Non-thermal Plasma System Research Articles

Remarkable promotion effect of lauric acid on Mn-MIL-100 for non-thermal plasma-catalytic decomposition of toluene

Here, lauric acid (LA) with a remarkable tailoring property of pore structure and porosity was adopted as modulator for the synthesis of Mn-MIL-100. Results reveal that LA amount has a significant effect on the morphology, crystal size and porous structure of prepared materials. The synthesized catalysts were coupled with a dielectric barrier discharge reactor to improve toluene decomposition performance. We found that the introduction of catalysts can remarkably enhance toluene removal efficiency (TRE), CO2/COx selectivity and energy yield (EY), and simultaneously inhibit the generation of O3 and NOx compared with the non-thermal plasma (NTP) system as the presence of catalysts with developed hierarchical porous structure and well-dispersed crystal particle provides abundant adsorbed centers and active sites for surface reactions. Amongst, LA-8 sample shows the best catalytic performance with TRE, CO2 and COx selectivity of 94.7%, 44.9% and 92.4%, respectively (specific energy density (SED) of 473 J L−1), much higher than the NTP system (respectively; 63.3%, 34.2% and 73.6%). Moreover, the EY of NTP-Catalysis system (5.19 g kWh−1) is also obviously higher than that of single NTP (1.94 g kWh−1) at SED of 262 J L−1. This work paves a way for application of MOFs in NTP-Catalysis system for VOC decomposition.

Simultaneous Removal of NO and SO2 via an Integrated System of Nonthermal Plasma Combined with Catalytic Oxidation and Wet Electrostatic Precipitator

An integrated system of dielectric barrier discharge (DBD) combined with MnCu/Ti catalyst and wet electrostatic precipitator (DBD–catalyst–WESP) was constructed for simultaneous removal of SO2 and NO. The removal mechanism and the effects of special energy density (SED) and initial concentrations of NO and SO2 on oxidation efficiency were investigated. Experimental results showed that compared with Mn/Ti and Cu/Ti, the MnCu/Ti catalyst exhibited a higher dispersion of active constituents and has more catalytic oxidation active substances. The removal efficiencies of NO and SO2 in the DBD-catalyst system increased with increasing SED (15–275 J/L), and the lower the initial concentration was, the higher were the simultaneous removal efficiencies of NO and SO2. The competitive relationship between the removal of NO and SO2 was clarified. Compared with the DBD–catalyst system, the DBD–catalyst–WESP system significantly improved the simultaneous removal efficiencies of NO and SO2. With low initial concentratio...

Non‐thermal plasma‐assisted catalytic oxidation of NO in a dielectric barrier discharge reactor packed with MOx/Al2O3 (M = Mn or Co) as catalysts

AbstractBACKGROUNDPlasma catalysis has emerged as a powerful tool in converting a gas or gas mixture into other value‐added or environment‐friendly chemicals. However, a substantial research effort is needed to further understand the physical and chemical interactions between plasma and catalysts, and their contribution to the chemical reactions.RESULTSFor a given energy density (ED) of 535 ± 25 J L−1, a dielectric barrier discharge (DBD) reactor packed with Al2O3 achieved higher NO2 selectivity and N2O concentration than the DBD reactor alone. Two kinds of supported catalysts (MnOx/Al2O3 and CoOx/Al2O3) with different loading amounts were prepared to investigate the NO oxidation performance of the plasma‐catalytic process. The results indicated that 5 wt% MnOx/Al2O3 presented higher NO2 selectivity and N2O concentration than other catalysts. Packing the DBD reactor with catalysts also changed its discharge behavior. The discharge behavior of the packed‐bed DBD reactor also changed with variation in the loading amount of active metal oxide from 0 to 15 wt%, resulting in changes in NO oxidation performance. Fourier transform infrared (FTIR) and temperature‐programmed desorption (TPD) analysis results indicated that nitrates were formed during the non‐thermal plasma (NTP)‐assisted catalytic process.CONCLUSIONPacking catalysts into the NTP area can not only change the discharge behavior but also improve the oxidation performance of NTP. Both NO oxidation performance and N2O formation for the NTP‐assisted catalytic process have presented significant enhancement. Reducing N2O formation will still be a big challenge for NTP systems used in environmental applications. © 2019 Society of Chemical Industry

Mechanisms of Xylene Isomer Oxidation by Non-thermal Plasma via Paired Experiments and Simulations

Xylene is a widely used solvent and industrial chemical, but it is also considered to be a volatile organic compound (VOC) pollutant. Meanwhile, non-thermal plasma (NTP) is a potential method for remediating VOC contaminants, especially aromatic hydrocarbons. During NTP degradation of xylene, the different oxidation mechanisms of three isomers, p-xylene, o-xylene and m-xylene, have attracted lots of attention but not been studied at the molecular level. In this study, the individual degradation rates of xylene isomers in a NTP system are measured. The results show the oxidation degradation rates have the following order: o-xylene > p-xylene ≈ m-xylene. Molecular dynamics simulations with an applied external electric field were adopted to examine the oxidation process of xylene isomers, as well. The oxidation rates from the simulations were calculated, the order of which is in a good agreement with the experimental results. The oxidation pathways of xylene isomers were analyzed more thoroughly to explain the rate differences. The external electrical field is found to have two effects: one is to speed up the oxidation rate of xylene isomers overall, and the other is to alter the oxidation pathways to increase the probability of the faster ring cleavage pathways of o-xylene.

Removal of benzene by non-thermal plasma catalysis over manganese oxides through a facile synthesis method.

Three manganese oxide catalysts (MnOx) were synthesized via a simple method, and then they were introduced into the non-thermal plasma (NTP) system for benzene removal. The XRD and EXAFS results showed the MnOx were mainly in the Mn3O4 phase, and from the analysis of N2 adsorption/desorption isotherms, we knew the MnOx calcined at 250°C (Mn250) had the largest surface area of 274.5m2g-1. Besides, Mn250 also exerted higher benzene adsorption capacity (0.430mmolg-1) according to C6H6-TPD. O2-TPD indicated that Mn250 showed better oxygen mobility than Mn300. Moreover, by analyzing XPS results, it revealed that Mn250 exhibited rich abundant of surface adsorbed oxygen species (Oads) and moderate ratio of Mn4+/Mn3+, and the reducibility temperature was also the lowest among all the MnOx catalysts drawn by H2-TPR profiles. As a result, Mn250 combined with NTP could remove 96.9% of benzene at a low input power of 3W (benzene concentration 200ppm, and GHSV 60,000mLgcat.-1h-1), performing the best catalytic activity among the three catalysts and plasma only. Furthermore, the "NTP + Mn250" system also produced the highest CO2 concentration and lowest CO concentration in downstream, and the residual O3 after catalytic reaction was also the lowest, that is to say, the synergistic effect between NTP and Mn250 was more effective than other catalysts in benzene removal. Graphical abstract.

Non-Thermal Plasma as a Unique Delivery System of Short-Lived Reactive Oxygen and Nitrogen Species for Immunogenic Cell Death in Melanoma Cells.

Breakthroughs in cancer immunotherapies have demonstrated considerable success, though not without limitations. Non‐thermal plasma (NTP) for cancer therapy has been emerging as a potential adjuvant treatment via induction of immunogenic cell death (ICD). Cancer cells undergoing ICD stimulate a patient's immune system to mount an anticancer response. While promising, the underlying mechanisms of NTP‐induced ICD must be closely examined. Here, the interaction between non‐thermal plasma and cancerous cells is studied. The short‐lived reactive oxygen and nitrogen species (e.g., hydroxyl radicals, atomic oxygen, nitric oxide) produced by plasma are the main effectors that elicit ICD in melanoma while, surprisingly, persistent species do not. This is demonstrated in vitro using a dielectric barrier discharge plasma system and is validated in a vaccination assay in vivo. Plasma generation of reactive species appears to be dictated by the total energy. Collectively, this work provides fundamental insight into plasma interactions with biological material. Furthermore, it lays the foundation for future development of NTP systems for clinical translation. The addition of plasma systems into the existing arsenal of cancer therapies opens the possibility for new combination strategies for safer and more robust control of cancer.

E. Coli Bactria Deactivation by Plasma Jet with Replica Plate Technique

In this research, non-thermal plasma system (plasma jet) of argon gas is designed to work at normal atmospheric pressure and suitable for work as well as use in medical and biotechnological applications, also applied this technique in the treatment of The E. Coli bacteria and show the role of the applied voltage on the killing rate of bacteria, and we obtained a 100% killing rate during the time of 5 minutes.

Influence of admixing oxygen on Ar plasma discharge for organic pollutant degradation in wastewater treatment

In previous study, non-thermal plasma system with addition of O2 gas was proven to accelerate the decolorization process of dye solution, resulting in faster treatment of the synthetic wastewater. The present study deals with the influence of variation of O2 gas admixing to the Ar plasma discharge to examine the decolorization of methylene blue solution underwater through measurement of absorbance value of the plasma-treated solution by UV/VIS measurement. From the experiments it was found that the best result of methylene blue solution decomposition was obtained from the application of Ar 0.3 lpm with the admixing of O2 gas 0.3 lpm in an underwater plasma system generated at 1.56 kV. Modelling the decomposition process of methylene blue by using Ar+O2 plasma with variation of O2 flow rate, it was found that the system was confirmed to follow the first order kinetics equation. From this study it could be said that the plasma-based oxidation process is promising for the application in the decomposition of textile wastewater to support sustainable industry with environmentally friendly orientation.

Degradation and mineralization of ciprofloxacin by gas–liquid discharge non-thermal plasma

A typical quinolones antibiotic ciprofloxacin (CIP) in aqueous solution was degraded by a gas–liquid discharge non-thermal plasma system. The discharge plasma power and the emission intensity of the excited reactive species (RS) generated in the gas phase were detected by the oscilloscope and the optical emission spectroscopy. The effects of various parameters on CIP degradation, i.e. input powers, initial concentrations addition of radical scavengers and pH values were investigated. With the increase of discharge power, the degradation efficiency increased but the energy efficiency significantly reduced. The degradation efficiency also reduced under high concentration of initial CIP conditions due to the competitive reactions between the plasma-induced RS with the degradation intermediates of CIP. Different radical scavengers (isopropanol and CCl4) on ·OH and H· were added into the reaction system and the oxidation effects of ·OH radicals have been proved with high degradation capacity on CIP. Moreover, the long-term degradation effect on CIP in the plasma-treated aqueous solution proved that the long-lived RS (H2O2 and O3, etc) might play key roles on the stay effect through multiple aqueous reactions leading to production of ·OH. The degradation intermediates were determined by the method of electrospray ionization (+)-mass spectroscopy, and the possible degradation mechanism were presented.

Aqueous methylparaben degradation by dielectric barrier discharge induced non-thermal plasma combined with ZnO-rGO nanosheets

The feasibility of methylparaben (MeP) degradation in aqueous solution by dielectric barrier discharge induced non-thermal plasma combined with zinc oxide-reduced graphene oxide (ZnO-rGO) nanosheets was investigated. The ZnO-rGO nanosheets were synthesized by hydrothermal method and characterized by X-ray diffraction, nitrogen adsorption-desorption isotherm, scanning electron microscope, transmission electron microscope, UV–vis absorption spectroscopy, photocurrent, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The effects of various factors (discharge power, initial concentration of MeP, initial pH value and air flow rate) on the degradation of MeP were evaluated and the changes of solution pH, conductivity and TOC during the degradation process were discussed. The results showed that when the discharge power was 20 W, the airflow rate was 20 L/h, the ZnO-rGO nanosheets dosage was 0.015 g/L, the initial concentration of MeP was 20 mg/L, and the initial pH value was 7.0, the degradation efficiency of MeP achieved 99% at 15 min. The adding of ZnO-rGO nanosheets to the non-thermal plasma system greatly enhanced the degradation efficiency of MeP. In addition, the role of some reactive species during the degradation process of MeP was also investigated. The degradation process of MeP was well fitted by the pseudo-first-order kinetics. Good stability of the synthetic ZnO-rGO was observed. The degradation intermediates of MeP were determined by gas chromatography-mass spectrometer and the degradation pathways were proposed. Under the attack of reactive species, conjugated structure destruction, hydroxylation, carboxylation and ring-opening reaction occurred during MeP degradation, resulting in the formation of organic acids and alcohols; furthermore, some of the degradation intermediates were mineralized to H2O and CO2.

The study of thermal description for non-thermal plasma needle system

Cold plasma is a relatively low temperature gas, so this feature enables us to use cold plasma to treat thermally sensitive materials including polymers and biologic tissues. In this research, the non-thermal plasma system is designed with diameter (3 mm, 10 mm) Argon at atmospheric pressure as well as to be suitable for use in medical and biotechnological applications.The thermal description of this system was studied and we observed the effect of the diameter of the plasma needle on the plasma, when the plasma needle slot is increased the plasma temperature decrease, as well as the effect of the voltages applied to the temperature of the plasma, where the temperature increasing with increasing the applied voltage . Results showed that the plasma temperature would be low, which enables the use of this system in many medical aspects.

The influence of argon gas flow in the killing of staphylococcus epidermidis bacteria

In this research, non-thermal plasma system of argon gas is designed to work at normal atmospheric pressure and suitable for work in medical and biotechnological applications. This technique is applied in the treatment of the Staphylococcus epidermidis bacteria and show the role of the flow rate of Argon gas on the killing rate of bacteria, and it obtained a 100 % killing rate during the time of 5 minutes at the flow Argon gas of 5 liters/ min.

Effect of high-voltage discharge non-thermal plasma on g-C3N4 in a plasma-photocatalyst system

The synergistic effect of high voltage discharge non-thermal plasma (NTP) and photocatalysts on contaminant removal has repeatedly confirmed by plenty of researches. Most previous plasma-photocatalyst synergistic systems focused on the utilization of the ultraviolet light but ignored the visible light generated by high voltage discharge. Graphitic carbon nitride (g-C3N4), a metal-free semiconductor that exhibits high chemical stability, can utilize both the ultraviolet and visible light from high voltage discharge. However, the synergistic system of NTP and g-C3N4 has been researched little. In this paper, the effect of NTP generated by dielectric barrier discharge (DBD) on g-C3N4 is studied by comparing the photocatalytic activities, the surface physical structure and the surface chemical characteristics of pristine and plasma treated g-C3N4. Experimental results indicate that the DBD plasma can change the physical structure and the chemical characteristics and to further affect the photocatalytic activity of g-C3N4. The effect of NTP on g-C3N4 is associated with the discharge intensity and the discharge time. For a long time scale, the effect of NTP on g-C3N4 photocatalysts presents a periodic change trend.

Toluene removal over TiO2-BaTiO3 catalysts in an atmospheric dielectric barrier discharge

Non-thermal plasma (NTP) combined with catalysts has been regarded as a promising approach for the removal of VOCs. In the present work, a series of TiO2-BaTiO3 catalysts were prepared by simple mechanical mixing. The performance of the catalysts on degradation of high concentration of toluene was investigated in a dielectric barrier discharge (DBD) plasma system. The effects of input power, mass ratio of Ti/Ba, gas flow rate and the initial concentration of toluene on the removal of toluene and the selectivity of CO2 as well as the energy yield have been investigated. The toluene removal efficiency and CO2 selectivity increased obviously in the plasma-catalytic system compared with the single NTP system. The removal efficiency of toluene with different catalysts abided by the following rules: Ti1Ba1 > Ti2Ba1 > Ti1Ba2 > BaTiO3 > TiO2. The reason for the best performance of Ti1Ba1 is that TiO2 offered the providential number of electron-hole pairs while BaTiO3 supplied the fitting number of high energy electrons. Additionally, the synergistic effects between TiO2 and BaTiO3 also reached its maximum in this case. The concentration of O3 in the exhaust gas was also detected and it reached the lowest point when Ti1Ba1 catalyst was packed in the discharge chamber.

Impact of plasma jet geometry on residence times of radical species

Numerous electrode geometries and power supplies, both commercial and in-house, have been employed for the generation of low-temperature atmospheric plasma jets. In this work, the development and operation of a 12 jet nonthermal atmospheric plasma system is presented. The study is based on optical spectroscopy as a diagnostic method due to its nonintrusive nature. A key focus of this study was the material selection (conductive and nonconductive), with several polymers screened for the jet design leading to polyacetal as the choice material. Their results are compared with other atmospheric plasma jet systems. The results show a significant increase in residence time and the spatial homogeneity for ambient air's main species, including: OH, O I, O2, O3, N2, and N2+. Their densities are studied with respect to treatment time, distance, duty cycle, and discharge frequency, as well as the jets' carrier gas chemistries (argon and helium). For their plasma jet system, the bulk of the chemical reactions occur in the surrounding atmosphere and not in the jet nozzle, which is different from most other plasma jet systems. The electron energy distribution function, for the given chemistries, is also reported.

Degradation of nicotine in water solutions using a water falling film DBD plasma reactor: direct and indirect treatment

Nicotine degradation efficiency in water solutions was studied using a water falling film dielectric barrier discharge (DBD) reactor. Two different treatments were applied: direct treatment, the recirculation of the solution through a DBD reactor, and indirect treatment, the bubbling of the gas from the DBD through the porous filter into the solution. In a separate experiment, samples spiked with nicotine in double distilled water (ddH2O) and tap water were studied and compared after both treatments. Furthermore, the effects of the homogeneous catalysts, namely, Fe2+ and H2O2, were tested in the direct treatment. Nicotine degradation efficiency was determined using high-performance liquid chromatography. A degradation efficiency of 90% was achieved after the direct treatment catalyzed with Fe2+. In order to analyze the biodegradability, mineralization level, and toxicity of the obtained solutions, after all degradation procedures the values of the following parameters were determined: total organic carbon, chemical oxygen demand, biochemical oxygen demand, and the Artemia salina toxicity test. The results showed that an increase in biodegradability was obtained, after all treatments. A partial nicotine mineralization was achieved and the mortality of the A. salina organism decreased in the treated samples, all of which indicating the effective removal of nicotine and the creation of less toxic solutions. Nicotine degradation products were identified using ultrahigh-performance liquid chromatography coupled with a linear ion trap Orbitrap hybrid mass spectrometer and a simple mechanism for oxidative degradation of nicotine in non-thermal plasma systems is proposed.

Effects of Multiple Pulses on Decomposition of Hydrocarbons for Hydrogen Production

Hydrogen production on vehicle is under development by using plasma discharges working in high-pressure condition over 1.5 atm. The original fuel for the system is methane (CH4) or propane (C3H8). For this purpose, mainly dielectric barrier discharge nonthermal plasma system is employed with high-voltage pulse of width 5– $30~\mu \text{s}$ and maximum amplitude 13 kV. This wide pulse is composed of multiple of 5- $\mu \text{s}$ pulse. In this system, no production of COx is expected. The decomposition rate of hydrocarbon depends on the applied pulsewidth. The phenomena of multiple pulse effects are discussed with use of multiple pulse decomposition model.

Composite CVOCs Removal in a Combined System of Nonthermal Plasma and a Biotrickling Filter

A coupling system of nonthermal plasma and a biotrickling filter was used to remove a gas mixture of chlorobenzene (CB) and dichloromethane (DCE). The effects of inlet gas concentration and gas flow rate on the removal of the target pollutants in the coupling system were investigated at the frequency of 10000 Hz and specific input energy (SIE) of 6111 J·L-1. Furthermore, the advantages of the plasma-bio-coupled system were revealed by analyzing the relationship between the degradation products and SIE, biomass, or biodiversity in the biotrickling filter. The results showed that when the SIE and gas flow rate were constant, increasing the initial concentration would decrease the removal efficiency of the mixed gas. The optimal appropriate gas flow rate was 0.71 L·min-1 when considering the cost. The CO2 production amount, CO2 selectivity, and chloride ion concentration increased with the increase of SIE when both the CB and DCE concentrations were 500 mg·m-3 and the gas flow rate was 0.71 L·min-1. The protein content of the biofilter column gradually increased as the reactor operation progressed, and the biomass of the lower layer was higher than that of the upper layer. The high-throughput sequencing analysis showed that the biological community in the biotrickling filter keeped rich and diversified.

Roller conveyer system for the reduction of pesticides using non-thermal gas plasma - A potential food safety control measure?

We previously described a novel roller conveyer plasma device, which generates gas plasma via atmospheric pressure dielectric barrier discharge, to disinfect vegetables in situ during the sorting process. Here, we tested this system to verify whether or not such treatment was also effective in pesticide reduction. Competitive enzyme-linked immunosorbent assay showed the pesticide malathion, present at levels typically observed on treated crops, was efficiently degraded to less than one tenth of the original level within 1 min. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) confirmed the decrease in the level of pesticide cocktail PL-14-2 and FA-2, including organophosphorus pesticides and other classes of pesticides, after plasma treatment. A cholinesterase inhibitory activity assay was used as an index to measure the activity of PL-14-2 and FA-2, which showed that the gas plasma treatment reduced the biological activity of the pesticides. In addition to its proven biocidal effects, our findings demonstrate the potential of this non-thermal plasma system as a food safety control measure ensuring reduction of pesticide residues in foodstuffs.

Non-thermal-plasma-activated de-NOx catalysis.

The combination of non-thermal plasma (NTP) with catalyst systems as an alternative technology to remove NOx emissions in the exhaust of lean-burn stationary and mobile sources is reviewed. Several factors, such as low exhaust gas temperatures (below 300°C), low selectivity to N2 and the presence of impurities, make current thermally activated technologies inefficient. Various hybrid plasma-catalyst systems have been examined and shown to have a synergistic effect on de-NOx efficiency when compared with NTP or catalyst-alone systems. The NTP is believed to form oxygenated species, such as aldehydes and nitrogen-containing organic species, and to convert NO to NO2, which improves the reduction efficiency of N2 during hydrocarbon-selective catalytic reduction reactions. The NTP has been used as a pretreatment to convert NO to its higher oxidation states such as NO2 to improve NOx reduction efficiency in the subsequent processes, e.g. NH3-selective catalytic reduction. It has been applied to the lean phase of the NOx storage to improve the adsorption capacity of the catalyst by conversion of NO to NO2 Alternatively, a catalyst with high adsorption capacity is chosen and the NTP is applied to the rich phase to improve the reduction activity of the catalyst at low temperature.This article is part of a discussion meeting issue 'Providing sustainable catalytic solutions for a rapidly changing world'.