The direct photolysis of hydrogen peroxide leads to the formation of .OH radicals:
H2O2 ---->2.OH (in the presence of UV)
Also HO2– , which is in an acid–base equilibrium with H2O2, absorbs the UV radiation of the wavelength 254 nm:
H2O2 ---->O2– + H+
HO2– ---->.OH + O–
H2O2/UV process has been successfully used for the destruction of chlorophenols and other chlorinated compounds. Molecules of atrazine, desethylatrazine, and simazine can be mineralized finally to carbon dioxide within reasonable irradiation times in the presence of hydrogen peroxide. H2O2/UV can also be used for water disinfection purposes.