Photosensitized production of hydrogen peroxide in the aqueous system containing dissolved organic carbon

Abstract

When aqueous solutions containing dissolved organic carbon (DOC) were irradiated with UV light (>290 nm), the generation of H2O2 at the μM level was observed. The kinetic constants of the photoproduction of H2O2 (K DOC) were evaluated for the case of humic (HA), oxalic (OA) and gallic (GA) acids, respectively. The K DOC value for GA was approximately twenty times larger than that for OA. This suggests that the hydroxybenzoic acid (HBA) moieties in the HA, such as GA, mainly contribute to the photoproduction of H2O2. The mechanism for the photoproduction of H2O2 was elucidated by the UV and NMR spectra of GA. Moreover, it was found by the spectroscopic parameters for the HBAs that the larger amounts of H2O2 were produced for the case of dihydroxyl and methoxyl groups.