Efficient degradation of p-nitrophenol from water by enhancing dielectric barrier discharge (DBD) plasma through ozone circulation: Optimization, kinetics and mechanism

Non-thermal dielectric barrier discharge (DBD) plasma has received great attention for degradation of persistent organic pollutants such as p-nitrophenol (PNP). However, the feasibility of the DBD implementation is not clear due to its high energy consumption and relatively low degradation efficiency. In this research, a novel strategy was suggested based on re-circulation of the generated O3 in the DBD system to enhance the PNP degradation efficiency and energy yield. The potential mechanism and possible pathway of PNP degradation were studied by EPR, ESR, DFT and GS-MS analytical tests. According to the results, the PNP degradation efficiency and energy yield increased from 57.4% to 94.4% and from 0.52 to 1.18 g kW-1h-1, respectively through ozone circulation into the DBD reactor. This was due to the more release of long-lived and short-lived reactive species (ROS) in the DBD-O3 system by the O3 circulation. The variations in pH (4 - 10), initial concentration (50 - 90 mg L-1), and the presence of co-existing substances in the water matrix had minimal impact on the DBD-O3 system, in comparison to the conventional system. The biological toxicity evaluation revealed that the hybrid DBD-O3 system transform PNP to less toxic intermediates. This study proposes a promising strategy to improve the utilization of DBD for the degradation of PNP.

Evaluation of degradation efficacy and toxicity mitigation for 4-nitrophenol using argon and air-mixed argon plasma jets

This paper investigates the effects of argon (Ar) and that of Ar mixed with ambient air (Ar-Air) cold plasma jets (CPJs) on 4-nitrophenol (4-NP) degradation using low input power. The introduction of ambient air into the Ar-Air plasma jet enhances ionization-driven processes during high-voltage discharge by utilizing nitrogen and oxygen molecules from ambient air, resulting in increased reactive oxygen and nitrogen species (RONS) production, which synergistically interacts with argon. This substantial generation of RONS establishes Ar-Air plasma jet as an effective method for treating 4-NP contamination in deionized water (DW). Notably, the Ar-Air plasma jet treatment outperforms that of the Ar jet. It achieves a higher degradation rate of 97.2% and a maximum energy efficiency of 57.3 gkW-1h-1, following a 6-min (min) treatment with 100 mgL-1 4-NP in DW. In contrast, Ar jet treatment yielded a lower degradation rate and an energy efficiency of 75.6% and 47.8 gkW-1h-1, respectively, under identical conditions. Furthermore, the first-order rate coefficient for 4-NP degradation was measured at 0.23 min-1 for the Ar plasma jet and significantly higher at 0.56 min-1 for the Ar-Air plasma jet. Reactive oxygen species, such as hydroxyl radical and ozone, along with energy from excited species and plasma-generated electron transfers, are responsible for CPJ-assisted 4-NP breakdown. In summary, this study examines RONS production from Ar and Ar-Air plasma jets, evaluates their 4-NP removal efficacy, and investigates the biocompatibility of 4-NP that has been degraded after plasma treatment.

Study of Iron Complex Photosensitizer with Hollow Double-Shell Nano Structure Used to Enhance Ferroptosis and Photodynamic Therapy

Ferroptosis therapy, which uses ferroptosis inducers to produce lethal lipid peroxides and induce tumor cell death, is considered a promising cancer treatment strategy. However, challenges remain regarding how to increase the accumulation of reactive oxygen species (ROS) in the tumor microenvironment (TME) to enhance antitumor efficacy. In this study, a hyaluronic acid (HA) encapsulated hollow mesoporous manganese dioxide (H-MnO2 ) with double-shell nanostructure is designed to contain iron coordinated cyanine near-infrared dye IR783 (IR783-Fe) for synergistic ferroptosis photodynamic therapy against tumors. The nano photosensitizer IR783-Fe@MnO2 -HA, in which HA actively targets the CD44 receptor, subsequently dissociates and releases Fe3+ and IR783 in acidic TME. First, Fe3+ consumes glutathione to produce Fe2+ , which promotes the Fenton reaction in cells to produce hydroxyl free radicals (·OH) and induce ferroptosis of tumor cells. In addition, MnO2 catalyzes the production of O2 from H2 O2 and enhances the production of singlet oxygen (1 O2 ) by IR783 under laser irradiation, thus increasing the production and accumulation of ROS to provide photodynamic therapy. The highly biocompatible IR783-Fe@MnO2 -HA nano-photosensitizers have exhibited tumor-targeting ability and efficient tumor inhibition in vivo due to the synergistic effect of photodynamic and ferroptosis antitumor therapies.

Modified surfatron device to improve microwave-plasma-assisted generation of RONS and methylene blue degradation in water

Microwave-induced plasmas generated at atmospheric pressure are very attractive for a great variety of applications since they have a relatively high electron density and can generate large amounts of reactive species. Argon plasmas can be sustained inside dielectric tubes but are radially contracted and exhibit filamentation effects when the diameter of the tube is not narrow enough (over 1.5 mm). In this work, we describe a new approach for creating microwave (2.45 GHz) plasmas under atmospheric pressure conditions by using a surfatron device and power from 10 W. This modified design of the reactor enables the sustenance of non-filamented argon plasmas. These new plasmas have a higher gas temperature and electron density than the plasma generated in the original surfatron configuration. The new design also allows for the maintenance of plasmas with relatively high proportions of water, resulting in the generation of larger quantities of excited hydroxyl radicals (·OH*). Thus, this novel configuration extends the applicability of microwave-induced plasmas by enabling operation under new conditions. Finally, the degradation of methylene blue (MB) in aqueous solutions has been assessed under different initial dye concentrations and argon flow conditions. The new plasma produces a substantial increase in hydrogen peroxide and nitrate concentrations in water and leads to a noteworthy enhancement in MB degradation efficiency. The introduction of water into the plasma produces a minor additional improvement.

Feasibility of atmospheric cold plasma for the elimination of food hazards: Recent advances and future trends

In recent decades, food safety has emerged as a worldwide public health issue with economic and political implications. Pesticide residues, mycotoxins, allergens, and antinutritional factors are the primary concerns associated with food products due to their potential adverse health effects. Although various conventional processing methods (such as washing, peeling, and cooking) have been used to reduce or eliminate these hazards from agricultural food materials, the results obtained are not quite satisfactory. Recently, atmospheric cold plasma (ACP), an emerging low -temperature and green processing technology, has shown great potential for mitigating food hazards. However, detailed descriptions of the effects of ACP treatment on food hazards are still not available. Thus, the current review aims to highlight recent studies on the efficacy and application of ACP in the reduction or elimination of pesticide residues, mycotoxins, allergens, and antinutritional factors in various food products. The possible working mechanisms of ACP and its effect on food quality, and the toxicity of degradation products are emphatically discussed. In addition, multiple factors affecting the efficacy of ACP are summarized in detail. At the same time, the major technical challenges for practical application and future development prospects of this emerging technology are also highlighted.

Efficient degradation and detoxification of methylene blue dye by a newly isolated ligninolytic enzyme producing bacterium Bacillus albus MW407057

In present work, a LiP enzyme producing bacterium was isolated form textile wastewater and sludge sample and identified as Bacillus albus by 16S rRNA gene sequencing analysis. This bacterium decolorized 99.27 % MB dye and removed 83.87 % COD within 6 h at 30 °C, pH 7, 100 rpm and 100 mg/l of dye concentration in presence of glucose and yeast extract as carbon and nitrogen source, respectively. The bacterium also produced LiP enzyme of molecular weight ∼48 kDa, characterized by SDS-PAGE analysis. Different metabolites like monomethylthionine, thionin, (E)-2-(3-Oxopropylidene)-2H-benzo[b][1,4] thiozine-3-carboxylic acid, N-(3,4-dihydroxyphenyl)-N-methylformamide, ethylamine, water and carbon dioxide produced during treatment process were characterized by FT-IR and LC-MS analysis. Further, the toxicity assessment results showed that the toxicity of bacteria treated dye solution was reduced significantly allowing 90 % seed germination indicating that the isolated bacterium B. albus has high potential to decolorize and detoxify MB dye for environmental safety.

Removal of Pharmaceutical Residues from Water and Wastewater Using Dielectric Barrier Discharge Methods-A Review

Persistent pharmaceutical pollutants (PPPs) have been identified as potential endocrine disruptors that mimic growth hormones when consumed at nanogram per litre to microgram per litre concentrations. Their occurrence in potable water remains a great threat to human health. Different conventional technologies developed for their removal from wastewater have failed to achieve complete mineralisation. Advanced oxidation technologies such as dielectric barrier discharges (DBDs) based on free radical mechanisms have been identified to completely decompose PPPs. Due to the existence of pharmaceuticals as mixtures in wastewater and the recalcitrance of their degradation intermediate by-products, no single advanced oxidation technology has been able to eliminate pharmaceutical xenobiotics. This review paper provides an update on the sources, occurrence, and types of pharmaceuticals in wastewater by emphasising different DBD configurations previously and currently utilised for pharmaceuticals degradation under different experimental conditions. The performance of the DBD geometries was evaluated considering various factors including treatment time, initial concentration, half-life time, degradation efficiency and the energy yield (G50) required to degrade half of the pollutant concentration. The review showed that the efficacy of the DBD systems on the removal of pharmaceutical compounds depends not only on these parameters but also on the nature/type of the pollutant.

Spin Coating Immobilisation of C-N-TiO2 Co-Doped Nano Catalyst on Glass and Application for Photocatalysis or as Electron Transporting Layer for Perovskite Solar Cells

Producing active thin films coated on supports resolves many issues of powder-based photo catalysis and energy harvesting. In this study, thin films of C-N-TiO2 were prepared by dynamic spin coating of C-N-TiO2 sol-gel on glass support. The effect of spin speed and sol gel precursor to solvent volume ratio on the film thickness was investigated. The C-N-TiO2-coated glass was annealed at 350 °C at a ramping rate of 10 °C/min with a holding time of 2 hours under a continuous flow of dry N2. The C-N-TiO2 films were characterised by profilometry analysis, light microscopy (LM), and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The outcomes of this study proved that a spin coating technique followed by an annealing process to stabilise the layer could be used for immobilisation of the photo catalyst on glass. The exposure of C-N-TiO2 films to UV radiation induced photocatalytic decolouration of orange II (O.II) dye. The prepared C-N-TiO2 films showed a reasonable power conversion efficiency average (PCE of 9%) with respect to the reference device (15%). The study offers a feasible route for the engineering of C-N-TiO2 films applicable to wastewater remediation processes and energy harvesting in solar cell technologies.