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Treatment of methyl orange by nitrogen non-thermal plasma in a corona reactor: The role of reactive nitrogen species

2015; Elsevier BV; Volume: 300; Linguagem: Inglês

10.1016/j.jhazmat.2015.08.009

1873-3336

Bruno Mena Cadorin, Vitor Douglas Tralli, Elisa Ceriani, Luís Otávio de Brito Benetoli, Ester Marotta, Claudio Ceretta, Nito Ângelo Debacher, Cristina Paradisi,

Catalytic Processes in Materials Science

Methyl orange (MO) azo dye served as model organic pollutant to investigate the role of reactive nitrogen species (RNS) in non-thermal plasma (NTP) induced water treatments. The results of experiments in which MO aqueous solutions were directly exposed to N2-NTP are compared with those of control experiments in which MO was allowed to react with nitrite, nitrate and hydrogen peroxide, which are species formed in water exposed to N2-NTP. Treatment of MO was also performed in PAW, Plasma Activated Water, that is water previously exposed to N2-NTP. Both direct N2-NTP and N2-PAW treatments induced the rapid decay of MO. No appreciable reaction was instead observed when MO was treated with NO3− and H2O2 either under acidic or neutral pH. In contrast, in acidic solutions MO decayed rapidly when treated with NO2− and with a combination of NO2− and H2O2. Thorough product analysis was carried out by HPLC coupled with UV–vis and ESI–MS/MS detectors. In all experiments in which MO reaction was observed, the major primary product was a derivative nitro-substituted at the ortho position with respect to the N,N-dimethylamino group of MO. The reactions of RNS are discussed and a mechanism for the observed nitration products is proposed.