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This work investigated the decomposition of dilute N2O from gas streams with various oxygen contents by using a plasma-catalytic process over metal oxide catalysts supported on γ-Al2O3. Among the metals explored (Ru, Co, Cu, V, etc.), Ru was found to be the best catalyst for the decomposition of N2O in a plasma-catalytic reactor, and most of the experiments were conducted with alumina-supported Ru. The effects of applied voltage, reaction temperature, O2 content, gas flow rate and initial N2O content on the decomposition efficiency and byproducts formation were examined. Compared to the catalyst-alone case, the presence of plasma enhanced the decomposition efficiency by 30–50%, depending on the operating condition. The increase in the oxygen content from 0 to 20% largely decreased the catalytic decomposition efficiency, whereas in the presence of plasma N2O could be successfully decomposed even at 20% O2 content. The decomposition efficiency was not a strong function of the initial N2O concentration in the range of 225–1800 ppm, exhibiting pseudo first-order reaction kinetics. Without O2, there were negligible byproducts, but in the presence of O2, NO and NO2 were formed mainly due to the plasma-induced reactions between background molecules such as N2 and O2. The results obtained in this work showed the feasibility of plasma-catalytic process for the abatement of N2O.

// Jiao Jiao Zhang 1 , Jin Oh Jo 2 , Do Luong Huynh 1 , Mrinmoy Ghosh 1 , Nameun Kim 1 , Sang Baek Lee 2 , Hak Kyo Lee 3 , Young Sun Mok 2 , Taeho Kwon 4 and Dong Kee Jeong 1, 4 1 Department of Animal Biotechnology and Advance Next Generation Convergence Technology, Jeju National University, Jeju, Republic of Korea 2 Department of Chemical and Biological Engineering, Jeju National University, Jeju, Republic of Korea 3 Department of Animal Biotechnology, Chonbuk National University, Jeonju, Republic of Korea 4 Laboratory of Animal Genetic Engineering and Stem Cell Biology, Subtropical/Tropical Organism Gene Bank, Jeju National University, Jeju, Republic of Korea Correspondence to: Dong Kee Jeong, email: ngejeong@gmail.com Taeho Kwon, email: taehokwonk@gmail.com Young Sun Mok, email: smokie@jejunu.ac.kr Keywords: non-thermal DBD plasma, chicken embryo, ROS, NRF2, ATP Received: July 04, 2017 Accepted: September 03, 2017 Published: September 20, 2017 ABSTRACT In this study, we examined the effects of non-thermal dielectric barrier discharge plasma on embryonic development in chicken eggs in order to determine the optimal level of plasma exposure for the promotion of embryonic growth. We exposed developing chicken embryos at either Hamburger-Hamilton (HH) stage 04 or HH 20 to plasma at voltages of 11.7 kV to 27.6 kV. Our results show exposure at 11.7 kV for 1 min promoted chicken embryonic development, but exposure to more duration and intensity of plasma resulted in dose-dependent embryonic death and HH 20 stage embryos survive longer than those at stage HH 04. Furthermore, plasma exposure for 4 min increased the production of reactive oxygen species (ROS) and inactivated the nuclear factor erythroid 2-related factor 2 (NRF2)-antioxidant response signaling pathway, resulting in suppression of antioxidant enzymes in the skeletal muscle tissue of the dead embryos. We also found decreased levels of adenosine triphosphate production and reductions in the expression levels of several growth-related genes and proteins. These findings indicate that inappropriate plasma exposure causes dose-dependent embryonic death via excessive accumulation of ROS, NRF2-antioxidant signaling pathway disruption, and decreased growth factor expression.

Oxidative stress enhances cellular DNA oxidation and may cause mutations in DNA bases, including 8‑oxoguanine (8‑oxoG). Our recent study reported that exposure of cells to non‑thermal dielectric barrier discharge (DBD) plasma generates reactive oxygen species and damages DNA. The present study investigated the effect of non‑thermal DBD plasma exposure on the formation of 8‑oxoG in HaCaT human keratinocytes. Cells exposed to DBD plasma exhibited increased level of 8‑oxoG. In addition, mRNA and protein expression levels of 8‑oxoguanine glycosylase 1 (OGG1), an 8‑oxoG repair enzyme, were reduced in plasma‑exposed cells. Furthermore, the expression level of nuclear factor erythroid 2‑related factor 2 (Nrf2), a transcription factor that regulates OGG1 gene expression, was reduced following exposure to DBD plasma. Pretreatment of cells with an antioxidant, N‑acetyl cysteine (NAC), prior to plasma exposure suppressed the formation of 8‑oxoG and restored the expression levels of OGG1 and Nrf2. In addition, phosphorylation of protein kinase B (Akt), which regulates the activation of Nrf2, was reduced following plasma exposure. However, phosphorylation was restored by pretreatment with NAC. These findings suggested that non‑thermal DBD plasma exposure generates 8‑oxoG via inhibition of the Akt‑Nrf2‑OGG1 signaling pathway in HaCaT cells.

Combined removal of n-heptane and CO using a catalytic reactor coupled with dielectric barrier discharge plasma was investigated over several metal oxide catalysts including bare γ-Al 2 O 3 , Ag 2 O/γ-Al 2 O 3 , MnO/γ-Al 2 O 3 , RuO 2 /γ-Al 2 O 3 and PdO/γ-Al 2 O 3 . In order to effectively utilize the heat generated during plasma discharge for enhancing catalytic reactions, the plasma-catalytic reactor was thermally insulated by covering it with a glass wool jacket. Plasma propagated radially outward from the central high-voltage electrode with gradually increasing the applied voltage, and the temperature decreased with the radial distance due to the decreased plasma intensity, exhibiting a volcanic temperature distribution. The increased reactor temperature could improve the removal of CO and the selectivity toward CO 2 . The results obtained from separate experiments of n-heptane and CO removal showed that the PdO/γ-Al 2 O 3 was the best for the simultaneous removal purpose. The effects of specific input energy ( SIE ), oxygen content, reaction temperature and PdO loading on the simultaneous removal of n-heptane and CO and the formation of byproducts were examined. The removal efficiencies of n-heptane obtained with different catalysts were similar to one another, whereas the removal of CO strongly depended on the type of catalyst. The catalytic activity for the oxidation of CO followed the order: MnO/γ-Al 2 O 3 2 O/γ-Al 2 O 3 2 /γ-Al 2 O 3 2 O 3 . In the present plasma-catalytic hybrid reactor, the mixture of n-heptane and CO was mainly converted into CO 2 , and under an optimized condition, the selectivity toward CO 2 reached 100%.

This work investigated the decomposition of aqueous anatoxin-a originated from cyanobacteria using an underwater dielectric barrier discharge plasma system based on a porous ceramic tube and an alternating current (AC) high voltage. Plasmatic gas generated inside the porous ceramic tube was uniformly dispersed in the form of numerous bubbles into the aqueous solution through the micro-pores of the ceramic tube, which allowed an effective contact between the plasmatic gas and the aqueous anatoxin-a solution. Effect of applied voltage, treatment time and the coexistence of nutrients such as , and glucose on the decomposition of anatoxin-a was examined. Chemical analyses of the plasma-treated anatoxin-a solution using liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC) were performed to elucidate the mineralization mechanisms. Increasing the voltage improved the anatoxin-a decomposition efficiency due to the increased discharge power, but the energy required to remove a given amount of anatoxin-a was similar, regardless of the voltage. At an applied voltage of 17.2 kV (oxygen flow rate: ), anatoxin-a at an initial concentration of (volume: 0.5 L) was successfully treated within 3 min. The chemical analyses using LC-MS and IC suggested that the intermediates with molecular weights of 123~161 produced by the attack of plasma-induced reactive species on anatoxin-a molecule were further oxidized to stable compounds such as acetic acid, formic acid and oxalic acid.

Low-temperature conversion of nitrogen oxides using plasma-assisted hydrocarbon selective catalytic reduction of (HC-SCR) was investigated. Plasma was created in the catalyst-packed bed so that it could directly interact with the catalyst. The effect of the reaction temperature, the shape of catalyst, the concentration of n-heptane as a reducing agent, the oxygen content, the water vapor content and the energy density on NOx removal was examined. NOx conversion efficiencies achieved with the plasma-cata- lytic hybrid process at a temperature of 250 ℃ and an specific energy input (SIE) of 42 J L -1 were 83% and 69% for one-dimen- sional Ag catalyst (Ag (nanowire)/γ-Al2O3) and spherical Ag catalyst (Ag (sphere)/γ-Al2O3), respectively, whereas that ob- tained with the catalyst-alone was considerably lower (about 30%) even with Ag (nanowire)/γ-Al2O3 under the same condition. The enhanced catalytic activity towards NOx conversion in the presence of plasma can be explained by the formation of more reactive NO2 species and partially oxidized hydrocarbon intermediates from the oxidation of NO and n-heptane under plasma discharge. Increasing the SIE tended to improve NOx conversion efficiency, and so did the increase in the n-heptane concen- tration; however, a further increase in the n-heptane concentration beyond C1/NOx ratio of 5 did not improve the NOx conversion efficiency any more. The increase in the humidity affected negatively the NOx conversion efficiency, resulting in lowering the NOx conversion efficiency at the higher water vapor content, because water molecules competed with NOx species for the same active site. The NOx conversion efficiency increased with increasing the oxygen content from 3 to 15%, in particular at low SIE values, because the formation of NO2 and partially oxidized hydrocarbon intermediates was facilitated.

The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2′,7′-dichlorodihydro-fluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components.

This work investigated the size and shape effect of -alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/-alumina catalyst, the reduction efficiency in the range of increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for reduction was obtained with Ag wire, showing almost complete removal at a temperature of . For Cu and Ru catalysts, considerable amount of NO was oxidized to , rather than reduced to , leading to lower reduction efficiency.

The purpose of this study is to explain how plasma improves the performance of selective catalytic reduction (SCR) of nitrogen oxides (NOx) with a hydrocarbon reducing agent. In the plasma-coupled SCR process, NOx reduction was performed with n-heptane as a reducing agent over Ag/γ-Al2O3 as a catalyst. We found that the plasma decomposes n-heptane into several oxygen-containing products such as acetaldehyde, propionaldehyde and butyraldehyde, which are more reactive than the parent molecule n-heptane in the SCR process. Separate sets of experiments using acetaldehyde, propionaldehyde and butyraldehyde, one by one, as a reductant in the absence of plasma, have clearly shown that the presence of these partially oxidized compounds greatly enhanced the NOx conversion. The higher the discharge voltage, the more the amounts of such partially oxidized products. The oxidative species produced by the plasma easily converted NO into NO2, but the increase of the NO2 fraction was found to decrease the NOx conversion. Consequently, it can be concluded that the main role of plasma in the SCR process is to produce partially oxidized compounds (aldehydes), having better reducing power. The catalyst-alone NOx removal efficiency with n-heptane at 250 °C was measured to be less than 8%, but it increased to 99% in the presence of acetaldehyde at the same temperature. The NOx removal efficiency with the aldehyde reducing agent was higher as the number of carbons in the aldehyde was more; for example, the NOx removal efficiencies at 200 °C with butyraldehyde, propionaldehyde and acetaldehyde were measured to be 83.5%, 58.0% and 61.5%, respectively, which were far above the value (3%) obtained with n-heptane.

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the γ-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

An alternating-current-driven, atmospheric-pressure, non-thermal plasma reactor was applied to the degradation of dye in water. The plasma reactor, made of a porous hollow ceramic tube, was placed underwater and was able to disperse plasmatic gas containing various reactive species into aqueous dye solution as small bubbles through the micropores of the tube. The hydrophobic coating on the surface of the ceramic tube effectively prevented the water from permeating through it. This wastewater treatment system was able immediately to transfer plasmatic gas to aqueous solution across the porous ceramic tube and provide a large gas–liquid interfacial area, allowing efficient dye treatment. So as to simulate real dyeing wastewater, an aqueous solution comprising two different azo dyes was used. The effect of discharge power, treatment time, and flow rate of oxygen used for the creation of plasma was examined. The results suggest that this system may be useful for the treatment of organic wastewater.

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and V2O5 were supported on γ-Al2O3. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of V2O5/γ-Al2O3¤Ag/γ-Al2O3¤γ-Al2O3 from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of V2O5/γ-Al2O3¤γ-Al2O3¤Ag/γ-Al2O3, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with V2O5/γ-Al2O3, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: 1.0 L min; SIE: ~355 J L).

This work investigated the plasma-catalytic decomposition of isopropyl alcohol (IPA) and the behavior of the byproduct compounds over monolith-supported metal oxide catalysts. Iron oxide (Fe2O3) or copper oxide (CuO) was loaded on a monolithic porous α-Al2O3 support, which was placed inside the coaxial electrodes of plasma reactor. The IPA decomposition efficiency itself hardly depended on the presence and type of metal oxides because the rate of plasma-induced decomposition was so fast, but the behavior of byproduct formation was largely affected by them. The concentrations of the unwanted byproducts, including acetone, formaldehyde, acetaldehyde, methane, carbon monoxide, etc., were in order of Fe2O3/α-Al2O3 < CuO/α-Al2O3 < α-Al2O3 from low to high. Under the condition (flow rate: 1 L min -1 ; IPA concentration: 5,000 ppm; O2 content: 10%; discharge power: 47 W), the selectivity towards CO2 was about 40, 80 and 95% for α-Al2O3, CuO/α-Al2O3 and Fe2O3/α-Al2O3, respectively, indicating that Fe2O3/α-Al2O3 is the most effective for plasma-catalytic oxidation of IPA. Unlike plasma-alone processes in which tar-like products formed from volatile organic compounds are deposited, the present plasma-catalyst hybrid system did not exhibit such a phenomenon, thus retaining the original catalytic activity.

This work investigated the hydrophobic coating of silicate yellow phosphor powder in the form of divalent europium-activated strontium orthosilicate (Sr2SiO4:Eu 2+ ) by using an atmospheric pressure dielectric barrier discharge (DBD) plasma with argon as a carrier and hexamethyldisiloxane (HMDSO), toluene and n-hexane as precursors. After the plasma treatment of the phosphor powder, the lattice structure of orthosilicate was not altered, as confirmed by an X-ray diffractometer. The coated phosphor pow- der was characterized by scanning electron microscopy, fluorescence spectrophotometry and contact angle analysis (CAA). The CAA of the phosphor powder coated with the HMDSO precursor revealed that the water contact angle increased from 21.3° to 139.5° (max. 148.7°) and the glycerol contact angle from 55° to 143.5° (max. 145.3°) as a result of the hydrophobic coating, which indicated that hydrophobic layers were successfully formed on the phosphor powder surfaces. Further surface character- izations were performed by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry, which also evidenced the formation of hydrophobic coating layers. The phosphor coated with HMDSO exhibited a photoluminescence (PL) enhance- ment, but the use of toluene or n-hexane somewhat decreased the PL intensity. The results of this work suggest that the DBD plasma may be a viable method for the preparation of hydrophobic coating layer on phosphor powder.

A catalytic plasma reactor was employed for the oxidation of isopropyl alcohol (IPA) classified as a volatile organic com- pound (VOC). Copper oxide (Cu : 0.5% (w/w)) supported on a multichannel porous ceramic consisting of α-Al2O3 was used as a catalyst, which was directly exposed to the plasma created in it. The effects of discharge voltage and reaction temperature on the concentrations of IPA and its byproducts were examined to understand the behavior of the catalytic plasma reactor. Without thermal insulation, the reactor temperature increased up to 120 ℃ at an applied voltage of 17 kV (discharge power : 28 W), and the IPA at a flow rate of 1 L min -1 (O2 : 10% (v/v); IPA : 1000 ppm) was completely removed. At temperatures below 120 ℃, however, besides the desirable product CO2, several unwanted byproducts such as acetone, formaldehyde and CO were also formed from IPA. On the other hand, when the reactor was thermally insulated, the plasma discharge increased the temperature up to 265 ℃ under the same condition and most of IPA was oxidized to CO2. Without loading CuO on the ceramic support, the plasma discharge in the thermally insulated reactor produced nearly equal amounts of CO2 and CO. On comparison, with the catalyst alone (temperature : 265 ℃), more than 70% of the removed IPA was simply converted into another type of VOC (acetone), indicating that the catalyst assisted by the plasma is more effective in the oxidation of IPA than that of the catalyst-alone process.

This study was conducted to determine the effects of argon plasma on the growth of soybean [Glycine max (L.) Merr.] sprouts and investigate the regulation mechanism of energy metabolism. The germination and growth characteristics were modified by argon plasma at different potentials and exposure durations. Upon investigation, plasma treatment at 22.1 kV for 12 s maximized the germination and seedling growth of soybean, increasing the concentrations of soluble protein, antioxidant enzymes, and adenosine triphosphate (ATP) as well as up-regulating ATP a1, ATP a2, ATP b1, ATP b2, ATP b3, target of rapamycin (TOR), growth-regulating factor (GRF) 1–6, down-regulating ATP MI25 mRNA expression, and increasing the demethylation levels of the sequenced region of ATP a1, ATP b1, TOR, GRF 5, and GRF 6 of 6-day-old soybean sprouts. These observations indicate that argon plasma promotes soybean seed germination and sprout growth by regulating the demethylation levels of ATP, TOR, and GRF.

Atmospheric-pressure nonthermal corona discharge plasma was applied to the sterilization of biologically contaminated scoria powder. Escherichia coli (E. coli) culture solution was uniformly sprayed throughout the scoria powder for artificial in- oculation, which was well mixed to ensure uniformity of the batch. The effect of the key parameters such as discharge power, treatment time, type of gas and electrode distance on the sterilization efficiency was examined and discussed. The experimental results revealed that the plasma treatment was very effective for the sterilization of scoria powder; 5-min treatment at 15 W could sterilize more than 99.9% of E. coli inoculated into the scoria powder. Increasing the discharge power, treatment time or applied voltage led to an improvement in the sterilization efficiency. The effect of type of gas on the sterilization efficiency was in order of oxygen, synthetic air (20% oxygen) and nitrogen from high to low. The inactivation of E. coli under the influence of corona discharge plasma can be explained by cell membrane erosion or etching resulting from UV and reactive oxidizing species (oxygen radical, OH radical, ozone, etc.), and the destruction of E. coli cell membrane by the physical action of numerous corona streamers.

A red nitride phosphor with a chemical formula: ( Sr 0 . 8 Ca 0 . 2 ) AlSiN 3 :Eu 0 . 0075 2 + was successfully synthesized using spark plasma sintering at a temperature of 1680 °C from powder mixture of metal nitrides of Sr, Ca, Al, and Si and europium (III) oxide. The prepared phosphor showed a wide excitation band ranging from 300 to 550 nm and a broad emission band centered at a wavelength of about 618 nm, being suitable for use in down-conversion white LEDs. The effects of sintering temperature, holding time as well as uniaxial pressure on phosphor characteristics were investigated. Increasing the sintering temperature increased the crystallization and PL characteristics of the phosphor. The excitation and emission intensity of the phosphor was also affected by the holding time at the maximum temperature. When the synthesis was carried out at 1680 °C and 30 MPa, the optimal holding time was around 30 min. Increasing the uniaxial pressure resulted in the improvement of the excitation and emission intensity. The optical properties of the phosphor synthesized at an increased uniaxial pressure of 42 MPa (1680 °C for 30 min) was comparable to those of the commercial phosphor. The experimental results indicated that the spark plasma sintering method is a viable method to prepare nitride phosphors at relatively low temperatures in short synthesis time, compared to conventional methods.

This study investigated an underwater plasma water treatment system based on a porous hydrophobic hollow ceramic tube and an alternating current (AC) voltage source, and its application to the decomposition of taste-and-odor compounds originated from algae. The taste-and-odor compounds investigated were geosmin and 2-methyl isoborneol (2-MIB), and the decomposition of algae was carried out on cyanobacteria. The features of the present atmospheric-pressure plasma system employing a porous ceramic tube are large gas–liquid interfacial area due to the formation of numerous plasmatic gas bubbles and instant transfer of short-lived reactive species to water through the micro-pores of the ceramic tube right after the generation. The present plasma process was found to effectively decompose not only the taste-and-odor compounds but also the cyanobacteria algae. Both geosmin and 2-MIB were decomposed more rapidly in the raw river water than in the distilled water. The intermediate products resulting from the decomposition of the taste-and-odor compounds were identified, which showed that geosmin and 2-MIB underwent ring opening and subsequent bond cleavage at multiple sites. The specific energy inputs (SEIs) for 90% decomposition of algae ranged from 3.4 to 8.4 kJ L−1 for the initial concentration range of 129–1596 μg L−1. The decomposition efficiencies of the taste-and-odor compounds were well correlated with the SEI.

Decomposition of a volatile organic compound (ethylene) was carried out using nonthermal plasma created in a multihole porous ceramic membrane. The ceramic membrane employed as a low pressure drop catalyst support was loaded with manganese oxide capable of removing unreacted ozone. AC-driven discharge plasma was created inside the porous ceramic membrane to produce radicals, ozone, ions, and excited molecules available for the decomposition of ethylene. As the voltage applied to the plasma reactor was increased, the electrical discharge plasma gradually developed in the radial direction, and uniform plasma was produced in the entire ceramic membrane. The effects of specific energy input, initial ethylene concentration, and manganese oxide loading on the decomposition efficiency and the formation of byproducts were examined. It was found that the use of the manganese oxide-loaded ceramic membrane efficiently removed unreacted ozone while keeping the ethylene decomposition efficiency as high as the bare ceramic membrane case achieved. In addition, partially oxidized products such as formaldehyde, acetaldehyde, and formic acid greatly decreased by manganese loading.

Colorectal cancer is a common type of tumor among both men and women worldwide. Conventional remedies such as chemotherapies pose the risk of side‑effects, and in many cases cancer cells develop chemoresistance to these treatments. Non‑thermal gas plasma (NTGP) was recently identified as a potential tool for cancer treatment. In this study, we investigated the potential use of NTGP to control SNUC5 human colon carcinoma cells. We hypothesized that NTGP would generate reactive oxygen species (ROS) in these cells, resulting in induction of endoplasmic reticulum (ER) stress. ROS generation, expression of ER stress‑related proteins and mitochondrial calcium levels were analyzed. Our results confirmed that plasma‑generated ROS induce apoptosis in SNUC5 cells. Furthermore, we found that plasma exposure resulted in mitochondrial calcium accumulation and expression of unfolded protein response (UPR) proteins such as glucose‑related protein 78 (GRP78), protein kinase R (PKR)‑like ER kinase (PERK), and inositol‑requiring enzyme 1 (IRE1). Elevated expression of spliced X‑box binding protein 1 (XBP1) and CCAAT/enhancer‑binding protein homologous protein (CHOP) further confirmed that ROS generated by NTGP induces apoptosis through the ER stress signaling pathway.

A dielectric barrier discharge (DBD) reactor consisting of water-filled dielectric tube electrodes was used for the treatment of wastewater. The inner dielectric tube, which acted as the discharging electrode, was filled with an aqueous electrolyte solution. The outer dielectric tube, which served as the other electrode, was in contact with the wastewater, which was grounded. The present reactor system was energy-efficient for the production of ozone, not only because the perfect contact between the aqueous electrode and the dielectric surface minimized the loss of the electrical energy, but also because the DBD reactor was cooled by the wastewater. In addition, the ultraviolet (UV) light produced in the DBD reactor was able to assist in the wastewater treatment since the quartz tube used as the dielectric material was UV-transparent. The performance of the present DBD system was evaluated using a synthetic wastewater formed from distilled water and an azo dye, amaranth. The experimental parameters were the concentration of the electrolyte in the aqueous electrode, the discharge power, the initial pH of the wastewater and the concentration of hydrogen peroxide added to the wastewater. The wastewater treatment system was found to be effective for achieving decomposition of the dye.

The pulsed arc discharge to the surface of wastewater was applied to the degradation of a textile azo dye (Acid Red 27). A high-voltage electrode (discharging electrode) was vertically placed above the surface of the wastewater while the wastewater itself was grounded. The pulsed arc discharge occurred between the tip of the discharging electrode and the surface of the wastewater, producing various oxidative species. Oxygen was used as the working gas instead of air to prevent nitrogen oxides from forming. The effect of several parameters on the chromaticity and chemical oxygen demand (COD) removal was examined. The results obtained showed that the chromaticity of the wastewater was completely removed by this process and the COD also decreased significantly. It has been found that ozone formed in the gas phase mainly affects the removal of the dye. The contribution of other effects such as ultraviolet light emission and OH radical formation during the arc discharge to the degradation of the dye was found to be less than 15%. For the present reactor system, the optimum pH, pulse repetition rate and agitation speed were found to be 3.0, 110 Hz and 300 rpm, respectively.

Dielectric barrier discharge (DBD) is an effective method available for the production of ozone and ultraviolet light. The wastewater treatment system of this study was designed to utilize both ozone and ultraviolet light produced in the DBD reactor for the degradation of organic contaminant. The DBD reactor consisted of a quartz cylinder and a coaxial ceramic tube inside of which a steel rod was placed. The DBD reactor was immersed in the wastewater that was grounded. In this case, the wastewater acted not only as an electrode but also as the cooling medium for the DBD reactor. An azo dye, Acid Red 27, was used as the organic contaminant. In this system, the organic contaminant was degraded by two oxidation pathways induced by ozone and ultraviolet light. The concentration of ozone, the ultraviolet radiation intensity and the degradation efficiency of the organic contaminant were measured by varying the discharge. The results showed that the present system was very effective for the degradation of the organic contaminant. The energy requirement for the degradation was found to be 0.654 kJ/mg, which is much smaller value than those obtained with an ultraviolet/photocatalytic process.

Dielectric barrier discharge (DBD) was applied to the degradation of an organic contaminant in wastewater. When electrical discharge occurs, the DBD reactor produces oxidative species (ozone) and emits ultraviolet light. For the purpose of using both ozone and ultraviolet light for the degradation of the organic contaminant, the DBD reactor was immersed in the wastewater. The DBD reactor for this paper consisted of a quartz cylinder and a coaxial ceramic tube inside of which a steel rod was placed. High voltage was connected to the steel rod inside of the ceramic tube, and the wastewater was grounded. In this case, the wastewater acted not only as an electrode but also as the cooling medium for the DBD reactor. The performance of this DBD reactor system was evaluated with a simulated wastewater formed with distilled water and an azo dye (Acid Red 27) as the organic contaminant. The experimental results showed that this system was able to completely degrade the organic contaminant within 20 min at typical experimental condition. The energy requirement for the degradation of the organic contaminant was found to be 0.654 kJ/mg

This study investigated the degradation of an organic compound (an azo dye, Acid Red 4) in a synthetic wastewater by using dielectric barrier discharge (DBD) tube comprised of a hollow quartz cylinder and a coaxial copper rod. The DBD tube was immersed in the wastewater that was connected to the ground electrode. When AC high voltage was applied to the copper electrode, the electrical discharge occurred inside the quartz cylinder to produce ultraviolet (UV) light and reactive species such as ozone. The photocatalytic degradation of the organic compound with the UV emitted from the DBD tube was carried out in the presence of aluminum meshes coated with titanium oxide. The system further comprised a gas diffuser that distributed the ozone-containing gas produced in the DBD tube into the wastewater, such that the organic compound were degraded by reacting with ozone. The contributions of the photocatalysis and the ozonation to the degradation were separately assessed, and then combined effect on the degradation was examined. The results clearly revealed that the present system capable of degrading the organic compound in two ways (DBD-induced photocatalysis and ozonation) was very effective for the treatment of the wastewater.