Enhancing effect of organic substances on hydroxyl radical generation during ozonation of water: Stopped-flow ESR technique

Abstract

Generation of hydroxyl radical, one of their major active species in ozonation of water was directly observed with spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-pyrrolidine-1-oxyl (DMPO) as a spin-trapping reagent. Hydroxyl radical was trapped with DMPO as a stable radical, DMPO-OH. 80 mM of ozone produced 1.08 × 10-6M of DMPO-OH, indicating that 1.4% of ·OH is trapped with DMPO if ·OH is produced stoichiometrically from ozone. Humic acid suppressed DMPO-OH generation in a dose-dependent manner. Generation rate of DMPO-OH was determined with 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.