Current Research in Green and Sustainable Chemistry最新文献

A direct synthesis of trimellitic anhydride (TMA) and hemimellitic anhydride (HMA) has been reported in which all the carbons of TMA and HMA are derived from malic acid. Acetoxy succinic anhydride represents a convenient in situ equivalent of maleic anhydride.

Cellulose in nano-meter domain or aka nano-cellulose (NC) has enticed much attention from researchers. Segregated cellulose from sugarcane bagasse (SCB) was used in this study, and then hydrolyzed with 40, 50 and 60% sulfuric acid at 45 °C for 90, 30, and 20 min. The impact of the different treatment conditions was evaluated regarding nano-product yields and morphology aspects. The current study discusses the surface morphology, structural and elemental properties of nano-celluloses (NCs). Morphological; X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and elemental analysis; energy dispersive x-ray diffraction (EDX). Morphological characterization showed the figuration of stick-shaped rods and bundles of NCs with size in the ambit of about 34–49 nm. Elemental analysis (EDX) showed multiple elements in NCs with other major compositions. X-ray diffraction appeared that NCs have diverse crystallinity indices at different nanoscales. We have achieved the main challenges based on; The high concentration of acid used, the short reaction time needed and the smallest size using a 60% concentration of acid in a time of 20 min compared to other concentrations used in this study. Extracted NCs presupposed to have a high potency in many applications. Therefore, NCs are considered a modified biomass with great potential to meet global energy demand and encourage environmental sustainability.

Biomass valorization is gaining recognition as a sustainable and easily accessible renewable option to produce fuels and chemicals non-derived from fossil fuels, thus contributing to the decarbonization of the energy and chemical industries. Electrosynthesis represents a potent and advantageous method to transform biomass-based compounds into added-value products, surpassing conventional synthetic pathways in various aspects. Nevertheless, technical and geometrical constraints preclude its widespread implementation and development. Within this context, additive manufacturing has the potential to emerge as a disruptive technology in the field of electrochemical reactions, enabling the creation of custom-designed cells and reactors with intricate geometry. This perspective article delves into the applications of this innovative and widely accessible technology in organic electrosynthesis for biomass valorization, highlighting its potential to enhance performance, optimize mass transport phenomena, and facilitate the design of efficient and scalable electrochemical systems for various applications.

This review article discusses the potential of using metal-doped TiO₂ as a photocatalyst for dye degradation in water. TiO₂ is a promising photocatalyst but is limited due to its fast electron-hole recombination rate and vast bandgap energy. Metal dopants have enhanced the photocatalytic activity of TiO₂, especially noble metal doping, due to the synergistic effects between the metal dopants and TiO₂. The review summarizes experimental studies on photocatalytic dye degradation using metal-doped TiO₂ and compares the degradation performance between doped and undoped TiO₂. The authors emphasize the importance of understanding the interaction between metal dopants and TiO₂ to improve the dye degradation activity and stability of metal-doped TiO₂. The article highlights the optimum dopant concentration and preparation methods that can improve the textural or surface properties of doped TiO₂ and enhance dye degradation capacity.

The electrochemical conversion of biobased levulinic acid (LA) into renewable chemicals and biofuel precursors represents an important and reasonable alternative to the high temperature conventional catalytic processes of great importance for the development of a sustainable and cost-effective biorefinery. The establishment of the mechanism of levulinic acid reduction is a promising strategy in choosing the optimal electrocatalyst for the redox-transformation of biobased substrates. Herein, we report a new approach to study an electrochemical reduction mechanism of levulinic acid using of proton-deficient non-aqueous reaction media. The electrochemical reduction of levulinic acid to γ-valerolactone (GVL) and valeric acid (VA) in aqueous and organic solutions on various electrodes (glassy carbon, graphite, Al, Pb) was studied. The mechanism of LA electrochemical reduction and major reaction products significantly was found to depend on the solvent, the presence of proton donors, the material of cathode, and the magnitude of the applied potential. In an aqueous solution the process proceeded with the formation of valeric acid on all the electrodes studied. In acetonitrile in the presence of protons, the electrochemical reduction of LA proceeded by various mechanisms, both with the participation of atomic hydrogen and the protonated form of LA, and led to the formation of GVL and/or VA. The difference (ΔE_1/2) between the reduction half-wave potential of protons and levulinic acid was found to play an important role in the reduction pathway of LA carbonyl group. At a large ΔE_1/2, as in the case of the GC electrode, the LA reduction resulted in the GVL formation. LA can be completely reduced to VA by transferring four electrons due to the close reduction potentials of protons and LA (a low ΔE_1/2), as on a Pb electrode. The pathway depends on the conditions of the reduction process and can be estimated based on electrochemical data obtained in the study of reaction products in organic media.

One of the prominent issues of the environment is water quality deterioration due to release of industrial wastewater containing heavy metals. This research work focused on the synthesis of mesoporous magnetic iron oxide-aluminum silicate (Fe₃O₄-Al₂SiO₅) adsorbent via deposition-precipitation method and to assess its efficiency for chromium (VI) adsorption. The study demonstrated that the prepared mesoporous adsorbent exhibit large surface area (476.0 m²g^-1) and mesoporous structure, which enhances the adsorbate adsorption. From the results it was noticed that maximum removal (99.9%) was occurring at neutral pH and the adsorption data was find in best fitting to both Langmuir isotherm as well as with pseudo-second-order kinetic models. The study further concluded that the mesoporous adsorbent can be reused following several cycles and that very slight effect of coexisting competitive ions was noticed. The study recommends that after further modification and activation, the desired mesoporous adsorbent material could be utilized for water purification at industrial level.

Cellulose nanofibrils (CNFs) were produced from bleached eucalyptus kraft pulp using microfluidization varying the number of passes through the microfluidizer. CNFs were processed into dry films to elucidate the effect of CNFs morphology on the physical, optical and barrier properties of the films. As the number of passes through the microfluidizer increased, the fibril diameter and degree of polymerization decreased. A higher number of passes produced CNFs with smaller diameter resulting in CNF films with smaller root mean surface (RMS) roughness, higher tensile strength and Young's modulus, and higher transparency. CNF films with lower porosity had lower water vapor permeability (WVP) at 50% RH (better barrier properties), but the number of passes did not significantly affect water vapor permeability at 90% RH or oxygen permeability at 50% RH or 90% RH. Increasing the number of microfluidization passes resulted in CNF films with higher density, lower crystallinity, and higher water accessibility. The results suggest that the physical properties, such as density, of the film were more dominant for the mechanism of WVP compared with crystallinity and water accessibility. A model of water vapor transmission through the CNF film was proposed. By establishing a relationship between CNFs morphology and performance characteristics of corresponding films, especially for barrier properties, insights were obtained that would be beneficial for food packaging applications.

Corn starch film samples cross-linked using malic, malonic, and succinic acids, and thermoplastic starch were characterized and tested for their water absorption, surface morphology, structural change, and thermomechanical properties. The acids vary in acidity, number of hydroxyl groups, and carbon chain length. The presence of an additional hydroxyl group has helped malic acid form more hydrogen bonding between starch molecules. The relatively higher acidity in malic acid compared to succinic acid is found to be another factor for its better cross-linking potential. The additional carbon chain in succinic acid, which reduces its solubility and acidity; has negatively affected its cross-linking potential. Among the three variables studied, number of hydroxyl group has highly influenced the cross-linking potential, followed by acidity and carbon chain length, respectively. Consequently, the elongation at break and water absorption resistance of thermoplastic starch were improved from 108.63 ​MPa to 175.72 ​MPa and from 140% to 80%, respectively, cross-linking corn starch with malic acid.

Background

The objective of this research was to ascertain how the phenolic profile and associated antioxidant and antibacterial activities were affected by several solvents, including methanol, n-hexane, chloroform, ethylacetate, and water.

Methods

The dried coarse powder of the seeds was fractionated with various solvents after being extracted with methanol. Antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl and Nitric oxide scavenging tests, whilst antibacterial activity was evaluated using the disc diffusion technique.

Results

The outcomes indicate that ethyl acetate is the most efficient solvent for polyphenol extraction. The ethyl acetate fraction of Quercus leucotrichophora seed extract exhibited the greatest DPPH and NO radical scavenger antioxidant activity, with IC₅₀ values of 49.019 ± 0.15 μg/ml and 51.39 ± 0.19 μg/ml, respectively, whereas the aqueous fraction exhibited the lowest antioxidant potential. The Folin-Ciocalteu technique found that the ethyl acetate fraction had a greater phenolic content than the aqueous fraction (157 ± 0.27 mg of equivalent gallic acid (GAE)/g vs. 28 ± 0.28 mg GAE/g). Using an aluminum chloride colorimetric technique, the ethyl acetate fraction had the maximum flavonoid concentration (145 ± 0.37 mg quercetin equivalent QE)/g), whereas the aqueous extract had the lowest (13.1 ± 0.18 mg of QE)/g). In terms of antibacterial efficacy, the ethyl acetate fraction produced a wider inhibition zone against gram positive and gram negtive bacterial strains.

Conclusion

Based on the results, ethyl acetate fraction of Quercus leucotrichophora A. camus seed extract has significant antioxidant activity and may be a beneficial source of natural antioxidants and antibacterial for functional food composition.

A helpful manufactured course to the one-pot green synthesis of 2-amino-4H-chromenes through a tandem Knoevenagel-Michael cyclocondensation reaction of aldehydes, malononitrile, and resorcinol in polyethylene glycol (PEG-400) as accessible and biodegradable media have been detailed. All responses are completed in a brief time and the items are gotten in fabulous yields. The striking highlights of this eco-friendly approach are biodegradable media, fabulous yields, simple work-up without requires for column chromatographic separation, and no poisonous organic solvents, evasion of harmful reagents, one-pot strategy, and effortlessness of operation. Additionally, PEG-400 is exceedingly steady and can be reused for four sequential runs without major basic changes or misfortune of movement, which has been exceptionally advantageous in tending to natural concerns.