ANALYSIS OF HYDROXYL RADICAL GENERATION IN ADVANCED OXIDATION PROCESS

-EFFECT OF HUMIC SUBSTANCES DURING OZONATION-

Abstract

Hydroxyl (OH) radical is one of the important reactive species in the advanced oxidation process. The objective of this study is to present the quantitative analysis of hydroxyl radical generation by using the electron spin resonance (ESR)/spin-trapping technique and to apply this method to evaluation of the enhancement of OH radical generation by several humic substances during ozonation in water. OH radical was trapped with a 5,5-dimethyl-1- pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The generation of OH radical was demonstrated with mathematical equation of the initial velocity of DMPO-OH generation, and the effect of the compounds, 3-chlorophenol and resorcinol, on OH radical generation expressed with ν0 (10^-6 M/s) = {9.7 ∼ 10.5 × [compound (10^-9 M)] + 0.0005} exp(57 × [ozone (10^-9 M)]). The effect of humic substances on OH generation was evaluated with the amount of DMPO-OH with batch system because of high viscosity of humic acid solution. The amount of DMPO-OH reached almost maximum level within 2 min and kept the level till 60 min in most cases. The amount of DMPO-OH depended both of the amounts of ozone and humic acid. The origin of humic acid also affected the amount of DMPO-OH.