Plasma Chemistry and Plasma Processing最新文献

Plasma technology for generating activated water has garnered significant interest among researchers for its antimicrobial properties post-treatment. This study aimed to produce chitosan hydrogels incorporating various types and concentrations of plasma activated water (PAW) derived from tap water and purified water. Initially, the physicochemical properties of PAW, including pH, electrical conductivity (EC), and total dissolved solids (TDS), were assessed, revealing a notable decrease in pH and an increase in EC and TDS post-activation. Chitosan hydrogels were then synthesized using PAW and subjected to Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) analyses. Results indicated a minimal impact on the chemical structure of the hydrogels post-PAW addition. TGA and DSC results revealed differences between tap water-based hydrogels and purified water-based hydrogels, indicating the presence of impurities or minerals in tap water. SEM observations depicted morphological alterations with increased plasma exposure, potentially enhancing antimicrobial activity. In degradation and swelling tests, the hydrogels exhibited pH sensitivity, maintaining integrity in neutral and alkaline media while dissolving in acidic conditions. Hemocompatibility and antimicrobial efficacy were confirmed through hemolysis tests and antibacterial/antifungal assays, particularly in hydrogels with prolonged water activation times, attributed to reactive species in PAW. These findings underscore the potential of these hydrogels as disinfectants in the biomedical field.

A process of CO₂ decomposition in dielectric barrier discharge reactor using mesoporous CeO₂-NiO catalysts was studied. Mesoporous materials of MCM-41, SBA-15 and MCF types were used in this study to investigate the influence of the material structure on CO₂ decomposition efficiency. The obtained catalysts were characterized by physico-chemical methods: low temperature N₂ adsorption, X-Ray diffraction and X-Ray photoelectron spectroscopy. CO₂ conversion, CO yield and CO selectivity as well as energy efficiency and specific energy input were calculated. The comparison of process efficiency was conducted with that in the absence of any catalyst (plasma-only reactor). It was shown that in the presence of Ce-based catalysts, the conversion of CO₂ (from 11 to 19%) and CO yield rise significantly, while CeNi samples show minor performance in CO₂ plasma-catalytic dissociation. Porous characteristics affected the performance of CO₂ decomposition. Using wide-porous MCF-type material as a support, it was possible to achieve the highest conversion due to enhanced CO₂ adsorption in pores and subsequent plasma-catalytic decomposition. The combination of mesoporous silica material as a support and a CeO₂ as an active component is promising for the plasma-catalytic CO₂ splitting.

Sustainable agriculture requires the exploration and development of eco-friendly technologies to increase crop production. From the last few decades, nonthermal atmospheric pressure plasma (NTAPP) based technology appears as an encouraging frontier in this quest. NTAPP with low temperature and energetic gas-phase chemistry offers potential applications to promote seed germination rate and plant growth. It initiates a cascade of biological responses at molecular levels inside the seed as well as in plants, greater nutrient uptake, elevated antioxidant activity, and pathogen control to ensure improved germination, seedling growth, plant growth, and increased harvesting. NTAPP technology has become more popular and convenient in agriculture due to its potential to produce plasma-activated water (PAW), which harnesses useful reactive species with PAW irrigation to promote plant growth. Recent advancements in NTAPP technology and its applications to promote seed germination, seedling growth, plant growth, and metabolite synthesis were summarized in this review. We delve deeper to examine the possible mechanisms that underlie the involvement of reactive species from NTAPP, surface interactions, and gene expression regulation. We also have discussed the applications of NTAPP in seed priming, pre-planting treatments, and disease control for food preservation. For sustainable agriculture, NTAPP stands out as an eco-friendly technology with the potential to revolutionize crop production of the modern age. Many researchers proved that NTAPP reduces the need for agrochemicals and presents a viable path toward sustainable agriculture. This review will provide recent progress by outlining major challenges and shaping future directions for harnessing the potential of NTAPP in agriculture.

The study investigates the efficacy of plasma-activated water (PAW) in preserving green chillies (jalapeño and pusa jwala) and compared it with various household fruits and vegetables cleaners’ solutions. PAW was prepared using a pencil plasma jet with air as the plasma forming gas. The results of visual analysis revealed that PAW-treated chillies maintain their fresh appearance even after 21 days, exhibiting significantly lower spoilage compared to control (ultrapure milli-Q water) and fruits and vegetables cleaners’ solutions. PAW demonstrated antimicrobial properties, effectively reducing microbial growth and spoilage on chillies over the storage period. Physical attributes, such as weight loss and firmness, are evaluated. It has been observed that PAW-treated chillies exhibit lower weight loss and higher firmness, indicating better membrane integrity and moisture retention. Microbial resistance was notably higher in PAW-treated chillies compared to control and when cleaning solutions were used. CIELAB color analysis revealed that PAW-treated chillies retain greenness, and color, freshness, outperforming control and cleaners. Sensory evaluation, including visual inspection, smell, taste, and touch, consistently favored PAW-treated chillies, emphasizing their superiority in terms of enhancement in shelf-life. Biochemical analysis revealed that PAW-treated chillies either maintain or show enhancement in nutritional attributes such as soluble sugar, protein, and ascorbic acid concentrations. Phenol concentration (antioxidant activity) remained stable across treatments. Overall, the study underscores the positive impact of PAW treatment on preserving the membrane integrity, antimicrobial resistance, sensory quality, and nutritional attributes of green chillies, making PAW an alternative for extending their shelf life.

The combination of plasma technology with microfluidics has gained significant attention in recent years. The unique characteristics of microfluidic chips, such as high surface-to-volume ratio and efficient mass transfer, coupled with plasma’s ability to provide the necessary green energy for the degradation of complex molecules, make this combination promising for water and wastewater treatment applications. A gas/liquid biphasic dielectric barrier discharge (DBD) plasma microreactor powered by a nano-pulsed excitation source, at atmospheric pressure, was used to study the degradation of p-benzoquinone and caffeine in water, chosen as model molecules for water pollution. Based on High Performance Liquid Chromatography (HPLC) analyses, the argon plasma was able to completely degrade both molecules at concentrations 10^− 5, 10^− 4 and 10^− 3 mol/L. At higher concentration (10^− 2 mol/L), the plasma promotes the synthesis of hydroquinone from p-benzoquinone. A 50% mineralization is achieved after plasma for the caffeine in aqueous solution at 10^− 5 M.

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al₂O₃ are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C₂₊ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 (:text{M}text{J}:{text{m}text{o}text{l}}_{text{C}{text{H}}_{4}}^{-1}) and from 9 to 4.7 (:text{M}text{J}:text{m}text{o}{text{l}}_{{text{C}}_{2+}}^{-1}). Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Plasma activated water (PAW) has been prepared using atmospheric pressure air dielectric barrier discharge with the bubbling method. This study aims to elucidate the crucial role of gas-liquid interface in determining the physicochemical properties and biological reactivity of PAW, as well as describe the process of mass transfer for reactive oxygen and nitrogen species (RONS) during the PAW generation. Gas-liquid interfacial area is regulated by varying the airflow rate. When the airflow rate increases from 0.5 to 16.0 SLM, the concentrations of (:text{N}{text{O}}_{text{2}}^{text{-}}), (:text{N}{text{O}}_{text{3}}^{text{-}}), (:{text{O}}_{text{3}}) and activated oxygen in PAW increase significantly, and the water-activated time for complete E. coli inactivation can be shortened from more than 320 s to 40 s. The numerical simulation result shows that when the airflow rate increases from 0.5 to 16.0 SLM, the gas-liquid interfacial area increases from 0.014 to 0.3 m²/600 mL. The analysis shows that the dependence of the chemical reactivity and the biological reactivity on the interface area is mainly attributed to the change of the mass flux with the interface area.

Nonthermal plasma (NTP) is an efficient treatment technology for cooking fumes (CFs). However, its practical implementation is hindered due to the low mineralization rate of CFs and high generation of by-products. In this study, a hybrid system coupling NTP and Mn/HZSM-5 catalysts was developed for the deep oxidation of CFs. These catalysts exhibited a remarkable synergistic effect together with NTP in improving the efficiency of CFs removal. When the specific energy density was 282 J·L^− 1, the hybrid system had stable reactivity, and the CFs removal efficiency and CO₂ yield were 100% and 78.4%, respectively, which were 10% and 61% higher than the values achieved with the NTP system alone. The Mn/HZSM-5 catalysts were also discovered to inhibit the production of O₃ and NO₂ to a large extent and to achieve a removal efficiency level at > 80%. The Mn/HZSM-5 catalysts’ high Mn⁴⁺/Mn ratio and the relatively large amount of chemisorbed oxygen on the catalyst surface engendered their remarkable performance. On the basis of the detected active species and organic products, the reaction mechanism governing the destruction of CFs by the NTP-Mn/HZSM-5 catalyst system was also discussed.

The synthesis of ammonia using non-thermal plasma can present distinct advantages for distributed stand-alone operations powered by electricity from renewable energy sources. We present the synthesis of ammonia from nitrogen and hydrogen using a membrane Dielectric-Barrier Discharge (mDBD) reactor integrated with metal catalyst. The reactor used a porous alumina membrane as a dielectric-barrier and as a distributor of H₂, a configuration that leads to greater NH₃ production than using pre-mixed N₂ and H₂. The membrane is surrounded by catalyst powder held by glass wool as porous dielectric support filling the plasma region. We evaluated nickel, cobalt, and bimetallic nickel-cobalt as catalysts due to their predicted lower activation energy under non-thermal plasma conditions as determined through Density Functional Theory (DFT) calculations. The catalysts were loaded at 5% by weight on alumina powder. The performance of the catalytic mDBD reactor was assessed using electrical, optical, and spectroscopic diagnostics, as well as Fourier-Transform Infrared spectroscopy. Experimental results showed that the glass wool support suppresses microdischarges, generally leading to greater ammonia production. The Ni-Co/Al₂O₃ catalyst produced the greatest energy yield of 0.87 g-NH₃/kWh, compared to a maximum of 0.82 and 0.78 g-NH₃/kWh for the Co/Al₂O₃ and Ni/Al₂O₃ catalysts, respectively. Although the differences in performance among the three metal catalysts are small, they corroborate the predictions by DFT. Moreover, the maximum energy yield for bare Al₂O₃ (no metal catalyst) with dielectric support was 0.38 g-NH₃/kWh, for mDBD operation with no metal catalyst or dielectric support was 0.28 g-NH₃/kWh, and for standard DBD operation (no membrane, dielectric support, or catalyst) was 0.08 g-NH₃/kWh, i.e., 2.1, 3.1, and 11 times lower, respectively, than the maximum energy yield for the Ni-Co/Al₂O₃ catalyst with dielectric support. The study shows that the integration of dielectric membrane and metal catalyst is an effective approach at enhancing ammonia production in a DBD reactor.

Synthesis of W nanoparticles by magnetron sputtering combined with gas aggregation operated in Ar suffers from a continuous decrease of the synthesis rate, ceasing in a finite time interval, in the range of minutes to tens of minutes. Experimentally, we noticed that adding small amounts of H₂ to Ar (5–20%) increases the synthesis rate, which remains constant over time, at a value dependent on the amount of injected hydrogen. Mass spectrometry investigations revealed, in the hydrogen presence, a dominance of the ArH⁺ ions over the Ar⁺ ones, associated also with an increased number of W⁺ and WH⁺ species in plasma, sustaining a substantial increase in the nucleation rate.