Advanced oxidation processes: mechanistic aspects

The reactive intermediate in Advanced Oxidation Processes (AOPs) is the *OH radical. It may be generated by various approaches such as the Fenton reaction (Fe2+/H2O2), photo-Fenton reaction (Fe3+/H2O2/hnu), UV/H2O2, peroxone reaction (O3/H2O2), O3/UV, O3/activated carbon, O3/dissolved organic carbon (DOC) of water matrix, ionizing radiation, vacuum UV, and ultrasound. The underlying reactions and *OH formation efficiencies are discussed. The key reactions of *OH radicals also addressed in this review.