IMPACT OF LIGAND SELECTION ON EFFECTIVENESS OF MODIFIED PHOTO- FENTON PROCESSES

摘要

Fenton's reagent is only effective under acidic conditions (pH 2-4) with the inactivity of Fenton's reagent at higher pH usually attributed to the formation of ferric oxyhydroxide floes and precipitates. The formation of ferric oxyhydroxides can be prevented by adding Fe(Ⅲ) chelators. Like degradation using Fenton's reagent, the degradation of compounds by chelated iron and H_2O_2 can be accelerated by irradiation with UV or UV-visible light. Some Fe(Ⅲ) complexes (such as those involving oxalate or citrate ligands) are unreactive in the dark but become active when irradiated. This enhancement is due to the photolysis of Fe(Ⅲ) complexes. Fe(Ⅲ) is reduced by a photo-induced ligand-to-metal charge transfer reaction and the resulting Fe(Ⅱ) reacts with H_2O_2 to generate hydroxyl radicals.