The elimination of Sulfaclozine in the three systems: UV/TiO2, UV/K2S2O8, and UV/TiO2/K2S2O8. Sulfaclozine is weakly adsorbed on the surface of TiO2 at pH 7 (< 5%) but efficiently eliminated with the following three systems: UV/TiO2, UV/K2S2O8, and UV/TiO2/K2S2O8 in ultra pure water. Moreover, 12 of Sulfaclozine by-products are identified and reaction pathways show that, in addition of OH and SO4 radicals, the conduction-band electrons are responsible for the formation of some main by-products either directly or by the formation of superoxide radicals.