A kinetic study of enhancing effect by phenolic compounds on the hydroxyl radical generation during ozonation.
Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates O2- radical, OH radical, HO2 radical, OH-, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water among them. In the present study, the enhancing effects of several phenolic compounds; phenol, 2-, 3-, 4-monochloro, 2,4-dichloro, 2,4,6-trichlorophenol on OH radical generation were mathematically evaluated using the electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocities of DMPO-OH generation in ozonated water containing phenolic compounds were quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus, which was controlled by homemade software. The initial velocities of DMPO-OH generation increased as a function of the ozone concentration. The relation among ozone concentration, amount of phenolic compounds and the initial velocity (v0) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, v0 (10(-6) M/s) = (A' x [PhOHs (10(-9) M)] + 0.0005) exp (60 x [ozone (10(-9) M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.98.
Han
Y H
YH
Department of Bio-function Science, Faculty of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi, Fukuoka, Japan. hyh@pch.phar.kyushu-u.ac.jp
Ichikawa
K
K
Utsumi
H
H
D002733:Chlorophenols / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005069:Evaluation Studies as Topic; D017665:Hydroxyl Radical / Q000032:analysis* / Q000737:chemistry*; D007700:Kinetics; D010126:Ozone / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D002733:Chlorophenols; D010636:Phenols; D017665:Hydroxyl Radical; D010126:Ozone