Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 300, Issue -, Pages 754-764Publisher
ELSEVIER
DOI: 10.1016/j.jhazmat.2015.08.009
Keywords
Nitrite; Nitrate; Hydrogen peroxide; Peroxynitrous acid; Mass spectrometry; Azo dyes
Categories
Funding
- CNPq [BEX 11024/13-5]
- CAPES/Ciencia sem Fronteiras [BEX 11024/13-5]
- University of Padova [CPDA147395/14]
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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 N-2-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 N-2-NTP. Treatment of MO was also performed in PAW, Plasma Activated Water, that is water previously exposed to N-2-NTP. Both direct N-2-NTP and N-2-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. (C) 2015 Elsevier B.V. All rights reserved.
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