Current Microwave Chemistry - Current Issue

This study explores the effectiveness of microwave plasma pyrolysis in reducing heavy metal concentrations, specifically cadmium, in automobile shredder residue (ASR).

The ASR was subjected to plasma pyrolysis at microwave power levels ranging from 800 to 1000W, resulting in a significant decrease in heavy metal concentration in the char. Utilizing the Bureau Communautaire de Référence (BCR) sequential extraction method, a standardized procedure developed by the European Commission, we assessed the chemical speciation and matrix properties of the char. The results indicated that microwave plasma treatment effectively decreased the bioavailable forms of cadmium. After 6 minutes of pyrolysis at 1000W, the exchangeable and acid-soluble fractions (F1) dropped to 10%, while the reducible fraction (F2) fell to 12%.

This treatment resulted in a substantial increase in the oxidizable (F3) and residue (F4) fractions, which reached 27% and 51%, respectively. Importantly, the potential ecological risk of cadmium decreased significantly, with the risk index (Er) dropping from 164.91 to 28.45, aligning with Taiwan's regulatory standards for non-hazardous waste.

These findings suggest that microwave plasma pyrolysis is a promising and sustainable approach for the disposal of ASR, offering an environmentally friendly alternative for waste management. This study provides valuable insights for policymakers, environmental scientists, and industries seeking effective solutions for ASR treatment.

This study evaluates the efficiency of essential oil extraction from Elsholtzia Cristata (EC) using two methods: the classical steam distillation method (CM) and the microwave-assisted extraction method (MM). The focus is on comparing these methods in terms of essential oil yield and assessing the antimicrobial properties of the extracted oils, particularly the antibacterial activity of citral.

The study evaluates which extraction method yields higher essential oil content and better preserves bioactive compounds, with a focus on the antibacterial activity of citral. It also explores the potential pharmaceutical applications of the essential oil.

Essential oils were extracted from EC using both CM and MM. The essential oil content was measured over different extraction times. Gas Chromatography-Mass Spectrometry (GC-MS) was used to identify the chemical constituents of the oils. Citral isolation efficiency was determined using bisulfite. Antimicrobial testing was performed to evaluate the antibacterial activity of EC essential oils against various bacterial strains.

The MM yielded a higher essential oil content (0.47% after 10 minutes) compared to CM (0.4% after 3 hours). GC-MS analysis identified citral A and citral B as the major components of the essential oil. The optimal molar ratio of citral to bisulfite for effective isolation was 1:3, achieving an 86% efficiency. Both EC essential oil and citral exhibited strong antibacterial activity against a range of bacterial strains.

The microwave-assisted extraction method demonstrated superior efficiency in extracting essential oils from EC, with higher yields and shorter extraction times compared to the classical method. The significant antibacterial activity of EC essential oil indicates its potential for use in pharmaceutical and healthcare applications.

Synthetic dye removal from wastewater poses significant environmental challenges. Metal-organic Frameworks (MOFs), like ZIF-8, offer potential solutions due to their high adsorption capacities. This study has investigated the efficacy of a novel composite material, α-Al2O3@ZIF-8, for Methylene Blue (MB) removal.

This study aimed to assess the feasibility of α-Al2O3@ZIF-8 for MB removal. The synthesis via microwave-assisted methods, physicochemical characterization, adsorption efficiency evaluation, and isothermal/kinetic modeling, has been conducted.

The α-Al2O3@ZIF-8 composite was synthesized and characterized using SEM, TEM, FTIR, and BET techniques. The adsorption efficiency for MB was tested, and isothermal/kinetic models were applied for mechanistic understanding.

The composite exhibited robust crystal connections and uniform distribution, with particle sizes ranging from 0.5 to 0.6 µm. MB adsorption efficiency exceeded 97.8% under optimal conditions. Isothermal and kinetic modeling revealed favorable adsorption behavior, notably with the Langmuir and pseudo-second-order models.

Microwave-synthesized α-Al2O3@ZIF-8 shows promise for efficient MB removal, with treatment efficiencies surpassing 97%. This underscores the potential of MOFs in wastewater treatment and emphasizes the importance of understanding adsorption mechanisms for optimization.

The purpose of this study was to investigate the molecular interactions between urea and dextran.

The molecular interaction was examined using an ultrasonic method.

The objective of the study was to use measurable data such as density, viscosity, and ultrasonic velocity to determine the thermoacoustical parameters. The kind and intensity of polymer molecular interactions as a function of temperature and concentration at various frequencies have been extensively assessed using the ultrasonic approach. The viscosity (η), density (d), and ultrasonic speed (U) of polymer dextran and aqueous 6(M) urea were measured throughout a temperature range of 303 K to 323 K at 5 K intervals.

A specific gravity bottle, an Ostwald viscometer, and an ultrasonic interferometer were used to determine the density, viscosity, and ultrasonic velocity, respectively.

The obtained thermo acoustic parameter suggests the presence of a molecular interaction in the investigated solution.

Solute-solvent interactions make up the bulk of interactions. The dynamics of molecular interactions change with frequency, resulting in less favorable and less efficient interactions at higher frequencies. The analysis revealed that changes in frequency and temperature produce specific differences in acoustic parameters.

Resveratrol is a polyphenolic compound found in plants such as Polygonum cuspidatum, Veratrum nigrum L. and Gnetum montanum Markgr. It has unique functions and biological activities. It has important physiological effects such as anti-cancer, anti-bacterial, lipid-lowering, and prevention of cardiovascular and cerebrovascular diseases. At present, resveratrol is a new type of medicinal and healthcare-active substance, with the potential to develop into a new anti-cancer drug and a new ingredient for healthcare products.

The purpose of this study is to seek the optimal extraction process for resveratrol from the root of Veratrum nigrum L.

The microwave-assisted extraction method (MAE) was used to extract resveratrol from the root of Veratrum nigrum L. and orthogonal experiments were conducted to optimize the extraction process. The results of the microwave-assisted extraction, ultrasonic extraction, and their combined use methods were compared with those of the conventional heating reflux method. At the same time, the extraction data of four plants, including Polygonum cuspidatum, Veratrum nigrum L., Gnetum montanum Markgr. and Blueberry, were compared.

Under the optimized microwave-assisted extraction conditions, the best process conditions for the root of Veratrum nigrum L were a solid-liquid ratio of 1:20 (g/mL), at a microwave power of 600W, affording an extraction rate as high as 2.7130 (mg/g), within an extraction time of 10 minutes. It is higher than the extraction rate of 2.2911 (mg/g) obtained by the conventional heating reflux method.

This study indicates that microwave-assisted extraction is an efficient method with a high extraction rate of resveratrol during short extraction time. It is a green and environmentally friendly extraction technique, and it is recommended for the extraction of active substances such as resveratrol from plants.

Microwave-assisted reactions align with the principles of green chemistry by significantly reducing synthesis time, avoiding high temperatures, and typically yielding high product quantities.

A catalyst was synthesized from waste banana peels, ensuring both availability and low-cost production. Ethers were synthesized using microwave irradiation at 300 W, employing two different alkyl halide variants with both substituted and unsubstituted phenols.

The reaction proceeded efficiently without the need for corrosive bases such as caustic soda or caustic potash. Microwave irradiation facilitated reduced reaction times for ether formation. Additionally, the supported catalyst demonstrated the advantage of reusability.

This protocol offers several benefits, including the use of a green solvent and the exclusion of phase transfer catalysts and harsh conditions. Consequently, an efficient and green synthesis of ethers has been achieved.

This paper presents a detailed overview of the synthesis and spectroscopic characterization of azocalix[4]resorcene using microwave assistance. Compared to traditional methods, this microwave approach is not only faster but also more energy-efficient. Plus, it gives higher yields (20-24% more yields).

The synthesized compounds are characterized using various spectroscopic techniques. These include mass spectrometry, elemental analysis, FT-IR, & NMR. Through extensive spectroscopic analysis, we confirm both structural and functional properties.

The findings highlight the advantages of utilizing microwave-assisted synthesis in producing azocalix[4]resorcinarene. This study highlights the advantages of microwave-assisted synthesis in producing structurally complex and biologically active molecules efficiently. Additionally, we conducted tests to evaluate the antibacterial and antifungal properties of these compounds. The study evaluated the efficacy of the synthesized compounds against Aspergillus niger, Rhizopus sp., Escherichia coli, and Staphylococcus aureus. Antimicrobial activity tests revealed significant inhibitory effects against Aspergillus niger and Rhizopus sp., while the antibacterial assays demonstrated inhibition zones of 12 mm for Escherichia coli and 9 mm for Staphylococcus aureus.

These results underscore the potential of azocalix[4]resorcinarene as a versatile compound with promising antimicrobial properties.