New evidence on the formation of oxidizing species in corona discharge in contact with liquid and their reactions with organic compounds.
The objective of these investigations is to understand in more detail how organic compounds in water are degraded during plasma treatment. The formation of oxidizing species (ozone (O3), hydrogen peroxide (H2O2) and hydroxyl radicals (OH)) in a pulsed corona discharge in contact with liquid is investigated. The degradation of a target organic compound (methylparaben) in aqueous solution was increased when combining plasma treatment with ozonation, using the O3generated in the discharge. Enhanced mass transfer of O3obtained in this plasma+O3configuration leads to a six fold increase of MeP oxidation rate. The evolution of oxidants concentration during treatment of MeP solutions provides information on their consumption in reactions with MeP and its oxidation products. The correlation of MeP degradation results (MeP removal and mineralization) with O3consumption and the identified reaction products confirms that although O3plays an important role in the degradation, for the mineralization OH radicals have an essential contribution. The concentration of OH radicals is diminished in the solutions containing MeP as compared to plasma-treated water, indicating OH consumption in reactions with the target compound and its degradation products. The concentration of H2O2in the liquid can be either increased or reduced in the presence of MeP, depending on its initial concentration. On the one hand, decomposition of H2O2by OH or O3is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation.
National Institute for Lasers, Plasma and Radiation Physics, Department of Plasma Physics and Nuclear Fusion, Atomistilor Str. 409, P.O. Box MG-36, 077125, Magurele, Bucharest, Romania. Electronic address: monimag@infim.ro.
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Magureanu
National Institute for Lasers, Plasma and Radiation Physics, Department of Plasma Physics and Nuclear Fusion, Atomistilor Str. 409, P.O. Box MG-36, 077125, Magurele, Bucharest, Romania.
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Dobrin
University of Bucharest, Faculty of Biology, Department of Systems Ecology and Sustainability, Splaiul Independentei 91-95, 050095, Bucharest, Romania.
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Bradu
National Institute for Lasers, Plasma and Radiation Physics, Department of Plasma Physics and Nuclear Fusion, Atomistilor Str. 409, P.O. Box MG-36, 077125, Magurele, Bucharest, Romania.
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Gherendi
National Institute for Lasers, Plasma and Radiation Physics, Department of Plasma Physics and Nuclear Fusion, Atomistilor Str. 409, P.O. Box MG-36, 077125, Magurele, Bucharest, Romania.
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Mandache
University of Bucharest, Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, Bd. Regina Elisabeta 4-12, 030016, Bucharest, Romania.
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Parvulescu
D055664:Electrochemical Techniques; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry; D010226:Parabens / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D016877:Oxidants; D010226:Parabens; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D010126:Ozone; C015358:methylparaben; D006861:Hydrogen Peroxide
Corona discharge; Hydrogen peroxide; Methylparaben; Non-thermal plasma; Ozone; Water treatment