Removal of alachlor, diuron and isoproturon in water in a falling film dielectric barrier discharge (DBD) reactor combined with adsorption on activated carbon textile: Reaction mechanisms and oxidation by-products

•Oxidation pathways are investigated in a novel water treatment plasma reactor.•By-products of pesticides are identified from their fragmentation in HPLC-TOF-MS.•Nitrification is one of the five main oxidation steps under air plasma.•Nitrification is dominant for diuron and isoproturon but subordina...

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Bibliographic Details
Published in:Journal of hazardous materials 2018-07, Vol.354, p.180-190
Main Authors: Vanraes, Patrick, Wardenier, Niels, Surmont, Pieter, Lynen, Frederic, Nikiforov, Anton, Van Hulle, Stijn W.H., Leys, Christophe, Bogaerts, Annemie
Format: Article
Language:English
Subjects:
Advanced oxidation process
Aromatic micropollutants
Ozonation
Pesticides
Wastewater treatment
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Summary:•Oxidation pathways are investigated in a novel water treatment plasma reactor.•By-products of pesticides are identified from their fragmentation in HPLC-TOF-MS.•Nitrification is one of the five main oxidation steps under air plasma.•Nitrification is dominant for diuron and isoproturon but subordinate for alachlor.•Oxidation of the aromatic ring as well as of the side chains is observed. A falling film dielectric barrier discharge (DBD) plasma reactor combined with adsorption on activated carbon textile material was optimized to minimize the formation of hazardous oxidation by-products from the treatment of persistent pesticides (alachlor, diuron and isoproturon) in water. The formation of by-products and the reaction mechanism was investigated by HPLC-TOF-MS. The maximum concentration of each by-product was at least two orders of magnitude below the initial pesticide concentration, during the first 10 min of treatment. After 30 min of treatment, the individual by-product concentrations had decreased to values of at least three orders of magnitude below the initial pesticide concentration. The proposed oxidation pathways revealed five main oxidation steps: dechlorination, dealkylation, hydroxylation, addition of a double-bonded oxygen and nitrification. The latter is one of the main oxidation mechanisms of diuron and isoproturon for air plasma treatment. To our knowledge, this is the first time that the formation of nitrificated intermediates is reported for the plasma treatment of non-phenolic compounds.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2018.05.007