Current Research in Green and Sustainable Chemistry最新文献

Solanesol (C₄₅H₇₄O) is an aliphatic terpene alcohol of nine isoprene units found in the tobacco plant (Nicotiana Tabacum L.). The long and complex biosynthetic pathway of solanesol makes the extraction method still the best way to obtain solanesol. This work evaluates the optimum conditions for sequential extraction from tobacco leaves using microwave-ultrasound-assisted extraction (MUAE) as a green extraction method. There were two stages of extraction (sequential): first, microwave-assisted extraction (MAE), followed by ultrasound-assisted extraction (UAE). At the MAE stage, dry tobacco powder was extracted with variations of water-to-solid (feed) ratio (S/F) from 1:1 to 10:1 (mL/g), power from 200 to 800 W, and time from 0.5 to 2 min. Optimum conditions were obtained at 6:1 (mL/g), 400 W, and 1.5 min, respectively. The UAE stage was fixed with the solvent-to-solid (feed) ratio (S/F), solvent ratio (v/v), time, and temperature of 40:1, 1:2 (PE:ethanolic acid), 30 min, and 40 °C, respectively. The optimum solanesol yield was 3.0 % (w/w), and a nicotine yield of 1.41 % (%w/w) was obtained under the same conditions. The resulting crude solanesol was then purified using silica gel column chromatography (CC), resulting in a purity of 85 %. The yield of extracted solanesol is much higher than in other studies due to the use of fresh leaves and MUAE method.

Caffeic acid (CAF) i is a polyphenolic compound commonly found in plants, valued for its ability to act as an antioxidant. This study focused on investigating the impact of a natural antioxidant, specifically caffeic acid (CAF), compared to two synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), on the thermal stability of propylene/ethylene copolymer (C-PP/PE), Aiming to establish a theoretical framework for the advancement of novel polymeric antioxidant compounds. Theoretical calculations were conducted to determine each compound's thermodynamic properties and antioxidant activity. The phenolic hydroxyl bond dissociation enthalpy (BDE) values revealed that BHA had the lowest value (325.6 kJ mol⁻¹), trailed by CAF (328.2 kJ mol⁻¹) and BHT (341.3 kJ mol⁻¹), indicating a higher electron-donating capacity of BHA. Transition energy (TS) calculations indicated that BHA had the lowest TS energy (49.29 kJ mol⁻¹), succeeded by CAF (57.61 kJ mol⁻¹) and then BHT (75.57 kJ mol⁻¹), suggesting greater efficiency in radical scavenging. Additionally, the obtained rate constants showed that CAF had the highest hydrogen abstraction rate (k = 1.05 × 10⁵ M⁻¹ s⁻¹), followed by BHA (k = 1.17 × 10⁴ M⁻¹ s⁻¹), and then BHT (k = 4.2 × 10³ M⁻¹ s⁻¹). These results support the effectiveness of CAF as a potentially more active antioxidant. In the experimental part of this study, it was observed that C-PP/PE with BHA showed a lower melt flow index (MFI) (8.51), indicating more excellent thermal stability. On the other hand, samples containing natural caffeic acid extracts exhibited a gradual decrease in MFI with increasing CAF concentration (MFI of 9.4, 8.82, 7.59, 6.44, and 5.98 for concentrations of 0.025, 0.05, 0.075, 0.1, and 0.125 ppm, respectively), suggesting a progressive improvement in the thermal stability of C-PP/PE with increasing natural antioxidant. In TGA analyses, decomposition was observed around 340 °C in samples without additives and those containing 0.1 ppm of BHA. In contrast, samples with different concentrations of CAF showed delayed degradation, observed in the temperature range of 380–400 °C. This delay in degradation indicates that CAF imparts more excellent thermal stability to C-PP/PE copolymer, as it reaches temperatures above 400 °C before starting its decomposition. These findings support the feasibility of using natural antioxidants such as CAF to improve the thermal properties of copolymers.

Polyethylene terephthalate (PET) use has increased, causing more PET trash and environmental and health issues. Disposal and burning alone cannot solve this problem. Thus, PET recovery methods with low byproducts are the priority. The recycling rate is still below 30%, so different cleaning methods are being investigated. Therefore, studies have focused on extracting terephthalic acid from PET bottles for MOF synthesis to reduce their cost of production. Herein, MIL-101(Cr) was synthesized from PET bottles and used as a solid catalyst for oleic acid esterification with methanol to produce methyl oleate (biodiesel), an alternative energy source to fossil fuels—the highest biodiesel yields at 1:39 molar ratio of oleic acid to MeOH, 6 wt% loading, 65 °C, and 4 h reactions time were attained at 86.9 and 80% for MIL-101(Cr) on a pristine and scrap basis, respectively. The kinetic study revealed that activation energies were 25.27 kJ/mol and 28.3 kJ/mol for original and waste-derived MIL-101(Cr). The waste-derived MIL-101(Cr) was reused three times while five-time cycles for the original MIL-101(Cr).

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.

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.

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.