Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session LW2: Plasmas in Liquids |
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Chair: Peter Bruggeman, University of Minnesota Room: State C |
Wednesday, November 5, 2014 3:30PM - 3:45PM |
LW2.00001: Advanced oxidation processes for wastewater treatment using a plasma/ozone combination system Nozomi Takeuchi, Yu Kamiya, Ryo Saeki, Kosuke Tachibana, Koichi Yasuoka Advanced oxidation process (AOP) using OH radicals is a promising method for the decomposition of persistent organic compounds in wastewater. Although many types of plasma reactors have been developed for the AOP, they are unsuitable for the complete decomposition of highly concentrated organic compounds. The reason for the incomplete decomposition is that OH radicals, particularly at a high density, recombine among themselves to form hydrogen peroxide. We have developed a combination plasma reactor in which ozone gas is fed, so that the generated hydrogen peroxide is re-converted to OH radicals. Pulsed plasmas generated within oxygen bubbles supply not only OH radicals but also hydrogen peroxide into wastewater. The total organic carbon (TOC) of the wastewater was more than 1 gTOC/L. The TOC values decreased linearly with time, and the persistent compounds which could not be decomposed by ozone were completely mineralized within 8 h of operation. [Preview Abstract] |
Wednesday, November 5, 2014 3:45PM - 4:00PM |
LW2.00002: Simulation with power circuit by modeling of plasmas within bubble in water Hayato Obo, Nozomi Takeuchi, Koichi Yasuoka Plasma is used in water treatments such as the decomposition of persistent compounds and the generation of chemically active species. We have developed a new plasma reactor with 21 treatment holes and successfully achieved the decomposition of organofluoric compounds by generating 21 plasmas in water. The equivalent circuit model of plasma within bubbles in water consists of plasma and water resistance. A typical plasma model consists of a Zener diode and cannot be used to express the transient state of plasma. In the Zener diode model, therefore, plasma cannot be simulated with a power circuit. In this work, we have developed a new equivalent circuit that consists of an ideal switch, a diode, and water resistance to model the plasma. With the circuit elements used in our model, it is possible to perform simulation of plasmas by modeling the generation as well as the extinction of plasma with a high voltage power circuit. We confirmed that the simulated voltage and current waveforms of the reactor were coincident with the experimental result by applying the variation of a plasma parameter in the plasma model. [Preview Abstract] |
Wednesday, November 5, 2014 4:00PM - 4:15PM |
LW2.00003: Physical and chemical interactions at the interface between atmospheric pressure plasmas and aqueous solutions Alexander Lindsay, Brandon Byrns, Detlef Knappe, David Graves, Steven Shannon Transport and reactions of charged species, neutrals, and photons at the interface between plasmas and liquids must be better quantified. The work presented here combines theoretical and experimental investigations of conditions in the gas and liquid phases in proximity to the interface for various discharges. OES is used to determine rotational and vibrational temperatures of OH, NO, and N$_{\mathrm{2}}^{\mathrm{+}}$; the relationship between these temperatures that characterize the distribution of internal energy states and gas and electron kinetic temperatures is considered. The deviation of OH rotational states from equilibrium under high humidity conditions is also presented. In contradiction with findings of other groups, high energy rotational states appear to become underpopulated with increasing humidity. In the aqueous phase, concentrations of longer-lived species such as nitrate, nitrite, hydrogen peroxide, and ozone are determined using ion chromatography and colorimetric methods. Spin-traps and electron paramagnetic resonance (EPR) are investigated for characterization of short-lived aqueous radicals like OH, O$_{\mathrm{2}}^{\mathrm{-}}$, NO, and ONOO$^{\mathrm{-}}$. Finally, experimental results are compared to a numerical model which couples transport and reactions within and between the bulk gas and liquid phases. [Preview Abstract] |
Wednesday, November 5, 2014 4:15PM - 4:30PM |
LW2.00004: ABSTRACT WITHDRAWN |
Wednesday, November 5, 2014 4:30PM - 4:45PM |
LW2.00005: Numerical simulation of plasma-induced electrolysis utilizing dc glow discharge Fumiyoshi Tochikubo, Naoki Shirai, Satoshi Uchida, Tatsuru Shirafuji In this work, we carried out one-dimensional numerical simulation of plasma-induced electrolysis, which consists of atmospheric pressure dc glow discharge and electrolyte solution connected in series. Grounded metal electrode is placed at the bottom of NaCl solution with 1 mm depth while powered electrode is placed at 1 mm above the solution surface. The gap is filled with helium. Continuity equations of charged species both in gas and in liquid were simultaneously calculated with Poisson's equation. Current continuity is considered at plasma-liquid interface. That is, hydrated electrons equivalent to electron flux from plasma, or H$_2$O$^+$ ions equivalent to positive ion flux from plasma are supplied in the liquid at plasma-liquid interface. The calculated gas-phase discharge structure is essentially the same as that between two metal electrodes. In front of the metal electrode in liquid, the electric double layer (EDL) with thickness of approximately 10 nm was formed to maintain the electrode reaction. However, the EDL was not formed at the liquid surface in contact with dc glow discharge, because charges are forcibly supplied from plasma to liquid. In other words, plasma-induced electrolysis is controlled at plasma-liquid interface by plasma. [Preview Abstract] |
Wednesday, November 5, 2014 4:45PM - 5:00PM |
LW2.00006: Control of plasma-liquid interaction of atmospheric DC glow discharge using liquid electrode Naoki Shirai, Ryuta Aoki, Aihito Nito, Takuya Aoki, Satoshi Uchida, Fumiyoshi Tochikubo Atmospheric plasma in contact with liquid have a variety of interesting phenomena and applications. Previously, we investigated the fundamental characteristics of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. We tried to control the plasma-liquid interaction by changing the plasma parameter such as gas species, liquid, and applied voltage. Sheath flow system enables another gas (N$_{2}$, O$_{2}$, Ar) flow to around the helium core flow. It can control the gas species around the discharge. When liquid (NaCl aq.) cathode DC discharge is generated, Na emission (588 nm) can be observed from liquid surface with increasing discharge current. Na emission strongly depends on the discharge current and liquid temperature. However, when Ar sheath flow is used, the intensity of Na becomes weak. When liquid anode DC discharge is generated, self-organized luminous pattern formation can be observed at the liquid surface. The pattern depends on existence of oxygen gas in gap. By changing the oxygen gas ratio in the gap, variety of pattern formation can be observed. The discharge in contact with liquid also can be used for synthesis of metal nanoparticles at plasma-liquid interface. Size and shape of nanoparticles depend on discharge gases. [Preview Abstract] |
Wednesday, November 5, 2014 5:00PM - 5:15PM |
LW2.00007: Characteristics of micro plasma generated on the nanoscale electrode in water Tomonari Aoyama, Hidemasa Fujita, Takehiko Sato, Toshiro Kaneko Discharges in water are anticipated for various applications such as nano material processing, organic compounds degradation, and bio-medical treatment. Especially, for the bio-medical application, there is a demand to generate micro scale plasma which is smaller than a cell to have an effect only on the selected cell. In this work, the electrodes with curvature radius of less than 1 $\mu$m are used and the streamer development from the electrode tip is observed. To characterize the streamers from the electrode tip, the relations among the discharge time, voltage, current, shadowgraph imaging, and optical emission are investigated. The shadowgraph imaging has the maximum time resolution up to 5 ns at resolution of 12 pixel/$\mu$m using a high magnification lens and a high speed camera. In the shadowgraph imaging, the streamers are observed at the minimum pulse voltage amplitude of 4 kV.Prior to the streamer development, the precursor of the streamer is formed around the tip of the nanoscale electrode. The maximum size of the precursor region is found to be 20 $\mu$m which corresponds to the typical cell size. These results show the feasibility of affecting a specific cell with micro scale discharge. [Preview Abstract] |
Wednesday, November 5, 2014 5:15PM - 5:30PM |
LW2.00008: Plasma Jet (V)UV-Radiation Impact on Biologically Relevant Liquids and Cell Suspension H. Tresp, R. Bussiahn, L. Bundscherer, A. Monden, M.U. Hammer, K. Masur, K.-D. Weltmann, Th. v. Woedtke, S. Reuter In this study the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH$_{2}$O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH$_{2}$O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals. [Preview Abstract] |
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