Current Research in Green and Sustainable Chemistry最新文献

Water bodies are being threatened continuously by various anthropogenic pollutants such as organic dyes and bacteria which led to scarcity of fresh water suitable for drinking and irrigation. Therefore, different water treatment methods have been implemented before the discharge of contaminated wastewater into water bodies. In this report, green-synthesized silver nanoparticles (AgNPs) were evaluated in the degradation of organic dyes and bacterial decontamination. The S. costus root aqueous extract was used as an environmentally benign reducing agent in the biosynthesis of AgNPs. The synthetic procedure was optimized in terms of different parameters, and several analytical techniques were used to thoroughly characterize the prepared nanocomposites including TEM, SEM, EDX, DLS, XRD, FTIR, UV/Vis, photoluminescence, and TGA. The nanoparticles were spherical, monodisperse, colloidally and thermally stable, and crystalline in nature. The efficiency of the biogenic AgNPs as catalysts for the degradation of organic dyes was evaluated against six structurally diverse dyes. These included methylene blue, phenol red, methyl orange, Congo red, orange G and safranin O. Moreover, the applicability of AgNPs as antibacterial agents was tested against K. pneumoniae, S. aureus, S. haemolyticus and E. faecalis where the zones of growth inhibition, MIC and MBC values were determined for each bacterium. Overall, the biosynthesized nanoparticles were remarkable catalysts in the discoloration of hazardous dyes and displayed notable antibacterial potency against Gram-positive and Gram-negative bacteria.

Poly(3-hydroxybutyrate) (PHB), a bio-produced and biodegradable polymer, has great potential as a replacement for petroleum-based polymers in many applications. However, strategies for the extraction and processing of PHB still require improvement. Switchable solvents, which can be toggled between hydrophobic and hydrophilic forms by the addition or removal of carbon dioxide in the presence of water, are easily recyclable and may improve PHB processing methods. Here, we have shown the ability to dissolve PHB in two switchable solvents (N,N-dimethylbenzylamine and N,N-dimethylcyclohexylamine), precipitate PHB by the addition of water and carbon dioxide, and recycle the solvent for subsequent dissolution and precipitation cycles. We have also demonstrated the ability for N,N-dimethylbenzylamine to form gels with PHB which maintain their water/solvent content as the solvent is switched to a hydrophilic form. These results demonstrate the usefulness of switchable solvents as a recyclable platform for PHB processing and their ability to create unique materials.

A novel, uncomplicated, and cost-effective methodology has been devised for the rapid synthesis of novel lower-rim-connected bisresorcinarene macrocycles. The incorporation of sodium p-styrenesulfonate (NaSS) facilitates the generation of a diverse array of products on a large scale, achieving high yields. Notably, the utilization of NaSS obviates the need for corrosive acids, and the absence of toxic solvents renders this reaction both environmentally friendly and economically advantageous. Furthermore, the process eliminates the necessity for column chromatography in product purification. The structural characterization of the synthesized derivatives was confirmed through comprehensive analyses, including FT-IR, ¹H NMR, ¹³C NMR, HR-Mass, and CHNO techniques.

Heterogeneous photocatalysis operated under visible light is considered an efficient and ecofriendly method to remove pharmaceuticals from water streams. However, the recovery of the nano-sized catalyst particles limits this technology to small-scale applications. In this study, we prepared Fe-doped P25 TiO₂ photocatalysts and immobilized them over PVDF-HFP electrospun membranes for the photocatalytic degradation of Tetracycline antibiotic under visible light. To ensure uniform distribution of the nanoparticles on the fibers, the electrospinning voltage and the weight percentage of TiO₂ were varied, and two preparation methods were applied to disperse the catalyst in the polymeric solution. In order to maximize the visible light exposure of the membranes, 3D printed membrane holders with square and circular shapes were designed to immerse the membrane in Tetracycline solution. The results showed that immobilizing P25 catalysts on the fibers of the membranes limited their visible light absorption when the light source was assembled on the top of the aqueous reaction medium. This occurred due to the membrane's opacity limited light penetration, resulting in uneven irradiation throughout its depth. Based on this, a new photocatalytic reactor design was proposed with immersed light illumination source to reduce the distance between the membrane and the light source for improved activation of the P25 particles. In this design, a 3D-printed vertical membrane holder was also included to accommodate a larger membrane surface area and therefore minimize the required spatial area for large industrial applications.

Torrefaction is a promising method of treatment with a prospect toward Physco-chemical improvement and thermal upgrading of biomass. In the present study, the torrefaction of sugarcane bagasse in both dry and chemical treatment in comparison with the physical, chemical, and thermal properties of raw bagasse was investigated. Thermochemical torrefaction was carried out by pretreatment of raw bagasse with dilute sulfuric acid. The torrefaction temperature was carried out at a carried temperature (220–280 °C) and a torrefaction period (30–120 min) in a packed bed reactor under an inert environment, whereas dry torrefaction was performed using the same treatment without the addition of a chemical to the raw bagasse. Chars produced by chemical torrefaction were found with improved properties of heating value, energy, and bulk density at 280 °C and 120 min. Increasing temperature resulting in high fixed carbon content apparently decreases moisture content and volatile matter. The mass yield and energy yield were found to be decreased with temperature and time. The carbon content of torrefied bagasse was increased with temperature and time, whereas, hydrogen and oxygen content decreased due to the devolatilization reactions. It was able to upgrade HHV from 16.05 to 20.34 MJ/Kg in dry and 22.29 MJ/Kg in chemical torrefaction.

This research delves into the analysis of essential oil derived from Citrus limon leaves cultivated in the northern region of Bangladesh, focusing on their potential attributes. The essential oil was extracted employing a microwave-assisted gravity station without using solvent. Optimization was carried out in terms of time, temperature and power as a function of oil yield. The study revealed the highest oil yield of 2.5 % after 50 min at 110 °C, maintaining a microwave power of 300 watt. Twenty-four (24) phyto-components were identified by Gas Chromatogram- Mass Spectrometer (GC-MS) where d-Limonene (34.10660 %) was dominant compound. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to assess the antioxidant activity of essential oil. Notably, essential oil displayed superior DPPH radical scavenging activity (IC₅₀ 8.57 ppm) compared to butylated hydroxytoluene (BHT) (IC₅₀ 10.63 ppm), a common antioxidant standard. Furthermore, a variety of harmful microorganisms were used to evaluate the antimicrobial efficacy. The extracted essential oil exhibited the strongest antimicrobial effectiveness against bacteria Staphylococcus aureus (ZOI-27.50 mm, MIC-7.8 μL/mL) and the fungi Candida albicans (ZOI-32.83 mm, MIC-1.95 μL/mL). These findings demonstrate the Citrus limon leaves essential oil contains bioactive components with strong antioxidant and antimicrobial properties. The extracted essential oil holds significant potential for applications in the foods, pharmaceuticals and cosmetic industries.

The presence of chemically different and compositionally varying plastics in mixed postconsumer recovered plastic (PCR) presents daunting barriers to recycling and upcycling efforts. This review systematically outlines how different processing techniques and characterization methods can be implemented to improve PCR's mechanical recycling and upcycling processes. The review further addresses the recycling challenges in the processing of mixed plastics from PCR and how their mechanical properties can be enhanced by making use of different types of compatibilizers such as copolymers, Janus nanoparticles as well as different approaches such as solid-state pulverization and microfibrillarization. In addition, the state-of-the-art applications of recycled plastics usage in automotive and construction are reviewed.

TiO₂ nanomaterial photocatalysts for energy and environmental applications have attracted the interest of researchers in recent decades. The broad bandgap (3–3.2 eV), which limits the quantity of light absorption, and the relatively high charge-carrier recombination, which limits photocatalytic activity, are the key bottlenecks. The discovery of black TiO₂ in 2011 sparked global research attention and renewed optimism for solving this challenge. The presence of defects such as Ti³⁺ species and oxygen vacancies at the surface of black TiO₂ nanostructures – so called due to the color assumed by the oxide following a reduction process - is responsible for enhancing the optical absorption of UV to visible light. This review focuses on recent advancements in the development of black TiO₂ nanomaterials, including description of the synthesis processes, focused on plasma and thermal methods to convert TiO₂ to black TiO₂, discussion of black TiO₂ properties, and diverse applications of black TiO₂, and concludes by addressing some essential concerns that must be tackled to unleash the desired future developments, particularly for solar energy production and pollutants decomposition.

In this study, the choice of supercritical fluid extraction as a renewable alternative for extracting orange peel essential oil (OPEO) was motivated by concerns about sustainability with conventional solvent extraction methods. The physical and chemical characteristics of OPEO were examined to assess its potential as a sustainable resource. The extraction process was optimised, and the ideal conditions determined were 317.51 min of extraction time at 74.85 °C with a solvent-to-sample ratio of 4. Analysis of the extracted OPEO revealed significant values for saponification (121.67 mg KOH/g), acid (4.13 mg KOH/g), ester (117.54 mg KOH/g), and free fatty acid (1.56 mg KOH/g) content, demonstrating its composition. Notably, key ingredients such as Limonene (43.96%), α-pinene (15.60%), β-myrcene (10.21%), γ-terpinene (5.00%), and α-terpineol (4.15%) were found in high proportions according to chemical composition analysis. Furthermore, OPEO exhibited excellent antioxidant properties with an IC50 value of 7.73 ± 2.00 mg/mL and displayed notable antimicrobial activity against various microorganisms, including P. aeruginosa (17.7 ± 0.6 mm), E. coli (11.0 ± 0.0 mm), K. pneumoniae (10.7 ± 0.6 mm), and S. aureus (10.3 ± 0.6 mm). These findings have significant implications for the flavor and fragrance sector, as well as for the food preservation industry.