In water treatment using AOPs, oxidative dissolution of organic pollutants in wastewater is achieved using hydroxyl (radical dotOH) radicals generated using a combination of ozone, ultraviolet (UV) light, a semiconductor photocatalyst, hydrogen peroxide, ultrasound, and a Fenton reagent [7]. The oxidation–reduction potential of radical dotOH radicals is 2.85 eV, which is high compared with those of ozone (2.07 eV), hydrogen peroxide (1.77 eV), and hypochlorous acid (1.49 eV) [8]. Therefore, radical dotOH radicals are highly reactive and it is theoretically possible to use them to decompose almost all organic compounds to inorganic materials, such as water and carbon dioxide. Moreover, radical dotOH radicals cannot exist for a long time under the normal environment and becomes extinct after generation. Therefore, it is not required secondary treatment [9].