Non Thermal Plasma

Non-thermal plasma jets in open air are composed of ionization waves commonly known as 'plasma bullets' propagating at high velocities. We present in this paper an experimental study of plasma bullets produced in a dielectric barrier discharge linear-field reactor fed with helium and driven by microsecond high-voltage pulses. Two discharges were produced between electrodes for every pulse (at the rising and falling edge), but only one bullet was generated. Fast intensified charge coupled device camera imaging showed that bullet velocity and diameter increase with applied voltage. Spatially resolved optical emission spectroscopy measurements provided evidence of the hollow structure of the jet and its contraction. It was shown that the pulse amplitude significantly enhances electron energy and production of active species. The plasma bullet appeared to behave like a surface discharge in the tube, and like a positive streamer in air. A kinetics mechanism based on electron impact, Penning effect and charge transfer reactions is proposed to explain the propagation of the ionization front and temporal behavior of the radiative species.

Conversion of carbon dioxide (CO 2 ) using gliding arc plasma was performed. The research was done to investigate the effect of variation of total gas flow rates and addition of auxiliary gases -N 2 , O 2 , air, water -to the CO 2 conversion process. This system shows higher power efficiency than other nonthermal plasma methods. Experiment results indicate the conversion of CO 2 reaches 18% at total gas flow rate of 0.8 L/min and produces CO and O 2 as the main gaseous products. Among auxiliary gases, only N 2 gives positive effect on CO 2 conversion and the power efficiency at N 2 concentration of 95% and total gas flow rate of 2 L/min increases about three times compared to pure CO 2 process.

The laboratory-scale behaviour of a methane–air mixture injected at atmospheric pressure and ambient temperature into a non-thermal plasma (NTP) reactor is investigated experimentally and numerically as a function of CH4 concentration and mass flow rate. Numerical simulations of the NTP reactor gas phase are performed with a chemical kinetic model used initially for CH4 oxidation in a perfectly stirred reactor (PSR). The computed H2, CO, CO2 and remaining CH4 mole fractions are in good agreement with experimental data. Syngas (H2 and CO) production from CH4–air mixture is demonstrated over a large range of fuel flow rates and methane amounts in air. The lowest energy cost of H2 production is about 45 kWh/kg(H2)45 kWh/kg(H2) for the highest mass flow rate. Numerical simulation has confirmed that the optimum use of electrical power by the NTP reactor is achieved for high mass flow rates and low inlet CH4 concentration in air.

Energy from biomass is becoming increasingly important as fossil fuel reserves diminish. The utilization of biomass is already prevalent in the domestic heating sector, but produces significant amounts of particulates that are detrimental to human health. Mitigation technologies are well-developed for largescale applications, but that is not the case at domestic scale. This review evaluates the various technologies that are available for mitigation of emissions from domestic combustion. Various other technologies are presented too, including those from the vehicular emissions field. The most common methods are the use of additives and catalysts, but both techniques are of limited effectiveness. The most notable technology is probably small scale electrostatic precipitators (ESP) which are under development and have been shown to be effective in reducing emissions.

In this study, methylene blue (MB) removal from an aqueous phase by electrical discharge non-thermal plasma (NTP) over water was investigated using three different feed gases: N2, Ar, and O2. The results showed that the dye removal rate was not strongly dependent on the feed gas when the electrical current was kept the same for all gases. The hydrogen peroxide generation in the water varied according to the feed gas (N2 < Ar < O2). Using O2 as the feed gas, pyrite was added to the reactor in acid medium resulting in an accentuated increase in the dye removal, which suggests that pyrite acts as a Fenton-like catalyst. The total organic carbon (TOC) content of the dye solution decreased slightly as the plasma treatment time increased, but in the presence of the pyrite catalyst the TOC removal increased substantially. The acute toxicity test using Artemia sp. microcrustaceans showed that the treated solution is not toxic when Ar, O2 or O2–pyrite is employed. Electrospray ionization mass spectrometry analysis (ESI-MS) of the treated samples indicated that the dye degradation occurs via high energy electron impact as well as successive hydroxylation in the benzene rings of the dye molecules.► We use O2 as the feed gas and pyrite was added to the non-thermal plasma reactor. ► The methylene blue removal by NTP increased in the presence of pyrite. ► The total organic carbon content decreased substantially. ► The acute toxicity test showed that the treated solution is not toxic. ► The dye degradation occurs via electron impact as well as successive hydroxylation.

The paper discusses non-thermal plasmas, their generation and characteristics, formation mechanisms of ozone and the treatment of volatile organic compounds (VOCs). In the experimental part, undecane (C 11 H 24 as model VOCs) was treated with assistance of low temperature plasma at an atmospheric pressure which was generated in the so-called stack reactor. The gas composition was 13% of oxygen in nitrogen with impurities of carbon dioxide, carbon monoxide and undecane. The formation of by-products, as well as the removal efficiency, were investigated.

Performance evaluation of non-thermal plasma (NTP) process has been carried out using NO as a model gas. The experimental results were evaluated using a simple model, which relates the change of NO concentration with specific input energy (SIE) (kJ/Nm 3 ). The results were also evaluated using the well-known parameters of energy cost, energy yield (EY) and Gvalue. As the SIE increased, the EY and the G-value decreased while the energy cost increased even under a given reaction condition. Based on these parameters best results were found in the smaller SIE region where the NO removal is poor. An approach has been developed to use the constant (hereafter referred to as energy constant k E (Nm 3 /kJ)) in a simple model to evaluate the system performance of non-thermal plasma reactor instead of conventional parameters. Unlike the three conventional parameters, the energy constant was not influenced by the SIE level under the range tested in the present work. The effects of various reaction conditions, such as initial concentration of NO, temperature, additive on the energy constant k E have been investigated. The comparison of k E values for different NO concentrations clearly showed that the NTP process is more efficient in treating gaseous pollutant in low concentration. The increase of NO concentration exponentially decreased the energy constant. Gas temperature showed a similar effect. The significance of the influence of the tested parameters on the energy constant k E has been found to be of the order of the gas composition, the initial concentration, and the gas temperature. Among the additives tested in this study, ethylene made the energy constant k E to a maximum value of 242 Â 10 À3 . r

The effectiveness of reactive oxygen species (ROS) generating airPHX equipment for reducing bacterial populations of Clostridium difficile, Methicillin Resistant Staphylococcus aureus (mRSA) and Pseudomonas aeruginosa on three (3) common contact surfaces; stainless steel (Austenitic 316), plastic (PVC) and linoleum (floor tile) were studied. Antimicrobial resistant pathogens pose an ongoing and increasing challenge to hospitals because they cause healthcare-associated infections (HAIs) during clinical treatment of patients. Coupons of stainless steel, plastic and linoleum were inoculated with each organism placed inside an experimental chamber were continuously treated with ROS for eight different hour increments from an airPHX advanced oxidation generator. ROS levels were continuously monitored prior to removing coupons for microbiological testing. Control coupon were similarly placed in the chamber and held at environmental conditions to determine natural decay of microbial populations through time. Stainless steel coupon results after 0.5 h of ROS treatment Clostridium difficile Methicillin Resistant Staphylococcus aureus (mRSA) and Pseudomonas aeruginosa saw a 4.21-log, 4.42-log and 4.26-log destruction respectively. After 12 h exposure these same organisms yielded a 6.87-log, 7.17-log and 7.71-log reduction, respectively. The other contact surfaces, plastic and linoleum displayed similar log reduction. These findings reveal that ROS treatment using the airPHX unit significantly reduces these three HAI’s on common health care contact materials to > 4.2-log destruction after a 0.5 h exposure.

Measurements on electron energy distribution function (EEDF) by a Langmuir probe show that inert gas mixing can change EEDF from a Maxwellian to a 'two-temperature' structure in an inductively coupled low pressure nitrogen discharge. This result suggests the existence of two groups of electrons: low and high energy. Each group of electrons has distinct behaviour as gas mixing ratio changes. As a result, this causes discrepancies between the measured electron temperature by a Langmuir probe and that by optical line-ratio technique, since these two techniques are sensitive to the energy distribution of low and high energy electrons, respectively. A detailed experimental investigation of the evolution of EEDF with different inert gas mixtures (Ar/N 2 , He/N 2 , Ne/N 2 and Xe/N 2 ) at an operating pressure of 10 mTorr is performed, from which the distribution temperature of both low and high energy electrons is calculated and compared with the temperature obtained from the Global Model. It is found that with the measured energy range and under the experimental condition studied, inelastic collisions (both excitation and ionization) play a key role on the shape of EEDF when inert gas is mixed in the discharge.

Aroma, aroma-active compounds and fatty acid profiles of Iranian olive oil obtained from the cv. Mari were investigated for the first time in the current study. Aroma extracts were isolated from the oil by using a purge and trap extraction system and their compositions were analyzed by gas chromatography-mass spectrometry-olfactometry (GC–MS-O). A total of 35 aroma compounds comprising alcohols, aldehydes, acids, esters, ketones, terpenes and volatile phenols were identified and quantified in the assayed samples. Aldehydes were present at the highest levels, followed by ketones and alcohols. (E)-2-Hexenal was quantitatively (1589 µg kg−1) the main aroma compound in the analyzed oils, followed by hexanal and (E)-2-heptenal. The aromaactive volatiles were elucidated in the aromatic extract by applying aroma extract dilution analysis (AEDA). The results of AEDA revealed 17 aroma-active compounds. Under these condition it was possible to completely identify 16 of these compounds. Regarding to the flavor dilution (FD) factor, the most potent odorants with the highest FD factor were (E)-2-hexenal (512), followed by hexanal, 6-methyl-5-hepten-2-one, (E)-2-decenal and one unknown compound (LRI = 1871). The fatty acid profile of the tested oils was composed of thirteen compounds. Oleic acid was the main fatty acid (76.01 %) followed by palmitic acid.

Physical properties of the high-current density spots (which are not the hot arc spots) formed on the electrodes due to development of electro-dynamical and ionization instabilities in the near-electrode layers are the subjects of this paper. The influence of these spots on homogeneity of the plasma column between the electrodes due to initiation of the discharge constriction is discussed and illustrated by the proper experimental data. The geometrical and gas-dynamic effects stabilizing the formation of the anode and cathode current spots at higher gas pressures are described.

The composition of the gas for the Surface Micro-Discharge (SMD) plasma system is changed by applying variety of binary mixtures with oxygen, nitrogen and argon. Gram-negative Escherichia coli and gram-positive Enterococcus mundtii bacteria strains are inoculated on agar and exposed to the plasma using different gas mixture ratios either with a fixed applied voltage or with a fixed dissipated power. No bacterial reduction is observed in the absence of oxygen. Higher bactericidal efficacy is observed with higher oxygen fraction in the gas composition for the plasma. A threshold of the oxygen fraction is found where the bacterial reduction does not change much. The strong correlation between the bactericidal efficacy and the ozone concentration measured by optical absorption spectroscopy suggests that ozone generated by the SMD plasma is the major agent for the bacterial inactivation under the investigated conditions.

This study is seeking to investigate the effect of non-thermal plasma technology in the abatement of particulate matter (PM) from the actual diesel exhaust. Ozone (O 3 ) strongly promotes PM oxidation, the main product of which is carbon dioxide (CO 2 ). PM oxidation into the less harmful product (CO 2 ) is the main objective whiles the correlation between PM, O 3 and CO 2 is considered. A dielectric barrier discharge reactor has been designed with pulsed power technology to produce plasma inside the diesel exhaust. To characterise the system under varied conditions, a range of applied voltages from 11 kV PP to 21kV PP at repetition rates of 2.5, 5, 7.5 and 10 kHz, have been experimentally investigated. The results show that by increasing the applied voltage and repetition rate, higher discharge power and CO 2 dissociation can be achieved. The PM removal efficiency of more than 50% has been achieved during the experiments and high concentrations of ozone on the order of a few hundreds of ppm have been observed at high discharge powers. Furthermore, O 3 , CO 2 and PM concentrations at different plasma states have been analysed for time dependence. Based on this analysis, an inverse relationship between ozone concentration and PM removal has been found and the role of ozone in PM removal in plasma treatment of diesel exhaust has been highlighted.

Hybrid plasma catalyst technology has great potential for indoor air purification. However, humidity is a critical parameter in plasma catalytic processes. In this work, several catalysts were tested downstream of a DC corona discharge and the effect of humidity was investigated on both ozone and toluene removal. Next, sorption measurements onto the catalysts were performed for toluene, trichloroethylene and acetone, using an equilibrium partitioning in closed system procedure to explain the obtained results in a quantitative manner.

An atmospheric air non-thermal plasma (NTP)
device is characterized in relation to ozone production. The electron density, ne, electron temperature, Te and ozone concentration are measured for three dielectric barrier discharge (DBD) geometries, i.e., ten tubes of 10 mm outer diameter (OD), six tubes of 25 mm OD, and three tubes of 40 mm OD. ne and Te are deduced using optical emission
spectroscopy via the line ratio method and the ozone concentrations are measured by using an ozone meter. ne and ozone concentrations were the highest for the three tube-40 mm configuration, showing a correlation between the number of charged particles and ozone production.

We use O 2 as the feed gas and pyrite was added to the non-thermal plasma reactor. The methylene blue removal by NTP increased in the presence of pyrite. The total organic carbon content decreased substantially. The acute toxicity test showed that the treated solution is not toxic. The dye degradation occurs via electron impact as well as successive hydroxylation.

The degradation of an endocrine disruptor (ED), the bisphenol A (BPA), was studied using Gliding Arc Discharge (GAD). This kind of discharge generates a non-thermal plasma at atmospheric pressure and quasi-ambient temperature. The resulting plasma is the source of several chemical reactions that lead to the hydroxyl radical formation. Hydroxyl radicals, • OH, are very powerful and non-selective oxidizing agents (E • •OH/H 2 O 2.8 V vs. normal hydrogen electrode) able to degrade compounds resistant to conventional treatment. GAD belongs to the group of advanced oxidation processes (AOPs).

The use of elevated temperatures to pasteurize food products leads to a loss of food quality, which stimulates research into novel nonthermal processes for food preservation. Using nonthermal plasma discharges, applied directly into the food product, proved effective in reducing the number of Escherichia coli O157:H7 cells in apple juice, by up to 7 log units. The pulsed nonthermal plasma system was developed and used to study the effects of different process parameters on the inactivation. The process parameters considered were discharge voltage, pulse number, and pulse frequency. The apple juice used had a pH of 4 and a conductivity of 2.29 mS / cm.

Effectiveness of non-thermal atmospheric pressure Floating Electrode Dielectric Barrier Discharge plasma in interaction with living organisms is investigated. Two regimes are analyzed: where this plasma comes in direct contact with the organism and where this plasma in separated for the treatment target by a grounded mesh. Direct plasma contact is found to be more efficient at sterilization and the mechanism is hypothesized to be due to charged species delivered by plasma to the surface of the organism.

There has been an increasing recent research interest in the removal of NOx from combustion gases using electrical discharges, especially pulsed corona discharge reactors. The major issues in development of this technology are (a) the energy consumption required to achieve the desired pollutant reduction; and (b) the formation of undesirable byproducts. In this study, the transformations and destruction of nitrogen oxides—NO, NO2 and N2O—were investigated in a pulsed corona discharge reactor. Gas mixtures—NO in N2, N2O in N2, NO2 in N2 and NO–N2O–NO2 in N2—were allowed to flow through the reactor with initial concentrations, flow rates and energy input as operating variables. The reactor effluent gas stream was analyzed for N2O, NO, NO2, by means of an FTIR spectrometer. In some experiments, oxygen was measured using a gas chromatograph.Reaction mechanisms were proposed for the transformations and destruction of the different nitrogen oxides within a unified model structure. The corresponding reaction rates were integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and fluid flow within the reactor. It was recognized that the electron-impact dissociation of the background gas N2 leads to both ionic and radical product species. In fact, ionic reactions were found responsible for N2O destruction. Radical reactions were dominant in the transformation and destruction of NO and NO2. However, decomposition of N2+ ions also leads to indirect production of N radicals; this appears to be a less-power intensive route for NO destruction though longer residence times may be necessary. In addition, the decomposition of N2+ ions limits the N2O destruction that can be achieved. Comparison with our experimental data, as well as data in the literature, was very encouraging.

Fuel cell systems for automotive applications are nowadays an important research activity. No infrastructure for distributing hydrogen still exists and the research efforts are thus focused on on-board hydrogen generation from hydrocarbon reforming. Experimental catalytic reformers have already been developed but their cost, their low time of life due to sulphur and carbon pollution problems make these reformers unusable for a commercial application. This paper presents a non-thermal gliding arc system designed to convert gasoline into hydrogen-rich gas in auto-thermal or steam reforming conditions for car application. In a first part, the chemistry of hydrocarbon reforming is briefly explained. The technology and design of the plasma reactor composed of two gliding arc in series is detailed in a second part. Finally, we demonstrate the feasibility of producing hydrogen in both auto-thermal and steam reforming conditions. The attention is focused on the influence of the different operating parameters (pressure, temperature, air and steam ratio, inlet flow rates) on the reformer efficiency and the composition of the produced gas. The experimental results are then compared to the performances of other non-thermal plasma reformers. This new plasma reformer is at its first stage of development and several technological optimisations can be performed to improve its chemical efficiency.

Non-thermal plasma (NTP) devices produce excited and radical species that have higher energy levels than their ground state and are utilized for various applications. There are various types of NTP devices, with dielectric barrier discharge (DBD) reactors being widely used. These DBD
devices vary in geometrical configuration and operating parameters, making a comparison of their performance in terms of discharge power characteristics difficult. Therefore, this study proposes a dimensionless parameter that is related to the geometrical features, and is a function
of the discharge power with respect to the frequency, voltage, and capacitance of a DBD. The dimensionless parameter, in the form of a ratio of the discharge energy per cycle to the gap capacitive energy, will be useful for engineers and designers to compare the energy characteristics of devices systematically, and could also be used for scaling up DBD devices. From the results in this experiment and from the literature, different DBD devices are categorized into three separate groups according to different levels of the energy ratio. The larger DBD devices have lower energy ratios due to their lower estimated surface discharge areas and capacitive reactance. Therefore, the devices can be categorized according to the energy ratio due to the effects of the geometrical features of the DBD devices, since it affects the surface
discharge area and capacitance of the DBD. The DBD devices are also categorized into three separate groups using the Kriegseis factor, but the categorization is different from that of the energy ratio.

Please cite this article as: Schiavon M, Scapinello M, Tosi P, Ragazzi M, Torretta V, Rada EC, Potential of non-thermal plasmas for helping the biodegradation of VOCs released by waste management plants, Abstract 3 This paper investigates the feasibility of exploiting a non-thermal plasma (NTP) to treat the gaseous 4 effluents released by the mechanical-biological treatments (MBTs) of waste and overcome the 5 typical disadvantages of biofilters, whose removal efficiency is limited during acclimatization of 6 bacteria, peaks of pollutant concentration or unstable airflow rates. A dielectric barrier discharge 7 was applied to two mixtures of volatile organic compounds (VOCs) and air. Ethanol and ethyl 8 acetate (Mixture 1) and benzene, toluene and octane (Mixture 2), in addition to being typical 9 constituents of the waste air released by MBTs of waste, also represent real emissions from two 10 specific sectors that use biofiltration for air pollution control (APC): the printing (Mixture 1) and 11 the petrochemical industries (Mixture 2). At the highest specific energy densities applied to the 12 discharge (900-2520 J L -1 ), all the initial VOCs were removed by 95-100%. With respect to ethyl 13 acetate, the maximal CO 2 selectivity and the maximal energy yield resulted in 62-70% and 6-11 g 14 kW -1 h -1 , respectively; with regards to benzene, the same parameters resulted in 52-90% and 0.17-15 0.72 g kW -1 h -1 , respectively. At medium-low energy, acetaldehyde and acetic acid were detected as 16 the main byproducts of Mixture 1, while several trace compounds were found as the byproducts of 17 Mixture 2. Interestingly, the byproducts generated are more polar than the initial compounds and, 18 thus, their solubility in water is higher. Therefore, NTPs can be considered as a promising 19 technology to help the biodegradation of VOCs in facilities where biofilters are used as APC 20 systems.

The oxidation of toluene in air was investigated using a dielectric barrier discharge (DBD) combined with a Pd/Al 2 O 3 catalyst. When using only plasma, rather low selectivity toward CO 2 was obtained: 32-35%. By filling the DBD reactor with Pd/Al 2 O 3 catalyst the CO 2 selectivity was significantly enhanced (80-90%), however, a large amount of toluene was desorbed from the catalyst when the discharge was operated. By filling a quarter of the discharge gap with catalyst and placing the rest of the catalyst downstream of the plasma reactor, an important increase of CO 2 selectivity (∼75%) and a 15% increase in toluene conversion were achieved as compared to the results with plasma alone. The catalyst exhibited a very good stability in this reaction.

A comparison has been made of plasma-catalysis with thermal-catalysis and plasma alone for the removal of low concentrations of propane and propene from synthetic air using a one-stage, catalyst-in discharge configuration. In all cases, plasma-catalysis produces better hydrocarbon destructions (*40%) than thermal catalysis at low temperatures. At higher temperatures, little difference is observed between plasma-catalytic and thermal-catalytic operation. Plasma operation by itself had a similar effectiveness to plasma-catalysis at low temperatures but was significantly lower (up to 50%) as the temperature was raised. By examining the form of the temperature dependence for the plasma-catalytic destruction processes, it is possible to phenomenologically distinguish two contributions to the destruction; one that is specifically plasma-induced and another (at higher temperatures) in which both plasma and thermal activation have similar mechanisms.

The absorption of SO 2 from the gas mixtures of SO 2 /N 2 into deionized water was measured under corona discharge at 22°C and 1 atm. A model based on film theory was developed to evaluate the effects of mass-transfer enhancement in the liquid phase by chemical dissociations and corona discharge current. It has previously been reported that mass transfer in the gas phase is enhanced by corona discharge. In this study, it was also found that corona discharge enhances mass transfer in the liquid phase through liquid-side boundary-layer thinning caused by corona-induced surface vibrations. The liquid boundary layer decreases as the corona power is increased. For our experimental conditions, mass transfer was enhanced by about 5.5 times in the gas phase and about 2.3 times in the liquid phase.

Based on their high NO x storage capacities (NSCs), a series of M/Ba/Al (M = Mn, Fe, Co, Ni, Cu) catalysts were evaluated in NO x storage-reduction catalysis. Although the M/Ba/Al catalysts exhibited high NSC values, they exhibited much lower activity during lean-rich cycling compared with a traditional Pt/Ba/Al catalyst, indicating that regeneration of stored NO x is the rate limiting step for the M/Ba/Al samples. By employing an H 2 -plasma in the rich phase to assist reduction of the stored NO x , the NO x conversion was greatly improved, especially at low temperature.

Effectiveness of non-thermal atmospheric pressure Floating Electrode Dielectric Barrier Discharge plasma in interaction with living organisms is investigated. Two regimes are analyzed: where this plasma comes in direct contact with the organism and where this plasma in separated for the treatment target by a grounded mesh. Direct plasma contact is found to be more efficient at sterilization and the mechanism is hypothesized to be due to charged species delivered by plasma to the surface of the organism.

A non-thermal, atmospheric pressure, packed-bed plasma reactor has been used to study the effect of temperature on the plasma-catalytic destruction of toluene and benzene in air using two catalyst positions. TiO 2 and g-Al 2 O 3 supports, and Ag (0.5 wt.%) impregnated catalysts of both supports, were used to determine their effects. The reactor (in the one-stage configuration) or the downstream catalyst (in the two-stage arrangement) could be heated to $600 8C and the destruction efficiencies for toluene and benzene were determined. Plasma catalysis is more effective at destroying benzene and toluene than both conventional thermal-catalysis and plasma alone. Toluene is destroyed much more efficiently than benzene, regardless of the temperature of the system and the reactor configuration. A one-stage, plasma-catalysis configuration is found to be more effective at destroying both toluene and benzene than a two-stage configuration. Plasma catalysis offers no advantage over thermal catalysis for destroying both pollutants in the two-stage configuration. #

The decomposition of a model pharmaceutical compound, pentoxifylline, in aqueous solution was investigated using a dielectric barrier discharge (DBD) in coaxial configuration, operated in pulsed regime, at atmospheric pressure and room temperature. The solution was made to flow as a film over the surface of the inner electrode of the plasma reactor, so the discharge was generated at the gaseliquid interface. Oxygen was introduced with a flow rate of 600 sccm. After 60 min plasma treatment 92.5% removal of pentoxifylline was achieved and the corresponding decomposition yield was 16 g/kWh. It was found that pentoxifylline degradation depended on the initial concentration of the compound, being faster for lower concentrations. Faster decomposition of pentoxifylline could be also achieved by increasing the pulse repetition rate, and implicitly the power introduced in the discharge, however, this had little effect on the decomposition yield. The degradation products were investigated by liquid chromatographyemass spectrometry technique (LCeMS). The evolution of the intermediates during plasma treatment showed a fast increase in the first 30 min, followed by a slower decrease, so that these products are almost completely removed after 120 min treatment time.

Objectives: (1) To chemically characterise Y-TZP surface via X-ray photoelectron spectroscopy (XPS) and evaluate the surface energy levels (SE) after non-thermal plasma (NTP). (2) To test the microtensile bond strength (MTBS) of Y-TZP bonded to cured composite disks, after a combination of different surface conditioning methods. Methods: Twenty-four Y-TZP discs (13.5 mm  4 mm) were obtained from the manufacturer and composite resin (Z-100) discs with similar dimensions were prepared. All discs were polished to 600 grit and divided into 8 groups (n = 3 disks each), four control (non-NTP treated) and four experimental (NTP treated for 10 s) groups. All groups received one of the four following treatments prior to cementation with Rely  Unicem cement: sand-blasting (SB), a Clearfil ceramic primer (MDP), sand-blasting + MDP (SBMDP), or baseline (B), no treatment. SE readings and surface roughness parameters were statistically analysed (ANOVA, Tukey's, p < 0.05). Mixed model and paired samples t-tests were used to compare groups on MTBS. Results: XPS showed increase in O and decrease in C elements after NTP. The polar component increased for BP (42.20 mN/m) and SBP (43.77 mN/m). MTBS values for groups BP (21.3 MPa), SBP (31 MPa), MDPP (30.1 MPa) and SBMDPP (32.3 MPa) were significantly higher in specimens treated with NTP than their untreated counterparts B (9.1 MPa), SB (14.4 MPa), MDP (17.8 MPa) and SBMDP (24.1 MPa). Conclusions: (1) Increase of O and decrease of C led to higher surface energy levels dictated by the polar component after NTP; (2) NTP application increased MTBS values of Y-TZP surfaces.

C n F 2n−2 O 2 H + ) which are suggested to derive from C n F 2n+1 + in a cascade of steps initiated by condensation with water followed by steps of HF elimination and H 2 O addition. Negative ions formed from the fluoroethanes CHF 2 CH 3 and CF 3 CH 2 F (M) include complexes with ions of the background, O 2 − (M), O 3 − (M) and some higher complexes involving also water, and complexes of the fluoride ion, F − (H 2 O), F − (M) and higher complexes with both M and H 2 O also together. The interesting product O 2 − (HF) is also formed from 1,1-difluoroethane. In contrast to the HFCs, perfluoro-n-hexane gives stable molecular anions, M − , which at low source temperature or in humidified air are also detected as hydrates, M − (H 2 O). In addition, in humidified air F − (H 2 O) n complexes are also formed. The reactions leading to all major positive and negative product ions are discussed also with reference to available thermochemical data and relevant literature reports. The effects on both positive and negative APCI spectra due to ion activation via increasing V cone are also reported and discussed: several interesting endothermic processes are observed under these conditions. The results provide important information on the role of ionic reactions in non-thermal plasma processes. Contract/grant sponsor: Università di Padova.

This paper deals with the NOx removal with the help of a non-thermal surface plasma discharge in wet conditions. The gas treatment device consisting of a surface discharge and a wet-type reactor, was characterized through FTIR and electrical measurements. The ability of the proposed system for the cleaning of gas exhaust was studied. NOx as gaseous pollutant was decomposed effectively. To improve the chemical conversion, a coil was inserted in the electric circuit then a catalyst was placed in the plasma area. Results showed an improvement of NOx removal by an increase in radical species produced and synergistic effect, respectively.

Method of biochemical patterning which allows for micro-and nano-scale resolution on nonplanar substrates is presented. Utilizing this method, bio-molecules (including DNA, proteins, and enzymes) can be delivered to charged locations on surfaces by charged water buffer droplets. Charging of water droplets is accomplished using dielectric barrier discharge (DBD) plasma. DBD was effectively stabilized in the presence of high concentration of micron-size water droplets. The concepts of the proposed method, as well as first experimental results supporting the idea are discussed in this paper.

The composition of the gas for the Surface Micro-Discharge (SMD) plasma system is changed by applying variety of binary mixtures with oxygen, nitrogen and argon. Gram-negative Escherichia coli and gram-positive Enterococcus mundtii bacteria strains are inoculated on agar and exposed to the plasma using different gas mixture ratios either with a fixed applied voltage or with a fixed dissipated power. No bacterial reduction is observed in the absence of oxygen. Higher bactericidal efficacy is observed with higher oxygen fraction in the gas composition for the plasma. A threshold of the oxygen fraction is found where the bacterial reduction does not change much. The strong correlation between the bactericidal efficacy and the ozone concentration measured by optical absorption spectroscopy suggests that ozone generated by the SMD plasma is the major agent for the bacterial inactivation under the investigated conditions.

The chemistry induced by atmospheric pressure DC discharges above a water surface in CO 2 /N 2 /H 2 O mixtures was investigated. The gaseous mixtures studied represent a model prebiotic atmosphere of the Earth. The most remarkable changes in the chemical composition of the treated gas were the decomposition of CO 2 and the production of CO. The concentration of CO increased logarithmically with the increasing input energy density and an increasing initial concentration of CO 2 in the gas. The highest achieved concentration of CO was 4.0 ± 0.6 vol. %. The production of CO was crucial for the synthesis of organic species, since reactions of CO with some reactive species generated in the plasma, e. g. H• or N• radicals, were probably the starting point in this synthesis. The presence of organic species (including the tentative identification of some amino acids) was demonstrated by the analysis of solid and liquid samples by high-performance liquid chromatography, infrared absorption spectroscopy and proton-transfer-reaction mass spectrometry. Formation of organic species in a completely inorganic CO 2 /N 2 /H 2 O atmosphere is a significant finding for the theory of the origins of life.

The removal of N 2 O by a pulsed corona reactor (PCR) was investigated. Gas mixtures containing N 2 O were allowed to¯ow in the reactor at various levels of energy input, and for different background gases,¯ow rates, and initial pollutant concentrations. The reactor ef¯uent gas stream was analyzed for N 2 O, NO, NO 2 , by means of an FTIR spectrometer. It was found that destruction of N 2 O was facilitated with argon as the background gas; the conversion dropped and power requirements increased when nitrogen was used as the background gas. Reaction mechanisms are proposed for the destruction of N 2 O in dry argon and nitrogen. Application of the pseudo-steady state hypothesis permits development of expressions for the overall reaction rate in these systems. These reaction rates are integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and¯uid¯ow within the reactor. Comparison with experiment is encouraging, though the needs for additional research are clearly identi®ed.

h i g h l i g h t s Efficient removal of diclofenac in water was obtained by pulsed corona discharge. Diclofenac in solution was completely removed after 15 min plasma treatment. Total Organic Carbon (TOC) decreased by 50% after 30 min exposure to plasma. No chlorinated degradation products are present at the end of plasma treatment. Short-chain carboxylic acids were detected as by-products in the treated solution.

Effectiveness of non-thermal atmospheric pressure Floating Electrode Dielectric Barrier Discharge plasma in interaction with living organisms is investigated. Two regimes are analyzed: where this plasma comes in direct contact with the organism and where this plasma in separated for the treatment target by a grounded mesh. Direct plasma contact is found to be more efficient at sterilization and the mechanism is hypothesized to be due to charged species delivered by plasma to the surface of the organism.

The chemistry induced by atmospheric pressure DC discharges above a water surface in CO2/N2/H2O mixtures was investigated. The gaseous mixtures studied represent a model prebiotic atmosphere of the Earth. The most remarkable changes in the chemical composition of the treated gas were the decomposition of CO2 and the production of CO. The concentration of CO increased logarithmically with the increasing input energy density and an increasing initial concentration of CO2 in the gas. The highest achieved concentration of CO was 4.0 ± 0.6 vol. %. The production of CO was crucial for the synthesis of organic species, since reactions of CO with some reactive species generated in the plasma, e. g. Hriptstylebullet or Nriptstylebullet radicals, were probably the starting point in this synthesis. The presence of organic species (including the tentative identification of some amino acids) was demonstrated by the analysis of solid and liquid samples by high-performance liquid chromatography, infrared absorption spectroscopy and proton-transfer-reaction mass spectrometry. Formation of organic species in a completely inorganic CO2/N2/H2O atmosphere is a significant finding for the theory of the origins of life.

The plasma-chemical degradation of Forafac 1110, a perfluorinated non-ionic surfactant, in aqueous solutions was investigated using TiO 2 catalysts. The considered plasma was the gliding arc in humid air, which results from an electric discharge at atmospheric pressure and quasi-ambient temperature. Two titanium dioxide powders were used and their synergistic effects on the Forafac degradation were compared. The results were discussed through the evolution of the pH, the conductivity, the fluoride ions concentration released in solutions, the surfactant concentration remaining after treatment and the chemical oxygen demand (COD) measurement.

Non-thermal plasmas (NTP) are partially ionized gases that represent a promising technology for seed treatment to enhance seed health while promoting germination and vigor in a fast, cost-effective, and eco-friendly way. The seed treatment with NTP generates phenotypic variations in plants that could be related to changes in DNA methylation. This work analyses the effects of two different NTP: nitrogen for 3 min (PMN3) and oxygen for 2 min (PMO2) applied to soybean (Glycine max) seeds. Growth parameters of plants grown from treated and untreated seeds were evaluated at two growth stages: 6 and 20 days after sowing (DAS). MSAP (Methylation Sensitive Amplified Polymorphism) markers were assayed to evaluate epigenetic changes induced by NTP treatments. Plants obtained from PMN3 and PMO2-treated seeds were phenotypically similar to each other: exhibited a superior growth at both stages. At 6 DAS root and shoot length and fresh weight surpassed the Control, while at 20 DAS root length and fresh and dry weight were higher than Control. PMN3 and PMO2 induced DNA methylation changes with respect to the Control plants, with higher differentiation at 20 DAS than at 6 DAS. The epigenetic variability and the phenotypic variability correlated only at 20 DAS (R 2 = 0.5). The observed phenotypic differences among Control and NTP-treated plants could not be explained by overall changes in the methylation levels, but both demethylation and methylation changes at specific loci appear to be operating in response to NTP treatments.

A report is given on the ionization/dissociation behavior of the title compounds within air plasmas produced by electrical corona discharges at atmospheric pressure: both positive and negative ions were investigated at different temperatures using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). CHF(2)CH(3) (HFC-152a) undergoes efficient ionic oxidation to C(2)H(5)O(+), in which the oxygen comes from water present in the plasma. In contrast, CF(3)CH(2)F (HFC-134a) does not produce any characteristic positive ion under APCI conditions, its presence within the plasma being revealed only as a neutral ligand in ion-molecule complexes with ions of the background (H(3)O(+) and NO(+)). Analogously, the perfluorocarbon FC-72 (n-C(6)F(14)) does not produce significant positive ions at 30 degrees C: at high temperature, however, it undergoes dissociative ionization to form many product ions including C(3)F(6)(+), C(2)F(4)(+), C(n)F(2n+1)(+) and a few families of oxygen co...

In the field of wound healing research non-thermal plasma (NTP) increasingly draws attention. Next to its intensely studied antibacterial effects, some studies already showed stimulating effects on eukaryotic cells. This promises a unique potential in healing of chronic wounds, where effective therapies are urgently needed. Immune cells do play an important part in the process of wound healing and their reaction to NTP treatment has yet been rarely examined. Here, we studied the impact of NTP treatment using the kinpen on apoptotic and proliferative cell signaling pathways of two human immune cell lines, the CD4 + T helper cell line Jurkat and the monocyte cell line THP-1. Depending on NTP treatment time the number of apoptotic cells increased in both investigated cell types according to a caspase 3 assay. Western blot analysis pointed out that plasma treatment activated pro-apoptotic signaling proteins like p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase 1 and 2 (JNK 1/2) in both cell types. Stronger signals were detected in Jurkat cells at comparable plasma treatment times. Intriguingly, exposure of Jurkat and THP-1 cells to plasma also activated the pro-proliferative signaling molecules extracellular signal-regulated kinase 1/2 (ERK 1/2) and MAPK/ERK kinase 1 and 2 (MEK 1/2). In contrast to Jurkat cells, the anti-apoptotic heat shock protein 27 (HSP27) was activated in THP-1 cells after plasma treatment, indicating a possible mechanism how THP-1 cells may reduce programmed cell death. In conclusion, several signaling cascades were activated in the examined immune cell lines after NTP treatment and in THP-1 monocytes a possible defense mechanism against plasma impacts could be revealed. Therefore, plasma might be a treatment option for wound healing.

Characteristics of a dielectric barrier discharge were investigated experimentally to clarify an influence of an electrode configuration on ozone synthesis and a microdischarge behavior. Three difference configurations: plane, trench and multipoint were employed as ground electrode. The alumina dielectric barrier coated plane electrode was used as a high-voltage electrode, to which a sinusoidal high-voltage was applied with 10 kHz frequency. Pure oxygen gas was fed into the reactor with gas flow rate of 5 L/ min. The maximum yielding rate increased from 80 to 120 g/kWh by changing an electrode configuration from plane to multipoint, which has 528 number of a right-pyramid shape projection on a 6 cm  22 cm plane electrode. The yielding rate was strongly dependent on a produced ozone concentration in the plane electrode case, whereas slightly depended on the concentration in the multipoint electrode case. The electrode configuration also affected a number of the microdischarges per one applied voltage cycle. The multipoint electrode showed the largest number of microdischarges at same input energy.

The oxidation of toluene in air was investigated using a dielectric barrier discharge (DBD) combined with a Pd/Al 2 O 3 catalyst. When using only plasma, rather low selectivity toward CO 2 was obtained: 32-35%. By filling the DBD reactor with Pd/Al 2 O 3 catalyst the CO 2 selectivity was significantly enhanced (80-90%), however, a large amount of toluene was desorbed from the catalyst when the discharge was operated. By filling a quarter of the discharge gap with catalyst and placing the rest of the catalyst downstream of the plasma reactor, an important increase of CO 2 selectivity (∼75%) and a 15% increase in toluene conversion were achieved as compared to the results with plasma alone. The catalyst exhibited a very good stability in this reaction.