytic α‐arylation of amines promoted by such a low amount of catalyst. Lastly, the versatility of this approach was demonstrated by extending the use of the green solvent NBP to another photoredox process.magnified image

Natural deep eutectic solvents as a green extraction of polyphenols from spent coffee ground with enhanced bioactivities.

Conventional extraction techniques are usually based on highly pollutant and/or flammable organic solvents. Therefore, alternative environmentally friendly extraction methods are of particular interest for the recovery of bioactive compounds for their application as food ingredients and/or nutraceuticals. Natural deep eutectic solvents (NADES) are a green and nontoxic attractive alternative to hydroalcoholic extraction. NADES media primarily depends on the intermolecular interactions (hydrogen bonding) among their components to form a eutectic mixture with a much lower final melting point than its individual components. Examples of natural deep eutectic NADES solvents include aqueous solutions (25%-50% water) of choline chloride, sugars, and polyols. This study aimed to investigate the application of two NADES, namely, betaine:triethylene glycol (Bet : TEG) and choline chloride:1,2-propanediol (Chol : Prop), as sustainable green solvents for the extraction of polyphenols from spent coffee ground (SCG), a by-product of coffee processing. In particular, the extraction yield and selectivity were evaluated and compared with conventional green extractions (hot water and a hydroalcoholic solution). In addition, the effect of NADES on the antioxidant and antimicrobial activity of the extracts was investigated. The main outcomes were as follows: (i) NADES were as effective as other conventional green solvents in the extraction of polyphenols with the added advantage of operating at milder temperature conditions, without flammable solvents and with sustainable and natural compounds; (ii) the antimicrobial activity of the NADES extracts was 10 times higher than that of the ethanolic and aqueous extracts. Given the low toxicity of NADES, they could be used as formulation aid for food ingredients.

Experimental study on CO2 separation using hydrophobic deep eutectic solvent based supported liquid membranes

Deep eutectic solvents (DESs) have been proposed as a viable and more sustainable solvent for CO2 capture, owing to their low volatility and tunable properties. In this work, polymer membranes were combined with hydrophobic DESs to prepare supported liquid membranes (DES-SLMs), and the potential of using SLMs for CO2/N2 separation was investigated. COSMO-RS model simulations, bond energy analysis as well as stability tests were used to select the polymeric porous support. Hydrophobic polyvinylidene fluoride (PVDF) with a nominal pore size of 0.1 μm was chosen to support three selected hydrophobic DESs. The gas permeabilities through three selected DES-SLMs were experimentally determined, where the thymol-coumarin (1:1) based SLM showed the best performance with a CO2 permeability of 175.0 Barrer and selectivity of 30.2 at room temperature. The separation capability was further improved by mixing the DES with traditional physical absorbents. In addition, the effects of water presence in the gas phase on the DES-SLM were investigated. The membrane was physically stable, but the ideal selectivity of CO2/N2 through the membrane deteriorated with time on steam. By predicting the permeabilities of CO2 and N2 through traditional organic liquid based SLMs, the prospects of developing DESs for SLM applications were demonstrated. Finally, an advanced membrane capture process for a natural gas-fired combined cycle (NGCC) power plant was studied with process simulation and economic analysis, where the SLMs are used to purify the CO2 product.

Copper-mediated synthesis of temperature-responsive poly(N-acryloyl glycinamide) polymers: a step towards greener and simple polymerisation.

Stimuli-responsive materials with reversible supramolecular networks controlled by a change in temperature are of interest in medicine, biomedicine and analytical chemistry. For these materials to become more impactful, the development of greener synthetic practices with more sustainable solvents, lower energy consumption and a reduction in metallic catalysts is needed. In this work, we investigate the polymerisation of N-acryloyl glycinamide monomer by single-electron transfer reversible-deactivation radical polymerisation and its effect on the cloud point of the resulting PNAGA polymers. We accomplished 80% conversion within 5 min in water media using a copper wire catalyst. The material exhibited a sharp upper critical solution temperature (UCST) phase transition (10-80% transition within 6 K). These results indicate that UCST-exhibiting PNAGA can be synthesized at ambient temperatures and under non-inert conditions, eliminating the cost- and energy-consuming deoxygenation step. The choice of copper wire as the catalyst allows the possibility of catalyst recycling. Furthermore, we show that the reaction is feasible in a simple vial which would facilitate upscaling.