2008 Volume 6 Issue 1 Pages 1-7
Hydroxyl (OH) radical is proposed as an important factor in the ozonation of water. It is necessary for the utilization of ozonation in the water treatment process to quantitatively determine the interaction among ozone, OH radical and dissolved substances during ozonation. In this study, the effect of humic acid on OH radical generation during ozonation was evaluated with ESR/spin-trapping/stopped-flow technique using resorcinol as a model compound of humic substances. The OH radical was trapped with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The initial velocity (ν0) of DMPO-OH generation increased as a function of ozone and resorcinol concentrations. The relation among ozone, resorcinol concentrations and the initial velocity (ν0) of DMPO-OH generation was kinetically analyzed using a power law equation and the following equation was obtained: ν0 ([DMPO-OH] 10-6 M/s) = (9.55 × 10-5) × [resorcinol (10-6 M)] × [ozone (10-6 M)]1.9 + (3.09 × 10-5) × [ozone (10-6 M)]1.72. The equation fitted the experimental results very well. This equation indicated that in the presence of 1 μM resorcinol, 1/3 of ozone concentration is enough to produce the same initial velocity of OH radical generation as that without resorcinol. The kinetic equation for the enhancing effect of resorcinol obtained in the present study should provide useful information to optimize the condition in ozone treatment process of water containing humic substances.
