Dielectric Barrier Discharge System Research Articles

Power Calculation of Pulse Power-Driven DBD Plasma

A dielectric barrier discharge (DBD) in atmospheric pressure air was excited by a high-voltage pulse power supply. Capacitors with different capacitance were connected in the discharge circuit and their effects on discharge power calculation were evaluated. The average power deposited into the discharge were calculated by three different methods: 1) Lissajous figure; 2) product of voltage and current; and 3) watt-hour meter. Further studies showed that the capacitor with 10 nF was suitable for power calculation. At applied voltage of 9 kV, discharge power calculated by three methods were similar (around 25-27 W). However, with the increase of applied voltage, the discharge power obtained by product of voltage and current was far beyond the real value. Lissajous method has proven more appreciable for discharge power calculation in a pulsed plasma at high voltage. This study provides a practical guide for power calculation in a pulsed-driven DBD system.

Ozone Production in Cylindrical Co-axial Double Dielectric Barrier Discharge Ozone Generator

This study developed an ozone generator of a double co-axial cylindrical dielectric barrier discharge system with air, argon, and oxygen as the working gases. The discharge was produced by using a high voltage power supply of 0 - 18 kV and a line frequency of 50 Hz. The flow rate of air, argon, and oxygen was varied from 1 to 6 L/min. A comparison of O3 generation in air, argon, and oxygen using brass as a central electrode was conducted and it was found that O3 concentration was higher in the case of oxygen than in the air and in argon gases environment for given fixed discharge time, applied voltage, and diameter of the brass electrode. This study revealed that the concentration of ozone increased along with the increase in the applied voltage for constant discharge time and gas flow rate. The O3 concentration also increased with the increase in the discharge time at fixed applied voltage and gas flow rate; however, the concentration decreased with the increase in the gas flow rate at fixed discharge time, applied voltage, and diameter of the electrode. A small reactor with a large inner electrode generated a high concentration of O3. Yet, a reactor with a small diameter, there seemed to have an optimum inner electrode diameter. The glass tube reactor of the internal diameter of 18 mm and the brass electrode of diameter 8 mm were utilized in this study. The ozone concentration was higher for oxygen as feed gas than both in the air and in argon and the O3 concentration was also higher in the air than in argon at fixed discharge time, applied voltage, and diameter of ozone generator. HIGHLIGHTS Ozone concentration increases with increasing applied voltage and discharge time but concentration decreases with increasing gas flow rates Low cost ozone can be produced in DBD reactor at atmospheric pressure Oxygen can be used as feed gas to generate high concentration of ozone than other gases inside DBD generator Optimization of central electrode diameter and gap space inside DBD reactor can help to increase ozone concentration, yield, and efficiency Proper choice of central high voltage electrode also can play the important role for the generation of ozone in DBD chamber GRAPHICAL ABSTRACT

Research on quinoline degradation in drinking water by a large volume strong ionization dielectric barrier discharge reaction system

Quinoline is widely used in the production of drugs as a highly effective insecticide, and its derivatives can also be used to produce dyes. It has a teratogenic carcinogen to wildlife and humans once entering into the aquatic environment. In this study, the degradation mechanism of quinoline in drinking water by a strong ionization dielectric barrier discharge (DBD) low-temperature plasma with large volume was explored. High concentration of hydroxyl radical (·OH) (0.74 mmol l−1) and ozone (O3) (58.2 mg l−1) produced by strongly ionized discharge DBD system were quantitatively analyzed based on the results of electron spin resonance and O3 measurements. The influencing reaction conditions of input voltages, initial pH value, ·OH inhibitors, initial concentration and inorganic ions on the removal efficiency of quinoline were systematically studied. The obtained results showed that the removal efficiency and TOC removal of quinoline achieved 94.8% and 32.2%, degradation kinetic constant was 0.050 min−1 at 3.8 kV and in a neutral pH (7.2). The proposed pathways of quinoline were suggested based on identified intermediates as hydroxy pyridine, fumaric acid, oxalic acid, and other small molecular acids by high-performance liquid chromatography/tandem mass spectrometry analysis. Moreover, the toxicity analysis on the intermediates demonstrated that its acute toxicity, bioaccumulation factor and mutagenicity were reduced. The overall findings provided theoretical and experimental basis for the application of a high capacity strong ionization DBD water treatment system in the removal of quinoline from drinking water.

Fast and efficient removal of caffeine from water using dielectric barrier discharge

Caffeine is a well-known central nervous system stimulant, which can cause anxiety, insomnia and nervousness. Domestic wastes of caffeinated drinks, beverages and chocolates are the major sources for entry of caffeine in the environmental system. Caffeine has been widely detected in natural water resources. The current study describes a method for efficient removal of caffeine from aqueous solution by a laboratory scale dielectric barrier discharge (DBD) in open air. Caffeine concentrations in various sample solutions were monitored by high-performance liquid chromatography, and the degradation products were identified by directly injecting the sample to mass spectrometer. The consequences of varied parameters such as input power, initial concentration and initial pH of the solution on the degradation of caffeine were investigated. Removal efficiency of caffeine from aqueous solution was 72.6% and 96.6% for the initial concentrations of 100 and 1 µg/mL, respectively, at initial pH 7 after 4 min treatment in DBD plasma system with 60 W input powers. Caffeine removal efficiency was less in acidic solutions (initial pH 4), and insignificant degradation was observed in alkaline solutions (initial pH 10). Furthermore, the degradation of caffeine was also enhanced by increasing the input power in DBD system. The DBD system used in this study has been considered to be fast, effective and economical. It was operated at atmospheric condition in open air without using catalyst, expensive gases or organic solvents, and significant degradation of caffeine was achieved in a short (4 min) treatment time.

Hydrophilization of Polyester Textiles by Nonthermal Plasma

Abstract Polyester is a popular class of material used in material engineering. With its 0.4% moisture regain, polyethylene terephthalate (PET) is classified as highly hydrophobic, which originates from its lack of polar groups on its backbone. This study used a parallel-plate nonthermal plasma dielectric barrier discharge system operating at medium pressure in dry air and nitrogen (N2) to alter the surface properties of PET fabrics to increase their hydrophilic capabilities. Water contact angle, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were utilized to analyze any effect from the plasma treatment. The wettability analysis revealed a reduction in the contact angle of more than 80% within 5 min for both discharges. Scanning electron microscopy analysis showed no microscopic damage to the fiber structure, guaranteeing that the fabrics’ structural integrity was preserved after treatment. AFM analysis showed an increase in the nanometer roughness, which was considered beneficial because it increased the total surface area, further increasing the hydrophilic capacity. XPS analysis revealed a sharp increase in the presence of polar functional groups, indicating that the induced surface changes are mostly chemical in nature. Comparing that of untreated fabrics to treated fabrics, a Increase in water absorption capacity was observed for air-treated and N2-treated fabrics, when these fabrics were used immediately after plasma exposure.

Acceleration of the reaction of H2S and SO2 by non-thermal plasma to improve the mercury adsorption performance of activated carbon

Activated carbon (AC) loading sulfur can improve mercury adsorption performance. Fine sulfur clusters can be generated by the H2S and SO2 reaction, but the reaction is extremely slow at ambient temperatures. This study proposes a cost-effective and efficient method for non-thermal plasma (NTP) to accelerate the reactions between H2S and SO2 on AC to improve elemental mercury (Hg0) removal performance. The NTP treatment experiment was carried out on a laboratory-scale dielectric barrier discharge system. The Hg0 adsorption experiment was conducted via the Tekran Hg CEMS online monitoring device. The results showed that NTP treatment accelerated the reaction of H2S and SO2. The specific surface area and surface morphology of the AC had no significant changes after NTP treatment. However, the surface of AC was enriched with more sulfur in a very short time. H2S and SO2 presented an optimum mixing ratio of 2:1. NTP exhibited an optimum treatment time and voltage of 1 min and 3 kV, respectively. The Hg0 removal efficiency was increased by approximately 70% as compared to AC. In addition, the effects of the adsorption temperature and individual flue gas composition were explored. Further X-ray photoelectron spectroscopy analysis and temperature programmed desorption were also performed. Hg0 adsorption was mainly controlled by chemisorption, wherein the elemental sulfur loaded on AC was the main active site for Hg0 conversion to mercuric sulfide (HgS).

Decomposition of gaseous chlorobenzene using a DBD combined CuO/α-Fe2O3 catalysis system

ABSTRACT Copper oxide and hematite (CuO/α-Fe2O3) composite catalysts were prepared by using goethite as precursor adopted impregnation way and applied to the dielectric barrier discharge (DBD) catalytic decomposition of gaseous chlorobenzene. The CuO/α-Fe2O3 composite was characterised by X-ray diffraction, Brunauer–Emmett–Teller method, scanning electron microscopy and X-ray photoelectron spectrometer technique. The decomposition efficiency and energy yield of gaseous chlorobenzene in DBD catalysis system were studied by a function of gas flow rate, initial concentration and input voltage. The results showed that the CuO/α-Fe2O3 composite catalyst exhibited remarkable performance on chlorobenzene decomposition when the molar ratio was 0.4 and calcination temperature was 450°C. When the chlorobenzene initial concentration was 230 mg m−3, the chlorobenzene decomposition efficiency and mineralisation rate on the DBD catalysis system reached 73.33% and 63.37%, respectively, its decomposition and mineralisation efficiency were enhanced about 20.5% and 16.61%, respectively, compared with the bare DBD system, and it also benefited to significantly reduce the ozone and NO2 by-products. The possible pathway of chlorobenzene decomposition in the DBD catalytic hybrid system was proposed based on the products analysis.

Very large-scale gap distances of atmospheric pressure dielectric barrier glow discharge using semiconductor materials

Very large-scale gap distances of atmospheric pressure dielectric barrier discharge (DBD) in glow mode are obtained through semiconductor materials. The maximum value of the gap distance is up to 70 mm. Based on the feature of the cathode sheath, Auger neutralization theory, the trapped electron and the accumulated charge in the DBD system, the secondary electron emission is one of the primary reasons for very large-scale gap distances of the DBD to produce glow discharge. Furthermore, the contribution of the effective capacitance, the gas voltage and the discharge power are also discussed. Significant for the research are the development and the practical applications of atmospheric pressure glow discharge in the DBD with very large-scale gap distances.

Catalytic degradation of dinotefuran by dielectric barrier discharge plasma combined with La-doping TiO2

ABSTRACT Degradation of neonicotinoid insecticide dinotefuran (DIN) in dielectric barrier discharge (DBD) non-thermal plasma combined with lanthanum-doped titanium dioxide (La-TiO2) system was investigated. A La-TiO2 catalyst was prepared by the sol–gel method and characterized by SEM, XRD, and DRS. The effects of various factors (initial concentration, initial pH, input power, and addition of metal ions) on the removal rate of DIN were evaluated. The results indicated that when the initial concentration, input power, initial pH, and Fe2+ catalyst ions were 100 mg/L, 150 W, 10.5 and 50 mg/L, respectively, the DIN degradation efficiency was improved to 99.0% by coupling 10 wt% La-TiO2 at 180 min. La-TiO2 showed excellent catalytic performance on DIN degradation in a DBD system. The removal rate decreased with the presence of H2O2 and a scavenger, manifesting that plays an imperative role in the degradation process. Furthermore, intermediate products were analyzed by MS and the possible degradation pathway of DIN was proposed.

A medium-scale volume dielectric barrier discharge system for short-term treatment of cereal seeds indicates improved germination performance with long-term effects

Atmospheric pressure plasma has the potential of being applied in pre-harvest processes as a sustainable technology for seed and plant treatment. In this study, a medium-scale volume dielectric barrier discharge reactor with a power density of 53.5 mW/cm3 was developed and applied for continuous treatment of larger amount of seeds. Within the argon plasma, reactive oxygen and nitrogen species were observed by optical emission spectroscopy. Short-term plasma treatment in the range of seconds of wheat and barley seeds revealed improved germination performance accompanied by altered seed surface properties. Depending on the exposure time, plasma displayed a positive impact on maximum germination and germination speed in both species. In line with this, the t50 values were significantly decreased for plasma treated seeds compared to untreated seeds for wheat and barley. Cumulative germination was enhanced from 20% up to 53% after 27 h of germination for wheat seeds treated from 10 s to 60 s with plasma. Barley seeds respond to the short plasma treatment times with increased germination of 10%–23% after 24 h observation time. Moreover, the seed surface of both plant species became more hydrophilic after plasma treatment supported by a decrease in the water contact angle and an increase in hydrophilic functional groups being detected by x-ray photoelectron spectroscopy. Water uptake by seeds was moderately increased after 2 h of imbibition for both plant species. The positive effects of plasma treatment on germination performance were still detectable after storage of seeds for one and two months.

Resonance Properties of a Low-Pressure Dielectric Barrier Discharge

The electrical characteristics of a dielectric barrier discharge (DBD) symmetrical actuator at low pressures gave been investigated. A power source–actuator–DBD system has been analyzed. The plot of the feed voltage frequency at which a voltage resonance is observed at the outer electrodes of an actuator with a given configuration against air pressure has been constructed. The DBD density, as well as the capacitance and Q factor of the system, as a function of pressure in a pressure chamber, has been determined. It has been found that, as the pressure drops, the fraction of the DBD energy spent on generating a synthetic jet grows.

Ethylene Epoxidation in AC Dielectric Barrier Discharge Over Silver-Based Catalysts with Different Second Metals

This work was to investigate the effects of Ag-based catalysts and the addition of a second metal (Sn or Cu) loaded on an 0.1% wt% Ag catalyst on the ethylene epoxidation performance in a low-temperature and atmospheric pressure parallel plate dielectric barrier discharge (DBD) system with two frosted-glass plates and a separate N2O/C2H4 feed. The combined catalyst-DBD system with the 0.1 wt% Ag catalyst was found to provide significantly higher ethylene oxide (EO) selectivity, as compared to the sole DBD system, due to the additional surface reactions on the boundary area between the Ag active sites and silica support. The addition of the second metal (Sn or Cu) on the 0.1 wt% Ag catalyst substantially improved the EO selectivity, by reducing Ag particle sintering for Sn and increasing in the stability of oxometallacycle intermediates with high activation barriers for the formation of other products, causing an increased selectivity towards EO formation for Cu.

Temperature Stability and Effectiveness of Plasma-Activated Liquids over an 18 Months Period

Non-buffered plasma-activated liquids such as water and saline have shown bactericidal effects. In the present study, we investigated the anti-bacterial efficacy and stability of plasma-activated water (PAW) and plasma-activated saline (PAS), generated using a high voltage dielectric barrier discharge system. This study compares the potential of non-buffered plasma-activated liquids (PAL) for the inactivation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) after storage of the solutions at five different temperatures for a storage time up to 18 months after their generation. The temperatures used were room temperature, 4 °C, −16 °C, −80 °C, −150 °C. Both PAW and PAS achieved 6 log reduction for both bacteria on the first day of their generation after 60 min contact time and they retained these effects after 18 months when stored at the lowest temperatures. Chemical analysis of PAL showed that plasma caused a drop in pH, generation of reactive oxygen species and nitrates, whereas no nitrites are detected in the system used. The concentrations of chemical species were affected by the storage at different temperatures and a thermocouple probe was used to investigate the freezing behaviour of the PAL.

Numerical analysis on formation and transition of white-eye square superlattice patterns in dielectric barrier discharge system

The mechanism of formation and transformation of white-eye square patterns in dielectric barrier discharge system is investigated numerically, using the two-layer Lengyel–Epstein model with asymmetric and symmetric coupling. When the scale of the simulation system [Formula: see text] is two to three times of pattern wavelength [Formula: see text], it is found that an obvious intermediate state with square distribution appears by adjusting the ratio of diffusion coefficients [Formula: see text]/[Formula: see text]. When it is coupled with a suitable short-wavelength Turing mode in the range of [Formula: see text] to [Formula: see text], a new spatial resonance structure can be formed in the short-wavelength mode subsystem, and the pattern evolves from a simple square pattern to a white-eye square pattern. Although the two coupling methods achieve the same results, the duration time of the white-eye square pattern in the symmetric coupling method is significantly longer than that in the asymmetric coupling method. Because the quadratic coefficient of the amplitude equation in the reaction–diffusion system is not zero, the simple square pattern of the long wavelength mode subsystem gradually transits into a stable hexagon pattern gradually. As a result, the white-eye pattern transits from a square to a hexagon.

Preparation of CoFe2O4/MWNTs/sponge electrode to enhance dielectric barrier plasma discharge for degradation of phenylic pollutants and Cr(VI) reduction

CoFe2O4/MWNTs/sponge electrodes were prepared by co-adsorption of CoFe2O4 nanowires and multiwalled carbon nanotubes (MWNTs) onto a pure sponge, which were combined in a dielectric barrier discharge (DBD) plasma reactor to enhance discharge performance. The optimum concentration of CoFe2O4 nanowires contained in the CoFe2O4/MWNTs/sponge electrode was 0.5 g/L with a degradation rate of phenol of 98.52 % in 40 min. The CoFe2O4/MWNTs/sponge–DBD system significantly had the highest energy utilization efficiency with the tip discharge formed by CoFe2O4 nanowires and uniform discharge zone enlarged by modified sponge electrode. Further, phenol, hydroquinone, nitrobenzene, and p-nitrophenol as phenylic pollutants combined with hexavalent chromium (Cr(VI)) were treated simultaneously in CoFe2O4/MWNTs/sponge–DBD system. CoFe2O4 nanowires in DBD process formed photocatalytic and Fenton-like reaction could enhance phenylic pollutants degradation and Cr(VI) reduction. The synergistic removal effect between phenylic pollutants and Cr(VI) was discussed and the reaction mechanism in the CoFe2O4/MWNTs/sponge–DBD system was also explored.

Dielectric Barrier Discharge Systems with HV Generators and Discharge Chambers for Surface Treatment and Decontamination of Organic Products

The article presents applications of systems with power electronic converters, high voltage transformers, and discharge chambers used for nonthermal, dielectric barrier discharge plasma treatment of a plastic surface and decontamination of organic loose products. In these installations, the inductance of the high voltage transformers and the capacitances of the electrode sets form resonant circuits that are excited by inverters. The article presents characteristic features of the installations and basic mathematical relationships as well as the impact of individual parameters of system components. These converters with their output installations were designed, built, and tested by the authors. Some of the converters developed by the authors are manufactured and used in the industry.

Erratum: “Formation mechanism and application of a three-dimensional pattern in dielectric barrier discharge system” [Phys. Plasmas 27, 053503 (2020)

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Modification of powders by atmospheric pressure plasma and embedding into nickel coatings

The aim of this work was to achieve improved dispersibility of hydrophobic dry lubricants in aqueous media through plasma activation. As a result, the use of wet-chemical environmentally questionable substances – for example, certain surfactants – to ensure the dispersibility of such particles can be avoided. These plasma-activated particles can be further embedded in electroless nickel (Ni) coatings to improve wear behaviour. Thus, the hydrophobic polymeric powders polyimide and polyetheretherketone and the ceramic powder hexagonal boron nitride (BN) were activated with atmospheric pressure plasma using a diffuse coplanar dielectric barrier discharge system. The generation of polar chemical bonds on the powder surface resulted in an improved dispersibility of the powders in aqueous media. This led to a higher deposit volume of the particles in electroless nickel dispersion coatings. The modified bonding conditions at the powder surfaces were analysed with infrared and X-ray photoelectron spectroscopy. Optical microscopy and scanning electron microscopy investigations showed the deposit of the activated dispersed phase in the coatings. Furthermore, the wear behaviour of the coating was tested by using the Taber abraser test. The plasma activation led to surface modifications – namely, linkage of polar groups at the powder surfaces – and therefore to improved dispersibility. The deposition of the particles in the electroless nickel coatings was possible with all three materials, and the wear resistance of the coatings was improved.

A comparison of in- and post-plasma catalysis for toluene abatement through continuous and sequential processes in dielectric barrier discharge reactors

In the non-thermal plasma catalysis system, VOCs degradation was significantly affected by the position of the catalyst, as well as operation mode. Hence, it is of great significance to evaluate the performance of In Plasma Catalysis (IPC) and Post Plasma Catalysis (PPC) systems for VOCs abatement using both continuous and sequential processes. Four packed-bed dielectric barrier discharge (DBD) systems were used to degrade toluene with different catalysts under diverse voltages in this study. Results showed that the IPC mineralization rates were higher as compared to PPC, regardless of whether the continuous or sequential processes was used, and irrespective of the applied voltage and type of packed catalyst (e.g. 77.00% and 96.06% in SPPC and SIPC at 20 kV with Ag/ZSM-5 packed). However, PPC was superior to IPC in O3 and N2O reduction. As the applied voltage was raised, the mineralization rate in different reactors increased significantly, yet CO2 selectivity was insusceptible to voltage variation. NTP alone exhibited a mineralization rate and CO2 selectivity of 9.67%–22.62% and 53.85%–58.26%, respectively. While the mineralization rate and CO2 selectivity were remarkably improved with the presence of Ag/ZSM-5 (19.08%–41.59% and 93.99%–95.91% in CIPC). With respect to different catalysts investigated in this study, at 20 kV, Ag/ZSM-5 exhibited the highest mineralization rate - 96.06% in SIPC, and CO2 selectivity - 98.43% in SPPC; while the lowest concentrations of O3 (198 ppm) and N2O (8.01 ppm) were obtained in the Mn/ZSM-5 packed bed reactor. Possible reaction mechanisms were also proposed by analyzing the organic intermediates that were produced during continuous and sequential treatments, and remained in the adsorbents of IPC and PPC reactors.

Effects of cold plasma on wheat grain microbiome and antimicrobial efficacy against challenge pathogens and their resistance

The safety and quality of cereal grain supplies are adversely impacted by microbiological contamination, with novel interventions required to maximise whole grains safety and stability. The microbiological contaminants of wheat grains and the efficacy of Atmospheric Cold Plasma (ACP) for potential to control these risks were investigated. The evaluations were performed using a contained reactor dielectric barrier discharge (DBD) system; samples were treated for 0–20 min using direct and indirect plasma exposure. Amplicon-based metagenomic analysis using bacterial 16S rRNA gene and fungal 18S rRNA gene with internal transcribed spacer (ITS) region was performed to characterize the change in microbial community composition in response to ACP treatment. The antimicrobial efficacy of ACP against a range of bacterial and fungal contaminants of wheat, was assessed to include individual isolates from grains as challenge pathogens. ACP influenced wheat microbiome composition, with a higher microbial diversity as well as abundance found on the untreated control grain samples. Culture and genomic approaches revealed different trends for mycoflora detection and control. A challenge study demonstrated that using direct mode of plasma exposure with 20 min of treatment significantly reduced the concentration of all pathogens. Overall, reduction levels for B. atrophaeus vegetative cells were higher than for all fungal species tested, whereas B. atrophaeus spores were the most resistant to ACP among all microorganisms tested. Of note, repeating sub-lethal plasma treatment did not induce resistance to ACP in either B. atrophaeus or A. flavus spores. ACP process control could be tailored to address diverse microbiological risks for grain stability and safety.