Cylindrical Dielectric Barrier Discharge Research Articles

Degradation of dyes using reactive species of atmospheric pressure dielectric barrier discharge formed by a pencil plasma jet

The dye degradation efficacy of the cold plasma pencil jet is presented in the present investigation. Dye degradation studies were performed using air plasma, six different types of selected dyes (erythrosine, metanil yellow, sudan I, crystal violet, rhodamine B, and Indigo). The degradation of dyes is analyzed using UV visible spectroscopy, total organic carbon, and chemical oxygen demand. The results showed complete degradation of all types of dyes in UV visible analysis with minimum time for indigo (3 min) and maximum time for erythrosine (45 min). Moreover, erythrosine (k = 1.08 mg l−1 min−1), sudan I (k = 3.46 mg l−1 min−1), rhodamine B (k = 3.955 mg l−1 min−1), and Indigo (k = 18.915 mg l−1 min−1) follows approximate zeroth-order degradation kinetic, and metanil yellow (k = 0.094 min−1) and crystal violet (k = 0.25 min−1), closer to first-order degradation kinetics. Additionally, a substantial enhancement in mineralization and reduction in chemical oxygen demand of all the dyes occurs after plasma treatment. In this study, air plasma is produced in the cylindrical coaxial dielectric barrier discharge configuration. Electrical characterization of plasma is performed and the plasma species are identified using optical emission spectroscopy. The toxicity of plasma degraded dyes solutions toward freshwater algae species (Chlorella Sorokiniana and Chlorella Pyrenoidosa) are significantly low compared to virgin dyes solutions. The study reveals that pencil plasma jet substantially degrades dyes as well as converts the dyes solutions non-toxic.

Innovative carbon-nitrogen-TiO2 catalyst immobilised on stainless steel mesh for effective removal of orange II organic dye in the DCDBD plasma actuator

A double cylindrical dielectric barrier discharge (DCDBD) was optimised and coupled with SS/C-N-TiO2 photocatalysts produced by sol gel technique for the treatment of orange II (O.II) dye. The results show that degradation of 60 mg/L O.II with both systems followed first-order reaction. Higher removal of O.II was achieved with DCDBD-SS/C-N-TiO2 technology. The decomposition of O.II resulted in six and four degradation metabolites with DCDBD alone, and DCDBD-SS/C-N-TiO2, respectively. The COD and TOC removals reached 61.43% and 15.38%, respectively after 60 min of DCDBD run. This study demonstrates that DCDBD is a promising advanced technology for the treatment of dye wastewater.

Soot oxidation over V/ZSM-5 catalysts in a dielectric barrier discharge (DBD) reactor: Performance enhancement by transition metal (Mn, Co and Fe) doping

The oxidation of soot particles over a series of M-V/ZSM-5 (M = Mn, Co and Fe) catalysts was examined in a cylindrical dielectric barrier discharge (DBD) plasma reactor. Soot particles were completely removed in plasma reactor at 60th minute of reaction. The Mn-V/ZSM-5 catalyst showed higher catalytic activity of soot particles than Co-V/ZSM-5, Fe-V/ZSM-5 and VOx/ZSM-5 catalyst in the plasma reactor. However, the variation in CO2 selectivity was opposite to the change in soot oxidation rate. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS) and temperature programmed reduction of hydrogen (H2-TPR) were performed to gain insights of the relationships between catalyst properties and performance of plasma-catalytic soot oxidation. The results substantiated that the concentration of Oads had the most significant effect on the soot oxidation process, while the specific surface area of the M-V/ZSM-5 catalysts showed only minor influence. Moreover, the relative contents of oxygen and V5+ species of the M-V/ZSM-5 catalysts were also the major factors affecting soot oxidation. In addition, higher discharge power and oxygen content were conducive to accelerating soot oxidation. The stability tests showed that the Mn-V/ZSM-5 catalyst maintained good catalytic activity after three cycles of plasma-induced experiments.

Investigation of Fludioxonil Reduction Using Non-Thermal Atmospheric Plasma through Experimental Simulation

In this study, the effect of non-thermal atmospheric plasma (NTAP) treatment on the reduction of residual fludioxonil (C12H6F2N2O2, 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) was investigated through experimental simulation. Fludioxonil is known for its high residual concentration on fruits and vegetables. To simulate residual fludioxonil reduction in the storage location prior to consumption of fruits or vegetables by consumers, we designed an experimental setup utilizing a gas distribution system and a cylindrical dielectric barrier discharge (DBD) plasma source. A cylindrical DBD plasma source was adopted to produce the plasma activated chemical species (O3). To evaluate the effect of plasma treatment on the reduction of residual fludioxonil, experiments were performed under three different conditions: varying concentrations and treatment times of O3, as well as the surface roughness of microscope slide glass. Based on the results, 10 min plasma treatment with an O3 concentration of 11.89 μL/L, which showed a 58.5% reduction rate, is recommended. The O3 concentration has a higher priority than the treatment time for reduction rates of residual fludioxonil.

Degradation of methylene blue aqueous solution using atmospheric pressure dielectric barrier discharge

Methylene blue (MB) is toxic to humans and aquatic animals, and its removal from aqueous solutions requires high power consumption and long processing times. To improve the effect of dielectric barrier discharge (DBD) treatment of methylene blue and increase the energy utilization rate. In this study, we employed a novel approach, using a cylindrical DBD reactor, to treat MB in aqueous solutions. We found several factors, including input voltage, aqueous solution flow rate, number of high voltage electrodes, electrode size, and inside diameter of the dielectric tube influenced the MB removal rates with DBD. Our experimental results indicate that the change of electrode parameters can effectively improve the removal rate of methylene blue in DBD plasma treatment. At the same time, electrode parameters can lead to medium layer change of energy consumption; hence, the influence of electrode parameters on energy utilization efficiency also has an optimal value.

Design and Construction of a New Plasma Applicator for the Improved Disinfection and Activation of Large Surfaces

This paper describes the design and operation of a low-cost plasma applicator based on a patented, swirled-type dielectric barrier discharge configuration with a treatment width up to 300 mm. Differences from earlier plasma applicators include: blown cylindrical dielectric barrier discharge, combining the functional properties of the plasma jet systems, arc and corona discharge blown in a single type of universal applicator, and the possibility of treating large areas of samples with cold plasma generated in a certain type of specific process gas mixture chosen according to the type of desired effect. We tested the effect of the plasma on a few materials such as cotton and linen fabrics, glass wafers and printing cardboard, proving that the generated plasma can easily make hydrophilic or hydrophobic surfaces. We also tried the plasma’s sterilizing effect on Escherichia coli (E. coli) bacteria. The results suggest that our plasma system can be successfully applied to medical and biological fields as well, where the removal of bacteria and their fragments is required.

Analytical Model and Experimental Study of a Cylindrical DBD Discharge Operating in the Filamentary Mode

In this work, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz.

A novel double dielectric barrier discharge reactor for toluene abatement: Role of different discharge zones and reactive species

A coaxial cylindrical double dielectric barrier discharge (DDBD) reactor with two separate discharge zone was designed and the role of its different discharge zones and reactive species were explored in toluene degradation. The inner tube (the space between the high voltage electrode and the inner barrier) had a higher gas temperature and reactive species concentration due to its stronger discharge intensity compared with the outer tube (the space between the inner and outer barriers). The two discharge zones exhibited similar toluene removal efficiency, whereas the mineralization rate of the inner tube exceeded that of the outer tube under 18–22 kV, and the result was opposite under 24–28 kV. The gas-flow direction had no significant effect on the toluene removal efficiency, but the mineralization rate of the down-flow reactor (23.7%–54.4%) exceeded that of the reverse-flow reactor (20.7%–45.5%). The inner and outer tubes mainly responsible for the initial degradation and further oxidation of toluene, respectively. The role of long-lived (N2(A3∑u+) and metastable O2 (a1Δg and b1Σg+)) and short-lived (N2(C3∏u), N2(B3∏g), and atomic O (1D and 3P)) reactive species on toluene degradation and oxidation was analyzed. The plausible toluene degradation mechanism in the DDBD reactor was proposed based on the role of different discharge zones and reactive species. The finding herein is significant in the design, optimization and application of DBD reactors.

Plasma-enhanced catalytic oxidation of ethylene oxide over Fe–Mn based ternary catalysts

In this work, Fe–Mn based ternary catalysts (Fe–Mn-X, X = Ce, Co and Cu) were evaluated in the plasma-catalytic oxidation of ethylene oxide (EO) using a cylindrical dielectric barrier discharge (DBD) reactor. The addition of transition metal dopants to the Fe–Mn catalyst significantly improved the performance of plasma-catalyzed EO oxidation compared to the reaction using plasma only and the Fe–Mn catalyst. The highest EO conversion (91.9%) and CO2 selectivity (78.9%) were obtained over the Fe–Mn–Co catalyst at a specific energy input (SEI) of 730.2 J l−1. Moreover, the presence of water vapor improved EO conversion and CO2 selectivity in the relative humidity (RH) range of 0–60%, while further increasing the RH to 80% reduced EO conversion. The interactions between Fe, Mn and dopants increased the specific surface area and pore volume of the Fe–Mn-X catalyst, while maintaining the crystalline structure of the catalysts. The presence of the dopants enhanced the reducibility of the Fe–Mn-X catalysts and produced more surface adsorbed oxygen (Oads) on the catalyst surfaces. Moreover, the interactive effects among the Fe, Mn and dopants facilitated the plasma-catalytic oxidation reactions via enhanced surface reactions. The coupling of plasma with the Fe–Mn–Co catalyst reduced the formation of organic by-products in the plasma-catalyzed oxidation of EO.

P-Nitrophenol contaminated soil remediation in a spray-type coaxial cylindrical dielectric barrier discharge plasma system.

In the present work, plasma remediation of p-nitrophenol (PNP) contaminated soil was performed in a novel spray-type coaxial cylindrical dielectric barrier discharge (DBD) system at ambient temperature. This system is capable of generating large-size nonthermal plasma (NTP) and improving the diffusion and transfer of chemical active species around the dispersed soil particles. Several key parameters including plasma treatment time, discharge voltage, soil granular size, the entry speed of soil, PNP initial concentration, gas variety, and gas flow rate were investigated in terms of PNP degradation and energy efficiencies. Under the optimized experimental conditions, 54.2% of PNP was degraded after only 50 s discharge treatment, indicating that the spray-type coaxial cylindrical DBD system can degrade organic pollutants in soil more quickly compared to other plasma systems due to its efficient transfer of reactive oxygen and nitrogen species (RONS) into the contaminated soil. The possible PNP degradation pathways were proposed based on intermediates identification results and the role of reactive species analysis. The toxicological assessment of the PNP decomposition products was conducted by quantitative structure-activity relationship (QASR) analysis. This work is expected to provide a potential plasma technology for rapid and efficient processing of industrial organic pollutants contamination soil.

Comparative Study and Experimental Optimization of Ozone Generators by Cylindrical Surface Dielectric Barrier Discharge (DBD)

The dielectric barrier discharge (DBD) is a more efficient medium of ozone production, which requires voltages of the order of several kV and frequencies of a few tens of kHz. The principal objective of this study is to model and optimize a cylindrical-shaped ozone generator with a surface DBD that will be used in a water treatment plant. By playing on the electrical parameters (voltage, oxygen flow) and geometric parameters (the nature and diameter of the dielectric, the length of the electrode), to achieve high ozone efficiency and minimum energy consumption. It is recommended to use cylindrical surface discharge reactors with reduced diameter and electrode length and with the smallest possible oxygen circulation interval to achieve satisfactory ozone concentrations, with reduced power consumption.

Degradation of Sulfamethoxazole by Double Cylindrical Dielectric Barrier Discharge System combined with Ti /C-N-TiO2 supported Nanocatalyst

The presence and detection of persistent pharmaceutical pollutants (PPPs) in aquatic environments requires urgent remediation. C-N-TiO2 was prepared by sol-gel method and immobilised on Ti mesh by dip-coating technique followed by pyrolysis in the furnace at 350°C for 105 minutes. The Ti/C-N-TiO2 photocatalyst were characterised by SEM, EDS, XRD, Raman spectroscopy, and XPS. An optimised DCDBD system alone or combined with Ti/C-N-TiO2 catalysts were compared for the degradation of sulfamethoxazole (SMX) simulated wastewater at the applied conditions. The SEM-EDS results showed that C, N, and Ti were all present in the C-N-TiO2 nano catalyst layer supported upon Ti mesh. XPS results revealed existence of Ti in +4 oxidation states despite the addition carbon and nitrogen. The XRD and Raman patterns confirmed the formation of anatase as dominant phase. The antibacterial tests of Ti/C-N-TiO2 films showed an excellent effect on E. coli inhibition. The degradation of SMX with DCDBD and DCDBD/C-N-TiO2/Ti-mesh systems followed first-order reaction and complete mineralisation of the pollutants was achieved after 30 and 60 min of plasma run at rate constants of 3.79×10−2 min−1 (R2 = 0.999) and 2.18×10−2 min−1 (R2 = 0.997), respectively. The energy yield G50 required for the degradation of 50% SMX reached 34.64 g/kWh corresponding to an electrical efficiency per order (EE/O) of 40.527 kWh/m3 order1 with DCDBD alone within 18 min, and 19.787 g/kWh with DCDBD/Ti/C-N-TiO2 system corresponding to an EE/O of 70.458 kWh/m3 order1 after 32 min. Different recalcitrant degradation intermediate by-products were detected by HPLC/MS and their degradation pathways proposed. Therefore, this study offers a novel advanced oxidation technology for the remediation of SMX from aqueous solution.

Effect of megapore particles packing on dielectric barrier discharge, O3 generation and benzene degradation

Recently, packed-bed discharge plasma technologies have been widely studied for treatment of volatile organic compounds (VOCs), due to the good performance in improving the degradation and mineralization of VOCs. In this paper, a coaxial cylindrical dielectric barrier discharge reactor packed with porous material of micron-sized pores was used for degradation of benzene, and the discharge characteristics and ozone generation characteristics were studied. When the discharge length was 12 cm and the filling length was 5 cm, the packed particles in the discharge area significantly increased the number of micro-discharges, and the current amplitude and density increased with the pore size of packed particles, but the discharge power and ozone concentration showed a trend of first increasing and then decreasing. The discharge power and ozone production reached the maximum when the size of pore former was 75 μm, correspondingly, the degradation efficiency of benzene was the highest.

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

Effect of voltage and oxygen on inactivation of E. coli and S. typhi using pulsed dielectric barrier discharge

This work presents the study of the voltage and oxygen effect on bacterial inactivation in water using a pulsed dielectric barrier discharge (DBD) under atmospheric pressure, where Escherichia coli (E. coli) and Salmonella typhi (S. typhi) bacteria were used as model microorganisms. A cylindrical DBD reactor was developed and tested in applications to assay the efficiency of bacterial inactivation in water on a volume of 500 mL flowing continuously throughout the system assisted with a peristaltic pump at 4.4 ± 0.1 mL/s. The efficiency of the treatment reached a 6-log10 reduction for both E. coli and S. typhi bacteria at 106 CFU/mL of concentration at the end of the first cycle of treatment at a minimum voltage of 12 kV with oxygen bubbling gas, concluding that there was a minimum voltage to produce inactivation of E. coli and S. typhi samples. Bacterial inactivation without the oxygen condition contrasted with the high rate of inactivation with oxygen at relatively low voltage discharges.

Synergistic effect of catalyst and plasma on CO2 decomposition in a dielectric barrier discharge plasma reactor

Plasma has been widely used in wastewater treatment, material modification and biomedicine due to its unique properties. In this work, a coaxial cylindrical dielectric barrier discharge (DBD) reactor was set up to investigate the effects of electrode materials and catalyst combined with DBD plasma on CO2 decomposition under room temperature and atmosphere pressure. The materials of inner electrode and outer electrode were investigated without catalysts packed in the reactor. It was found that the aluminum rod as inner electrode performed better than copper rod and stainless steel rod due to the moderate thermal conductivity and electrical conductivity of aluminum rod. Nevertheless, copper foil worked better as external electrode material since its higher electrical conductivity facilitated generation of high energy electrons by the high voltage between electrodes. After perovskite-type catalyst was introduced in the reactor, CO2 conversion increased, which was attributed to the synergistic effect of perovskite combined with plasma discharge. Perovskite-type catalysts could modulate the capacitance of the reactor to make plasma discharge more uniform and increased CO2 conversion, while plasma discharge provided high energy electrons that activated oxides sites and basic sites of perovskite-type catalysts. The maximum CO2 conversion was 23 % and maximum energy efficiency was 2.1 % when MgTiO3 was packed in the reactor.

Integrated gasification and non-thermal plasma-catalysis system for cleaner syngas production from cellulose

An innovative integrated gasification and plasma-catalytic system has been developed to produce cleaner syngas from a model biofeedstock (α-cellulose). The influence of Co/γ-Al2O3 catalyst on the plasma reforming of tar-contaminated syngas has been investigated using a cylindrical dielectric barrier discharge reactor. The results show that plasma-catalytic processing of the syngas from biomass gasification significantly reduces the concentration of tars by 88% and enhances the total gas product yield and the syngas ratio (H2/CO) by up to 90%.

An Experimental Study of Co-Axial Dielectric Barrier Discharge for Ozone Generation

In this research work, co-axial cylindrical dielectric barrier discharge (CCDBD) system has been used as a ozone generator for ozone production with air as a working gas. The breakdown of air was generated inside the reactor by using low line frequency of 50 Hz and high AC voltage power supply system. The variation of air flow rate (Q) was taken from 10 to 16 l/min in this experiment. The O3 concentration denoted by C(O3) decreases with increasing the rate of flow of air at fixed discharge time and applied voltage. When discharge time (t) increases, C(O3) increases at fixed applied voltage. C(O3) also increases with increasing applied voltage (V) for constant discharge time. If the gap space between the electrodes increases then C(O3) increases. We have used glass tube reactor for this work having internal diameter of 18 mm and copper, brass and iron electrodes of diameter 8 mm. It was estimated that C(O3) found higher for copper electrode than both brass and iron electrode for certain discharge time, applied voltage and reactor diameter.

Spectroscopic Measurements of Dissolved O3, H2O2 and OH Radicals in Double Cylindrical Dielectric Barrier Discharge Technology: Treatment of Methylene Blue Dye Simulated Wastewater

Advanced oxidation technologies (AOTs) focusing on nonthermal plasma induced by dielectric barrier discharge are adequate sources of diverse reactive oxygen species (ROS) beneficial for water and wastewater treatment. In this study, indigo, peroxytitanyl sulphate and terephthalic acid methods were used to approximate the concentrations of O3, H2O2 and OH produced in a double cylindrical dielectric barrier discharge (DCDBD) plasma configuration. The effect of pH and scavengers as well as the amount of chemical probes on the generation of oxidants was investigated. The efficiency of the DCDBD reactor was further evaluated using methylene blue (MB) as model pollutant. The results demonstrated that the formation of oxidants O3, H2O2 and OH in the DCDBD reactor was pH-dependent. Furthermore, the presence of scavengers such as phosphates, bicarbonates and carbonates in the solution diminished the amount of OH in the system and hence could impact upon the degree of detoxification of targeted pollutants during water and wastewater treatment. The MB simulated dye was totally decomposed into H2O, dissolved CO2 and simpler aqueous entities. Herein the DCDBD design is an adequate AOT that can be used worldwide for effective decontamination of water and wastewater.

Relation between circuit current and plasma current density in plasma discharges with dielectric media

The theoretical derivation of the relation between moving charges in the plasma and external circuit current was first established on a firm basis by Sato [J. Phys. D 13, L3 (1980)] for the case of a discharge with constant applied voltage between bare electrodes. The generalization to time varying applied voltages was established by Morrow and Sato [J. Phys. D 32, L20 (1999)], still considering bare electrodes. In the present work, we extend the latter derivation to include general devices with arbitrarily arranged linear dielectric media, and multiple electrodes with time dependent voltages, of interest, for instance, for a Dielectric Barrier Discharge (DBD). In particular, the present derivation determines a general, practical expression for the reactive term present in the Morrow and Sato formula. Using the expression derived, we show how in simple DBD geometries usual circuit approximations of the plasma discharge can be obtained and its validity was justified. Also, we consider the determination of the internal plasma current from the measurement of the external circuit current for a cylindrical DBD operated with helium at atmospheric pressure. Finally, we apply the theory to a three-electrode device in order to relate electric measurements to volume integrals on the plasma that were shown to be useful in order to quantify species production by electron impact.