title: Treatment of methyl orange by nitrogen non-thermal plasma in a corona reactor: The role of reactive nitrogen species.
abstract: 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.
authors: Department of Chemistry, Universidade Federal de Santa Catarina, Brazil. Electronic address: brunomenacadorin@gmail.com.
authors: Bruno Mena
authors: BM
authors: Cadorin
authors: Department of Chemistry, Universidade Federal de Santa Catarina, Brazil.
authors: Vitor Douglas
authors: VD
authors: Tralli
authors: Department of Chemical Sciences, Università di Padova, Italy.
authors: Elisa
authors: E
authors: Ceriani
authors: Department of Chemistry, Universidade Federal de Santa Catarina, Brazil.
authors: Luís Otávio de Brito
authors: LOB
authors: Benetoli
authors: Department of Chemical Sciences, Università di Padova, Italy. Electronic address: ester.marotta@unipd.it.
authors: Ester
authors: E
authors: Marotta
authors: Department of Industrial Engineering, Università di Padova, Italy.
authors: Claudio
authors: C
authors: Ceretta
authors: Department of Chemistry, Universidade Federal de Santa Catarina, Brazil.
authors: Nito Angelo
authors: NA
authors: Debacher
authors: Department of Chemical Sciences, Università di Padova, Italy.
authors: Cristina
authors: C
authors: Paradisi
keywords: Azo dyes; Hydrogen peroxide; Mass spectrometry; Nitrate; Nitrite; Peroxynitrous acid