Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

Hideo Utsumi, Sang Kuk Han, Kazuhiro Ichikawa

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20 Citations (Scopus)


Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 x 10-6 M of DMPO-OH, indicating that 1.4% of OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

Original languageEnglish
Pages (from-to)147-154
Number of pages8
JournalWater Science and Technology
Issue number6 pt 5
Publication statusPublished - 1998
Externally publishedYes
EventProceedings of the 1998 19th Biennial Conference of the International Association on Water Quality. Part 5 (of 10) - Vancouver, Can
Duration: Jun 21 1998Jun 26 1998

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Water Science and Technology


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