Green Solvent Research Articles

HIGH-ADDED VALUE PRODUCTS FROM DISCARDED COOKING OIL

Vegetable oils are widely used in human consumption as food, with increasing productivity. As they are sustainable raw materials, they are suitable substitutes for fossil-derived raw materials and have great potential for producing high-value bioproducts, contributing to sustainability, the economy, and environmental issues. This article explores multiple applications of vegetable oils, highlighting residual oil included in making soaps, biofuels, animal feed, green solvents, bioasphalt, and asphalt binders. It also addresses the treatment of these vegetable oils with enzymes and the methods for converting soybean oil into biofuels, highlighting their properties that favor efficiency and the reduction of pollutant gas emissions. In addition, the extraction and purification processes that make obtaining ingredients with more excellent market value possible are discussed.

Mixed Carboxylate Ligands Bridging Tetra-Pr3+-Encapsulated Antimonotungstate: Syntheses, Structure, and Catalytic Activity for Imidazoles Synthesis.

Multinuclear Pr-containing antimonotungstate [Pr4(H2O)10W6O13(mal)2(OAc)(B-α-SbW9O33)4]21- (Pr-1, mal = malate anion, OAc = acetate anion), bridged by organic carboxylic acid, was synthesized through a one-pot assembly reaction and structurally characterized. Pr-1 is composed of four [B-α-SbW9O33]9- fragments fused together by an organic-inorganic hybrid central [Pr4(H2O)10W6O13(mal)2(OAc)]15+ cluster core through 24 μ2-O atoms. Notably, the central cluster comprises unprecedented decanuclear Pr4(H2O)10W6O13 jointly decorated by two types of carboxylic acid ligands. This integration of rare earth-containing antimonotungstate with mixed organic carboxylate ligands is very rare in POMs chemistry. Pr-1 exhibits excellent catalytic activity in the cyclo-condensation reaction involving benzil, aldehyde, and NH4OAc. A series of 2,4,5-trisubstituted imidazoles were synthesized in remarkable yields using iPrOH as a green solvent.

A Novel Delayed Phase Inversion Strategy Enables Green PVDF Membranes for Membrane Distillation

Polyvinylidene fluoride (PVDF) membranes are extensively utilized in membrane distillation (MD) for water treatment. However, traditional methods easily form asymmetrical membranes with dense skin layers that are detrimental to membrane flux. Herein, an eco-friendly PVDF membrane was fabricated by utilizing a delayed phase separation process without using any pore-forming agents. In addition, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (PolarClean) was used as a green solvent without posing risks to humans and the environment. It was demonstrated that the PVDF concentration is crucial in influencing the microstructures and performance of the resulting membranes. As the PVDF concentration increased, the morphology changed significantly, resulting in a reduction of pore size. When feeding the device with NaCl solution at a concentration of 35 g/L, the MD water vapor flux reached 18.49 kg·m⁻2·h⁻1, while maintaining a salt rejection of over 99.97% during the continuous operation for 24 h. This work presented a method for producing green PVDF membranes via delayed phase inversion with satisfactory water vapor flux and salt rejection, highlighting their prospect for effective applications in MD for water treatment.

Molecular dynamics simulation of extraction of Curcuma longa L. extract using subcritical water.

Humans have utilized plants for various purposes, including sustenance and medical treatment for millennia. Researchers have extensively investigated medicinal plants' potential in drug development, spurred by their rich array of chemical compounds. Curcumin, a valuable bioactive compound, is extracted from Turmeric, known by the scientific name Curcuma Longa L. Notably, curcumin boasts potent antioxidant and anti-inflammatory properties, making it a promising candidate for treating cancer and other microbial diseases. Therefore, the simulation study of the extraction of this important medicinal compound by water, which is a green solvent, was carried out. This study employed molecular dynamics simulation for the first time to explore the extraction of Curcuma Longa L. extract using subcritical water. The simulations were carried out at constant pressure and different temperatures, using the Compass force field in the Lammps simulation package. The findings revealed an increase in the amount of Curcuma longa extract with rising temperature, indicating a weakening of hydrogen bonds in water molecules. Water lost its polar state with increasing temperature and became a suitable non-polar solvent for extracting non-polar compounds. The average absolute relative deviation (AARD) for calculated and simulated density data was 6.45%.

Physicochemical and Antimicrobial Properties of Lactic Acid-Based Natural Deep Eutectic Solvents as a Function of Water Content

The interest in natural deep eutectic solvents (NADESs) in green technology as an alternative to organic solvents has grown over the past decades. In this work, for the first time, the effect of dilution with water on the physicochemical and antimicrobial properties of lactic acid-based NADES with choline chloride (NADES1), sorbitol (NADES2), and glucose (NADES3) was systematically studied. According to FTIR data, after the dilution of NADESs with water, the strong hydrogen bonds weakened, however, were not destroyed after dilution of up to 40% water. The dilution of NADES with water resulted in a linear decrease in density and refractive index and in a linear increase in pH. The equations for the prediction of NADES density, pH, and refractive index as a function of water content were calculated. The viscosity decreased by half after adding approximately 10% water. The initial viscosity of NADES2 and NADES3 was significantly different. However, after adding 20% of the water, the viscosity was almost the same. The most pronounced decrease in surface tension (by 46.7%) was found for NADES1. The water activity was decreased in the following order: NADES3 > NADES1 > NADES2. The dilution of NADES with water caused a gradual increase in water activity. NADES1 showed the lowest minimal inhibitory concentrations (MIC) (7.8, 3.9, and 0.98 mg/mL) and minimum bactericidal concentrations (MBC) (15.6, 7.8, and 1.95 mg/mL) for Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. The antimicrobial activity was decreased by 2–8 times after the addition of 40% water. The water activity for all tested NADES together with low pH could explain the antimicrobial effect. The revealed regularity can be useful for the prediction of NADES properties and for the selection of green solvents on a laboratory and industrial scale.

Structural characterization and physicochemical properties of different hydrophilic natural deep eutectic solvents.

To overcome the toxic nature of organic solvents, scientific interest in the use of green solvents, particularly natural deep eutectic solvents (NADES), has increased over the past decade, leading to new applications in the food, nutraceutical, pharmaceutical, and cosmetic industries. Understanding the physicochemical properties and molecular interactions of NADES is essential for uncovering new potential applications in these fields. In this study, several lactic and citric acid-based NADES, as well as chloride choline- and urea-based NADES, were evaluated for their physicochemical properties, including density, pH, viscosity, conductivity, and refractive index. Additionally, nuclear magnetic resonance (NMR), and in particular nuclear Overhauser enhancement spectroscopy (NOESY), was employed to investigate the intermolecular interactions between the NADES components to confirm the formation of the eutectic mixture. The extraction efficiency of the confirmed NADES was tested for extracting polyphenols as a proof of concept to highlight their relationship with the measured properties. Lactic and choline chloride-based NADES provided the highest extraction yields. These results were also compared with the predicted extraction capabilities of each NADES provided by the COSMO-RS software.

A Validated Trigonelline-Based Method for the Standardization and Quality Control of Trigonella foenum-graecum L.

Background Fenugreek, or Trigonella foenum-graecum L, is an edible and medicinal plant of the Fabaceae family. Fenugreek seeds contain a variety of phytochemicals, including proteins, lipids, amino acids, vitamins, flavonoids, steroidal saponins, coumarin, and alkaloids. Trigonelline TG is a bioactive plant alkaloid initially extracted from fenugreek seeds. A substantial portion of fenugreek’s health benefits may rely on the presence of TG. This study addresses the research gap for a fast, green, and economical method for quantifying trigonelline (TG) in fenugreek. Methods Fenugreek seeds from various origins were extracted using three green solvents: acetone (ACt), ethanol (EtOH), and water (H2O). The UPLCMSMS method was developed and validated using a green mobile phase of H2O: EtOH, and an r2-value of 0.999 in the linearity range of 0.1-500 ppb was adopted. The method was validated with an accuracy of 98.6% for trace analysis of TG using a small amount (10 mg) of fenugreek samples from five different origins. Results The average extract yield (±SD) was 5.36±6.3, with the highest extract yield observed in H2O. The ESI (+ve) of the UPLCMSMS resulted in the fragmentation pattern (m/z) 138→94.10→92.05→78.20. The TG quantification revealed an average TG concentration of 181.4, with the highest amount of TG in H2O extract (392.7±132.4 ppb), followed by EtOH (91.9±83.3 ppb) and ACt (59.5±30.9 ppb). The TG amount observed in the validation step substantiated the efficiency and reproducibility of the developed method. Conclusions The method may be used as an effective tool for a green, rapid, economical, and eco-friendly extraction and quantification of TG in diverse matrices of pharmaceutical, cosmeceutical, herbal, and food products.

Multicomponent Cyanation of 2‐Amino‐3‐cyano‐4H‐chromenes in Aqueous Media

AbstractChromenes represent a pivotal molecular structure found in a diverse range of biologically active compounds. Specifically, derivatives of 2‐amino‐3‐cyano‐4H‐chromene have demonstrated pharmacological applications, displaying potential antioxidant and anticancer activities. This has heightened interest in the exploration of new and more efficient methods for their synthesis. In recent years, few examples have emerged, focusing on the organocatalytic and enantioselective synthesis of 2‐amino‐3‐cyano‐4H‐chromene derivatives, although the overall number of works to date is limited. In this study, we present the results of the synthesis of 2‐amino‐4H‐chromen‐3,4‐dicarbonitriles through a Michael addition of cyanide to 2‐iminochromenes. To achieve this, we utilized a mild source of cyanide (acetone cyanohydrin), green solvents and catalytic conditions at room temperature, via a multicomponent approach. Furthermore, we initiated the enantioselective study of this process using chiral organocatalysts obtaining promising preliminary results.

Fast Dissolution of Chitin in Amino Acids Based Deep Eutectic Solvents Under the Assistance of Microwave.

Due to the abundant hydrogen bond networks, high crystallinity, and high molecular weight of chitin, it is difficult to dissolve chitin in most solvents. Meanwhile, most of the existing solvent systems have the disadvantages of high toxicity, low solubility, and high cost. Therefore, the efficient and rapid dissolution of chitin using green solvents is urgently needed. In this work, ternary DES with amino acids, urea, and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) is prepared at first. Then chitin can be dissolved fastly with the assistance of a microwave. Compared with the conventional heating process (110°C, 6-8h), the microwave process can be shortened to only 3-10min. The successful dissolution of chitin is verified by means of fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), rheology studies, and optical light microscope, and the dissolution mechanism contributed to the synergistic destroying of the hydrogen bond networks of chitin by amino acids and DBU. The DES solvent can be well recovered with the remaining of its dissolving ability to chitin.

Analytical Quality by Design Assisted Ecofriendly RP-HPLC Method for the Simultaneous Estimation of Artificial Sweeteners in Commercial Food Samples Utilizing Green Ultrasound Assisted Extraction Technique: Greenness, Blueness and Whiteness Appraisal.

Acesulfame K (E950) and Saccharin Na (E954) are commonly utilized synthetic sweeteners that are added to various processed food products to improve the sweet flavor. It is essential to give priority to environmentally friendly technology while assessing them, as overuse of these sweeteners presents serious health hazards. The main aim of this study was to develop an AQbD aided ecofriendly RP-HPLC technique that can detect both Acesulfame K and Saccharin Na simultaneously incorporating green analytical chemistry (GAC) principles and white analytical chemistry (WAC); using ultrasound-assisted extraction (UAE) technique on commercial food samples. The usage of ethanol was in accordance with eco-friendly ideals due to its ease of use, speed, and lack of environmental impact. Rotatable central composite designs (rCCD) was used for method optimization and a mobile phase consisting of a 50:50 (v/v) mixture of ethanol and 1% aqueous acetic acid (v/v), the separation was carried out on a Zorbax column (SB-C18, 150 × 4.6 mm, 5 µm) with a flow rate of 1 ml/min and a detection wavelength of 217 nm. Acesulfame K had retention duration of 1.134 minutes and Saccharin Na of 2.134 minutes. Acesulfame K and Saccharin Na recovery rates varied among different commercially available food samples, ranging from 65-102% and 75-101%, respectively. At the defined operating point, the developed procedure displays conformity with the previously defined requirements for linearity, accuracy, sensitivity, and repeatability. The most accurate assessments of greenness were produced by the GAPI, AES, and AGREE tools. Results from the Red-Green-Blue 12 (RGB 12) algorithm for whiteness and BAGI for blueness indicate that the method is very practical, cost-effective, and environmentally friendly. The results of this study could pave the way for more eco-friendly and effective AQbD methods to be used in the future for evaluating various sweeteners using green solvents.

Recycling Solid Electrolytes from All-Solid-State Lithium-Ion Batteries by Using Deep Eutectic Solvents as Green Extractants.

All-solid-state lithium-ion batteries (ASSLIBs) are attracting significant attention due to their high energy density, conductivity and safety. However, they are expected to generate substantial waste in the near future, leading to resource depletion and environmental pollution. Therefore, it is crucial to achieve green, mild and safe recovery of ASSLIBs. Here, we for the first time to use green deep eutectic solvents (DESs) to effectively recover solid-state electrolytes (SSEs) fromASSLIBs at mild temperature. Results show that Li leaching efficiency can reach up to 87.5% with a superhigh Li/La selectivity of 1902 at a low temperature of 80 oC. Furthermore, 70 anti-solvents are screened to recycle the dissolved SSEs from leachate and 12 anti-solvents could precipitate SSEs from leachate at room temperature. This research opens new possibilities for recovering SSEs from ASSLIBs using the sustainable, cost-effective and safe solvents.

Extraction and Counter-Current Separation of Phenylpropanoid Glycosides from Pedicularis oederi Vahl by Deep Eutectic Solvent

Deep eutectic solvents (DESs) are mixtures of organic compounds displaying excellent solvent properties while keeping an ecofriendly character. In this study, DESs have been applied to the extraction of phenylpropanoid glycosides from Pedicularis oederi Vahl, successively separated by means of counter-current chromatography. Firstly, the ultrasonic-assisted extraction conditions were optimized by response surface methodology, and the results showed phenylpropanoid glycosides could be well extracted under the optimized extraction conditions with deep eutectic solvents. Then, the sample was separated by counter-current chromatography using ethyl acetate/aqueous solution of choline chloride and glycerol (6:6, v/v) as the solvent system. In about 360 min, four phenylpropanoid glycosides, including 31.6 mg of echinacoside, 65.3 mg of Jionoside A1, 28.9 mg of Forsythoside B, 74.1 mg of verbascoside, and 21.2 mg of kaempferol-3-O-rutinoside were obtained from about 900 mg of the sample. It revealed deep eutectic solvents could be well employed as a green solvent for the extraction and counter-current separation of natural products.

Green liquid supra molecular solvent (SUPRA) phase for fast and selective liquid-liquid micro-extraction of Co2+ ions from aqueous samples

The limitation of Liquid-liquid micro-extraction (LLME) procedures can be the need for the use of a dispersive solvent which should be soluble in both of aqueous and organic phases. In this research, a new method named SUPRA-based LLME, is introduced which uses supra molecular solvent (SUPRA), as an environmentally friendly solvent, for quantitative and selective extraction of Co2+ ions from its aqueous solution via liquid-liquid micro-extraction process. The aqueous immiscible SUPRA phase, composed of vesicles of decanoic acid was synthesized via ex-situ procedure and used as a single liquid phase. In order to make the SUPRA phase selective, N, Nʹ-disalicylidene-3, 4-diaminotoluene (H2dst) was synthesized and completely dissolved in the SUPRA phase. Then the lipophilic and selective prepared liquid sorbent, as liquid SUPRA phase, was used for the facile and selective LLME of Cobalt (II) ions from aqueous samples. Experimental studies showed that there was not any need of dispersing solvent and so liquid SUPRA phase could easily dispersed in the aqueous phase and then separated by centrifugation as the supernatant phase. Then the effects of some important variables on the extraction efficiency were also investigated and optimized. The results showed that under optimal conditions, efficient extraction of Cobalt (II) ions was achieved, about 99 % ± 2.7 (n = 10), in a short time of extraction (10 min), and the linear range of calibration curve was from 500 to 2500 μg L−1 of Cobalt(II) with correlation coefficient of 0.999. Also detection limit and pre-concentration factor were 150 μg L−1 and 35.2, respectively. Although the experimental conditions were optimized for extraction of only Co2+ ions, the selectivity study showed a high tendency of selective liquid SUPRA phase toward extraction of both of Co2+ and Ni2+ ions. The matrix effects on the SUPRA-based LLME of Co2+ ions from matrix samples, factory wastewater and sea-water, were studied and least matrix effects were observed.

Ru(II)‐Catalyzed C8 Alkenylation of Isoquinolones with Allyl Alcohol

AbstractA simple Ru(II)‐catalyzed protocol for the alkenylation of isoquinolones with readily accessible allyl alcohols to generate aldehyde bearing isoquinolones has been developed. The use of green solvent like dimethyl carbonate makes this method environment‐friendly. Experimental studies were carried out to support the proposed mechanism. The reaction was scaled up to showcase the application of the current method.

Green Synthesis of 2-Mercapto 5,6-Dihydro-4H-1,3-Thiazines via Sequential C–S Couplings

The six-membered N,S-heterocyclic 1,3-thiazines and their derivatives are widely acknowledged as pharmaceutical molecules with a wide range of biological activities. In this study, we developed a unique thiol-involved cascade reaction that enables the efficient construction of the 5,6-dihydro-4H-1,3-thiazine scaffold through consecutive intermolecular thiol-isothiocyanate and intramolecular thiol-halogen click reactions. Structurally diverse 2-mercapto dihydrothiazines including three antitumour candidates of bis-dihydrothiazines were readily obtained in high yields from the readily available thiols and 3-chloroisothiocyanate in the green solvent EtOH/H2O (1:1) using K2CO3 (0.6 equiv.) as the base. Between the two synthesis procedures investigated, the microwave-assisted reaction generally behaved more efficiently than that under routine heating conditions. Furthermore, DFT calculation confirmed the sequential addition–substitution mechanism. This cascade C–S coupling reaction methodology offers several advantages, including rapid completion, high reliability, easy purification, and benign conditions.

Effect of modifiers on the stability of 1‑butyl‑3-methylimidazolium-based ionic liquids

The distinctive capabilities of 1‑butyl‑3-methylimidazolium (bmim) cation-based ionic liquids (ILs) to dissolve lignocellulosic biomass offer the potential for the development of novel green bioprocessing technologies based on their utilization as green solvents. The limited range of thermal stability of ILs necessitates the use of various co-solvents to maintain solubility. In the present study, an original approach to determine the degree of degradation of alkylimidazolium ILs was proposed, based on the application of gravimetric analysis method to determine the content of volatile degradation products and high-performance liquid chromatography-high-resolution mass spectrometry (HPLCHRMS) to determine the total degree of degradation. The proposed approach, as well as the combination of HPLCHRMS with gas chromatography-mass spectrometry (GC–MS), was employed to comprehensively characterize the impact of additives and impurities (water, dimethyl sulfoxide, hydrochloric and acetic acids, diethylamine) on the degradation of bmim acetate, chloride, and methyl sulfate during thermal treatment under typical biomass dissolution conditions (150 °C, 24 h). The presence of additives or impurities in the composition of ILs has been found to predominantly contribute to a decrease in the number of volatile compounds formed, while increasing the variety and relative content of non-volatile degradation products. The use of protic solvents and acids results in a decrease in the overall degree of degradation of ionic liquids and in the fraction of volatile compounds formed. This allows for the classification of binary mixtures based on these additives as "green" solvents at temperatures below 150 °C.

Rapid preparation and mechanism investigation of covalent organic framework membranes by 3D printing based on electrostatic spraying

Covalent organic framework (COF) has great advantages in the field of membrane separation, but the efficient and convenient preparation of COF membranes is still a challenge. Herein, we propose a novel method with green solvent for the preparation of COF membranes based on electrostatic spraying, which can be successfully prepared within 10 min, forming the TpPa COF with a pore size of 1.8 nm. Molecular dynamics simulations demonstrate that electrostatic spraying enhances the reaction rate by lowering the energy barrier and increasing the movement of reacting monomers. Atomization of the solvent in electrostatic spraying causes the rapid volatilization of the solvent, resulting in supersaturation of the generated TpPa, precipitation and crystallization, and promotes the formation of TpPa COF structure. The optimal COF membrane for the separation of Congo red wastewater is prepared by adjusting the voltage, concentration, and spraying time, with selectivity of Na2SO4 for Congo Red attaining 118 and water permeance reaching 70.2 L m-2 h-1 bar-1. This work not only elaborates the membrane preparation mechanism in the electrostatic spraying process, but also greatly shortens the time of COF membrane preparation compared to the traditional method (2–3 days), which contributes to the possibility for practical application of COF membranes.

Microwave-Assisted Enzymatic Green Solvent Technology for the Extraction and Characterization of Sesame Seed Oil

Traditional methods of extracting oil with organic solvents raise issues related to health, safety, and the environment. Microwave-assisted enzymatic green solvent extraction (MAEGSE) technology is environment friendly because it involves less hazardous chemical synthesis, utilizes renewable feedstock, and decreases the chemical load and emissions produced by organic solvents. The solvents methanol, ethanol, and various cell wall degrading enzymes such as hemicellulose, viscozyme L, pectinase, xylanase, and cellulase were used in this study. The MAEGSE process of sesame oil was conducted, and the results indicated that, unlike the controlled group, no enzymes were used during the process. Among all the combinations a higher oil extraction efficiency was obtained with combination of pectinase and ethanol (37.27%) followed by the xylanase with ethanol (36.75%) from sesame seed without compromising the quality of oil. Among the enzymes tested, pectinase resulted in the highest oil extraction efficiency, followed by xylanase. Use of pectinase improved the oil extraction efficiency in both ethanol and methanol mediums. The outcomes suggested that the application of pectinase enzymes plays a significant role in increasing the oil yield in comparison with the control without compromising quality of oil. Oil extracted without the use of enzyme (control) had a lower free fatty acid (FFA) concentration than the oils extracted with MAEGSE. Even though the specific gravity (SG) and refractive index (RI) of extracted oils were not significantly different in the solvents, the saponification value (SV), peroxide value (PV), iodine value (IV), and free fatty acid (FFA) were found to have minor differences among the extraction techniques.

In-situ understanding on the formation of fibrillar morphology in green solvent processed all-polymer solar cells

Abstract Solid additive engineering has been intensively explored on morphology tuning for highly efficient all-polymer solar cells (all-PSCs), a promising photovoltaic technology towards multi-scenario application. Although the nano-fibrillar network of the active layer induced by additive treatment is confirmed as the key factor for power conversion efficiency (PCE) of all-PSCs, its formation mechanism is not clearly revealed, for lack of precise and convincing real-time observation of crystallization and phase separation during the liquid-to-solid transition process of spin-coating. Herein we report an in-situ grazing incidence wide-angle/small-angle X-ray scattering (GIWAXS/GISAXS) screening that reveals the fact that naphthalene derived solid additives can suppress the aggregation of the polymer acceptor (PY-IT) at the beginning stage of spin coating, which provides sufficient time and space for the polymer donor (PM6) to form the fibril structure. Moreover, guided by this knowledge, a ternary all-polymer system is proposed, which achieves cutting-edge level PCEs for both small-area (0.04 cm2) (also decent operational stability) and large-area (1 cm2) devices.

Correction to “Investigation of molecular interaction, performance of green solvent in esterification of ethanol and acetic acid at 298.15 K and at 1 atm”

Correction to “Investigation of molecular interaction, performance of green solvent in esterification of ethanol and acetic acid at 298.15 K and at 1 atm”