OH Emission Intensity Research Articles

Comparison between the water activation effects by pulsed and sinusoidal helium plasma jets

Comparisons between pulsed and sinusoidal plasma jets have been extensively reported for the discharge characteristics and gaseous reactive species, but rarely for the aqueous reactive species in water solutions treated by the two types of plasma jets. This motivates us to compare the concentrations of aqueous reactive species induced by a pulsed and a sinusoidal plasma jet, since it is widely reported that these aqueous reactive species play a crucial role in various plasma biomedical applications. Experimental results show that the aqueous H2O2, OH/O2−, and O2−/ONOO− induced by the pulsed plasma jet have higher concentrations, and the proportional difference increases with the discharge power. However, the emission intensities of OH(A) and O(3p5P) are higher for the sinusoidal plasma jet, which may be attributed to its higher gas temperature since more water vapor could participate in the plasma. In addition, the efficiency of bacterial inactivation induced by the pulsed plasma jet is higher than that for the sinusoidal plasma jet, in accordance with the concentration relation of aqueous reactive species for the two types of plasma jets.

A diffuse plasma jet generated from the preexisting discharge filament at atmospheric pressure

A diffuse plasma jet was realized by expanding the preexisting argon filamentary discharge into a diffuse one at atmospheric pressure. Examination of emission spectra from the plasma jet shows that the emission intensities of OH and Ar increase with the argon flow near the quartz tube nozzle, while the N2 emission intensity first increases, then decreases, and finally approximately remains unchanged with the increase in the argon flow of interest. It is also found that with the argon flow set at 0.4 l/min, most of the reactive species are gathered close to the nozzle, the OH and Ar emission intensities decrease quickly after the plasma propagates out of the nozzle, but the N2 emission is able to propagate over a larger distance. These distinct spectral emission features of OH, N2, and Ar are attributed to the different generation and quenching mechanisms of their corresponding excited states, i.e., OH(A Σ2 +), N2(C Π3 μ), and Ar(4p)/Ar(4s) in the argon plasma jet. Additionally, the formation of the diffuse plasma jet has been clarified by observing the discharge burning phase and solving the Poisson equation for the electric field distribution in an argon cylindrical dielectric-barrier discharge. The filamentary discharge deposits charged particles onto the dielectric. The positive surface charges in the positive half cycle induce a relatively high field in the local region close to the dielectric. The relatively high field and the high pre-ionization in this local region play a key role in initiating the diffuse positive corona.

Streamer Branching and Spectroscopic Characteristics of Surface Discharge on Water Under Different Pulsed Voltages

Complexity of branching pattern and OH production of water surface discharges was investigated by comparing nanosecond water surface discharge (NWSD) and microsecond water surface discharges (MWSDs) that were defined as NWSD and MWSD, respectively. Experimental and analyzed results between NWSD and MWSD under comparable maximum discharge length $l_{d}$ are summarized as follows: 1) NWSD showed the greatest complexity of branching pattern by fractal analysis; 2) electron density of NWSD was approximately two times greater than MWSD and both orders were 10−17 cm−3; 3) emission intensity of OH (A-X) from MWSD was greater than NWSD; 4) rotational temperature of NWSD was almost constant around 1000 K irrespective of $l_{d}$ and rotational temperature of MWSD increased with increasing $l_{d}$ ranging from 2000 to 4000 K. It was found that the complexity of discharge pattern on water may be affected by the field intensity at water/air boundary. OH production was presumed to be caused by thermal dissociation in this experimental condition.

INVESTIGATIONS OF VOLUME-CENTERED DISCHARGE IN AIR SUPERSONIC FLOW WITH ADDITIONAL PROPANE AND OXYGEN INJECTION

The flow arising in a volume-centered non-equilibrium discharge channel with propane and oxygen jet injection through an anode into supersonic airflow was investigated by the emission spectroscopy method. The experiments were carried out at M = 2, static pressure values of ~ 2.9 × 104 Pa (217 Torr) and 5.33 × 104 Pa (400 Torr), and discharge current in the range from 1 to ~ 1.85 A. Data on the composition and spatial distribution of the emission intensity of the reaction products, which appeared in the transformation process of the air–fuel mixture in the discharge region, were obtained. In particular, data on the CN, OH, and C2 emission intensity distributions and those for atomic hydrogen and oxygen are presented. The performed investigations allowed answering the question about the influence of the type of injecting components, methods of injection, and current values on the plasma chemical reaction intensities.

The OES Diagnosis in Removal of HCHO by the Uniform Bipolar Nanosecond-Pulsed DBD Using Wire-Cylinder Electrode Configuration in Atmospheric N2

In this paper, the uniform bipolar nanosecondpulsed dielectric barrier discharge (NPDBD) with 15-ns rising time generating in a wire-cylinder reactor is employed to remove the gaseous formaldehyde in atmospheric pressure N 2 . The image, the waveforms of pulse voltage and discharge current, the optical emission spectra of the discharges, and the removal rate of formaldehyde are recorded and calculated, respectively. It is found that the emission intensity of OH (A 2 Σ → X 2 Π, 0-0) rises when increasing the input power density (PD). Furthermore, with the increase of input PD and the emission intensity of OH (A 2 Σ → X 2 Π, 0-0), the removal rate of formaldehyde rises correspondingly. The results also indicate that when the O 2 concentration rises within 0%-5%, the removal rate of formaldehyde increases, however, when the O 2 concentration rises within 5%-20%, the formaldehyde removal rate decreases correspondingly. In addition, at the same conditions, the DBD synergistically removing formaldehyde with Al 2 O 3 and TiO 2 could increase the removal rate by 10%-30% compared with the discharge only.

Electronic ground state OH(X) radical in a low-temperature atmospheric pressure plasma jet

The wide applicability of atmospheric pressure plasma jets in biomedicine stems from the presence of reactive nitrogen and oxygen species generated in these plasma jets. Knowing the absolute concentration of these reactive species is of utmost importance as it is critical, along with the particle flux obtained from the plasma feed gas flow rate to ensure that the correct dosage is applied during applications. In this study, we investigate and report the ground state OH(X) number density acquired using cavity ringdown spectroscopy, along the propagation axis (z-axis) of a cold atmospheric pressure helium plasma plume. The jet was generated by a repetitively pulsed mono-polar square wave of duration 1 μs running at a frequency of 9.9 kHz. The voltage supplied was 6.5 kV with the helium flow rate fixed at 3.6 standard liters per minute. The rotational and vibrational temperatures are simulated from the second positive system of nitrogen, N2(C3πu−B3πg), with the rotational temperature being spatially constant at 300 K along the propagation axis of the atmospheric pressure plasma jet while the vibrational temperature is 3620 K at the beginning of the plume and is observed to decrease downstream. The OH(A) emission intensity obtained via optical emission spectroscopy was observed to decrease downstream of the plasma jet. The OH(X) number density along the propagation axis was initially 2.2 × 1013 molecules cm−3 before increasing to a peak value of 2.4 × 1013 molecules cm−3, from which the number density was observed to decrease to 2.2 × 1013 molecules cm−3 downstream of the plasma jet. The total OH(A, X) in the plasma jet remained relatively constant along the propagation axis of the plasma jet before falling off at the tip of the jet. The increase in vibrational temperature downstream and the simultaneous measurements of both the excited state OH(A) and the ground state OH(X) reported in this study provide insights into the formation and consumption of this reactive oxygen species while also providing a reference for determining the radical number density dosage for future cold plasma irradiation studies.

Transient change in the shape of premixed burner flame with the superposition of pulsed dielectric barrier discharge

We investigated the transient phenomena in a premixed burner flame with the superposition of a pulsed dielectric barrier discharge (DBD). The length of the flame was shortened by the superposition of DBD, indicating the activation of combustion chemical reactions with the help of the plasma. In addition, we observed the modulation of the top position of the unburned gas region and the formations of local minimums in the axial distribution of the optical emission intensity of OH. These experimental results reveal the oscillation of the rates of combustion chemical reactions as a response to the activation by pulsed DBD. The cycle of the oscillation was 0.18–0.2 ms, which could be understood as the eigenfrequency of the plasma-assisted combustion reaction system.

Kinetic analysis of acid orange 7 degradation by pulsed discharge plasma combined with activated carbon and the synergistic mechanism exploration

The synergistic technique of pulsed discharge plasma (PDP) and activated carbon (AC) was built to investigate the kinetics of acid orange 7 (AO7) degradation under different conditions of AC addition, electrode gap, initial pH value of solution, gas variety and gas flow rate. Emission spectra of OH and O, UV–vis absorption spectra of the AO7 solution and TOC removal were measured to illustrate the synergistic mechanism of the PDP and the AC. The obtained results indicated that the kinetic constant of AO7 degradation increased from 0.00947 min−1 to 0.01419 min−1 when 4 g AC was added into the PDP system; AO7 degradation was higher in the case of alkaline solution when oxygen was used as the flow gas in the PDP/AC system, 2 L/min oxygen flow was more favorable for the degradation. Results of the relative emission intensities of OH and O indicated the catalytic effect of the AC on the active species formation as well as the important role of the two radicals for the AO7 degradation. There was no new peaks appeared by the UV–vis analysis of the AO7 solution after 60 min treatment. The highest TOC removal in the PDP/AC system was 30.3%, which was achieved under the condition of 4 L/min air flow rate and 3 initial pH value.

Effect of cyclone Nilofar on mesospheric wave dynamics as inferred from optical nightglow observations from Mount Abu, India

AbstractMesospheric nightglow intensities at three emissions (O2(0–1), OH(6–2) bands, and Na(589.3 nm)) from a low‐latitude location, Gurushikhar, Mount Abu (24.6°N, 72.8°E), in India, showed similar wave features on 26 October 2014 with a common periodicity of around 4 h. A convective activity due to the cyclone Nilofar, which had developed in the Arabian Sea during 25–31 October 2014, was found to be the source as this too showed a gravity wave period coherent with that of the mesospheric emissions on the 26th. The periodicities at the source region were obtained using outgoing longwave radiation fluxes (derived from Kalpana‐1 satellite) which were used as a tracer of tropospheric activity. Cyclone Nilofar had two centers located at a distance of 1103 and 1665 km from the observational station. From the phase offset in time between residuals of O2 and OH emission intensities and the observed common periodicity the vertical phase speed and wavelength have been found to be 1.13 ms−1 and 16.47 km. From the wavelet analyses it is seen that the travel time of the wave from the convection region to O2 emission height was around 8.1 h. From these observations the horizontal phase speed and wavelength of the wave in the mesosphere were calculated to be 37.8 ms−1 and 553 km. These results thus provide not only unambiguous evidence on the vertical coupling of atmospheres engendered by the tropical cyclone Nilofar but also the characteristics of waves that exist during such cyclonic events.

Experimental investigation of atomization and combustion characteristics of high-pressure pulse sprays

This study investigated the effect of fuel injection pressure (20–80MPa) on atomization and combustion characteristics using a stationary combustor with an intermittent supply of liquid fuel. In the atomization experiments, spray tip penetration and spray width increased, and the Sauter mean diameter of droplets decreased with an increase in the fuel injection pressure. In the combustion experiments, the OH emission intensity and combustion gas temperature upstream of the furnace increased with the fuel injection pressure, whereas nitrogen oxides emissions were reduced. The results demonstrate that high-pressure pulse spray combustion can reduce NOX emissions and enhance the combustion load by an increase in the fuel injection pressure.

Spectroscopic and electrical characters of SBD plasma excited by bipolar nanosecond pulse in atmospheric air

In this paper, an atmospheric surface barrier discharge (SBD) generated by annular electrodes in quartz tube is presented through employing bipolar nanosecond pulse voltage in air. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra emitted from the discharges are recorded and calculated. A spectra simulation method is developed to separate the overlap of the secondary diffraction spectra which are produced by grating in monochromator, and N2 (B3Πg→A3Σu+) and O (3p5P→3s5S2o) are extracted. The effects of pulse voltage and discharge power on the emission intensities of OH (A2Σ+→X2Пi), N2+ (B2Σu+→X2Σg+), N2 (C3Πu→B3Πg), N2 (B3Πg→A3Σu+), and O (3p5P→3s5S2o) are investigated. It is found that increasing the pulse peak voltage can lead to an easier formation of N2+ (B2Σu+) than that of N2 (C3Πu). Additionally, vibrational and rotational temperatures of the plasma are determined by comparing the experimental and simulated spectra of N2+ (B2Σu+→X2Σg+), and the results show that the vibrational and rotational temperatures are 3250±20K and 350±5K under the pulse peak voltage of 28kV, respectively.

Origin of activated combustion in steady-state premixed burner flame with superposition of dielectric barrier discharge

The objective of this work is to understand the mechanism of plasma-assisted combustion in a steady-state premixed burner flame. We examined the spatiotemporal variation of the density of atomic oxygen in a premixed burner flame with the superposition of dielectric barrier discharge (DBD). We also measured the spatiotemporal variations of the optical emission intensities of Ar and OH. The experimental results reveal that atomic oxygen produced in the preheating zone by electron impact plays a key role in the activation of combustion reactions. This understanding is consistent with that described in our previous paper indicating that the production of “cold OH(A2Σ+)” via CHO + O → OH(A2Σ+) + CO has the sensitive response to the pulsed current of DBD [K. Zaima and K. Sasaki, Jpn. J. Appl. Phys. 53, 110309 (2014)].

A diffuse plasma generated by bipolar nanosecond pulsed dielectric barrier discharge in nitrogen

In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3Πu → B3 Πg, 0-2) and the first negative bands of N2 + (B2 Σu + → X2 Σg +, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH (A 2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH(A2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3Πu → B3Πg, 0-0, 337.1 nm) and OH (A2Σ → X2Π, 0-0) are more greater than that on the emission intensity of N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm).

Effect of voltage polarity on oxidation-reduction potential by plasma in water

Use of plasma in water for water treatment and medical treatment is growing and raises expectations of finding advanced functions such as an increase of biological compatibility. In the present study with a focus on the variation of oxidation-reduction potential (ORP), relationships between the electrode polarities of plasma in water and the change of water quality such as conductivity, H2O2 concentration, dissolved hydrogen concentration, pH and ORP were revealed. Similar line spectra of radiation at the electrode tip were observed for each case of positive and negative electrode polarity. The emission intensities of OH (309 nm), Hα (656 nm), and OI (777 nm) for the positive discharge were significantly higher than those for the negative one, though the energy consumption during the discharge period of both cases was nearly the same. Positive electrode polarity was found to be more suitable than negative electrode polarity for increasing dissolved hydrogen gas and hydrogen peroxide. The ORP for the positive polarity decreased from 460 to 45 mV and that for the negative polarity decreased from 460 to 183 mV, although the pH and conductivity were not significantly changed.

Surface Modification of Poly-ε-Caprolactone with an Atmospheric Pressure Plasma Jet

In this work, poly-e-caprolactone samples are modified by an atmospheric pressure plasma jet in pure argon and argon/water vapour mixtures. In a first part of the paper, the chemical species present in the plasma jet are identified by optical emission spectroscopy and it was found that plasmas generated in argon/0.05 % water vapour mixtures show the highest emission intensity of OH (A–X) at 308 nm. In a subsequent section, plasma jet surface treatments in argon and argon/water vapour mixtures have been investigated using contact angle measurements and X-ray photoelectron spectroscopy. The polymer samples modified with the plasma jet show a significant decrease in water contact angle due to the incorporation of oxygen-containing groups, such as C–O, C=O and O–C=O. The most efficient oxygen inclusion was however found when 0.05 % of water vapour is added to the argon feeding gas, which correlates with the highest intensity of OH (X) radicals. By optimizing the OH (X) radical yield in the plasma jet, the highest polymer modification efficiency can thus be obtained.

Atmospheric-Pressure Diffuse Dielectric-Barrier-Discharge Plasma Generated by Bipolar Nanosecond Pulse in Nitrogen and Air

A bipolar high-voltage pulse with 20-ns rising time is employed to generate diffuse dielectric-barrier-discharge plasma with very low gas temperature in both nitrogen and air using a wire-plate electrode configuration at atmospheric pressure. Both the diffuse nanosecond pulsed discharge images and the optical emission spectra are recorded successfully. The gas temperatures of the nitrogen and air discharge plasmas are determined at 400 ± 5 K and 320 ± 5 K. The effects of discharge gap distance, pulse peak voltage, and pulse repetition rate on the emission intensities of NO ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ→ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Π), OH ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ→ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Π, 0 - 0) , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> → <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) , and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> → <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , 0 - 0, 391.4 nm) in both nitrogen and air are investigated, respectively. The effects of O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and Ar on discharge images and the emission intensities in nitrogen are obtained. It is found that the emission intensities rise with increasing pulse peak voltage, pulse repetition rate, and the concentration of argon but decrease with increasing the discharge gap distance and the concentration of oxygen. The main physicochemical processes involved are discussed.

Absolute OH density measurements by broadband UV absorption in diffuse atmospheric-pressure He–H2O RF glow discharges

The measurement of radical densities in atmospheric-pressure plasmas has gained increasing importance in recent years in view of their crucial role in many applications. In this paper we present absolute OH density measurements by broadband UV absorption in diffuse atmospheric-pressure RF glow discharges in mixtures of He and H2O. The use of a 310 nm light-emitting diode as a light source and a very high resolution spectrometer (2.6 pm resolution) made the estimation of the total OH density possible by simultaneously measuring the absorption rates of different spectrally resolved rotational lines of the OH(A–X) transition. For different RF powers and water concentrations, OH densities and gas temperatures ranging between 6 × 1019and 4 × 1020 m−3 and 345 and 410 K, respectively, were obtained. The gas temperature Tg was also measured by three different methods. Tg deduced from the rotational temperature of N2(C–B) emission, nitrogen being present as a trace impurity, provided the most reliable value. The rotational temperature Tr of the ground state OH(X) presented values with a maximum deviation of 25 K compared with Tg. To obtain the gas temperature from the emission intensities of OH(A–X) rotational lines, the recorded intensities of different lines must be corrected for the effect of self-absorption inside the plasma.

A homogeneous dielectric barrier discharge plasma excited by a bipolar nanosecond pulse in nitrogen and air

In this paper, a nanosecond bipolar pulse voltage with 20 ns rise time is employed to generate a low gas temperature homogeneous dielectric barrier discharge plasma both in nitrogen and air at atmospheric pressure. Images of the discharge, waveforms of pulse voltage and discharge current, and the optical emission spectra emitted from the discharge are recorded successfully under severe electromagnetic interference. The effects of pulse peak voltage, pulse repetition rate and the gap distance between electrodes on gas temperature and the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 are discussed. It is found that the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 rise with increasing both pulse peak voltage and pulse repetition rate but decrease with gap distance between the electrodes when it is above 2.5 mm. The effect of concentrations of O2 on the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 is also investigated, and it is found that the emission intensities of both NO (A 2Σ → X 2Π) and OH (A 2Σ → X 2Π) reach maximum values when the O2 concentration is 0.3%.

A dc non-thermal atmospheric-pressure plasma microjet

A direct current (dc), non-thermal, atmospheric-pressure plasma microjet is generated with helium/oxygen gas mixture as working gas. The electrical property is characterized as a function of the oxygen concentration and show distinctive regions of operation. Side-on images of the jet were taken to analyze the mode of operation as well as the jet length. A self-pulsed mode is observed before the transition of the discharge to normal glow mode. Optical emission spectroscopy is employed from both end-on and side-on along the jet to analyze the reactive species generated in the plasma. Line emissions from atomic oxygen (at 777.4 nm) and helium (at 706.5 nm) were studied with respect to the oxygen volume percentage in the working gas, flow rate and discharge current. Optical emission intensities of Cu and OH are found to depend heavily on the oxygen concentration in the working gas. Ozone concentration measured in a semi-confined zone in front of the plasma jet is found to be from tens to ∼120 ppm. The results presented here demonstrate potential pathways for the adjustment and tuning of various plasma parameters such as reactive species selectivity and quantities or even ultraviolet emission intensities manipulation in an atmospheric-pressure non-thermal plasma source. The possibilities of fine tuning these plasma species allows for enhanced applications in health and medical related areas.

Experimental and theoretical study of acetic-acid decomposition by a pulsed dielectric-barrier plasma in a gas–liquid two-phase flow

Decomposition of acetic acid as a persistent material in water was demonstrated using a pulsed dielectric-barrier plasma in a gas–liquid two-phase flow. The plasma was driven by 35 kV, 200 Hz pulsed voltages and generated in oxygen bubbles in 20 ml solution having a concentration of 10–40 mgTOC l−1. The concentrations of ion species and hydrogen peroxide in the solution were analyzed by ion chromatography and absorptiometry, respectively. After 60 min of operation, the acetic acid was completely decomposed by the plasma. Optical measurements of the emission intensities of OH, H and O radicals suggest that the generated OH radicals are in the ground state in this study. A numerical calculation was carried out to analyze the radical generation processes in the gas phase and decomposition in the liquid phase. O-radical-induced generation of OH radical needed to be considered in the calculation of total organic carbon (TOC) and H2O2 concentrations in the solution. By considering such plasma–water interaction processes, data for the decomposition of acetic acid, which were in good agreement with experimental results, were obtained.