Comparison of advanced oxidation processes in the decomposition of diuron and monuron-efficiency, intermediates, electrical energy per order and the effect of various matrices

János Farkas, Máté Náfrádi, Tamás Hlogyik, Bartus Cora Pravda, Krisztina Schrantz, Klára Hernádi, Tünde Alapi

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Abstract

The decomposition of diuron and monuron, widely used phenylurea pesticides, via UV-induced photolysis (UV254nm), ozonation (O3), their combination (UV254nm/O3) and heterogeneous photocatalysis (TiO2/UV) were investigated and compared. The UV254nm/O3 and TiO2/UV methods proved to be effective from the aspects of both the transformation and the mineralization. The transformation rates changed in the order: O3 ≪ TiO2/UV < UV254nm < UV254nm/O3. Comparing the electric energy per order (EcEO) values calculated for the transformation, the most efficient method was UV254nm/O3. However, the lowest ETOCEO value calculated for the mineralization was obtained using TiO2/UV. Identification of the aromatic intermediates revealed that the first step in the decomposition involves transformation of the aliphatic chain, in parallel with dechlorination and hydroxylation of the aromatic ring. The amount and quality of the intermediates formed depends strongly on the method applied. Matrices such as natural waters (from the River Tisza and thermal water from Kistelek) and inorganic salts exert significant effect on the transformation rates only in the case of TiO2/UV. Humic acids behave as "light filter" and consequently decrease the rate of photoinitiated transformation using UV254nm and UV254nm/O3 methods, whereas they slightly enhance the effect of ozonation, most likely because humic acids and/or their intermediates promote the decomposition of ozone and increase the radical concentration. Regarding this parameter, the most sensitive method was heterogeneous photocatalysis, most likely because the well adsorbed humic acid strongly inhibits the formation of hydroxyl radical.

Original languageEnglish
Pages (from-to)1345-1360
Number of pages16
JournalEnvironmental Science: Water Research and Technology
Volume4
Issue number9
DOIs
Publication statusPublished - Sep 2018

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ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology

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