Evidence for the Active Species Involved in the Photodegradation Process of Methyl Orange on TiO₂

Active species such as holes, electrons, hydroxyl radicals (•OH), and superoxide radicals (O 2 •– ) involved in the photodegradation process of methyl orange (MO) over TiO 2 photocatalyst were detected by several techniques. Using different types of active species scavengers, the results showed that the MO oxidation was driven mainly by the participation of O 2 •–, holes and •OH radicals. Characterized by the liquid chromatography/mass spectrometry, the transversion of the degradation products with the light irradiation time was first analyzed. Combined with the measurement of oxidation reduction potential, dissolved oxygen, conductivity, and pH values, the degradation process of MO on TiO 2 under the effect of the active species was revealed. This was the first time that electrodes were introduced to track the degradation process in situ, and these parameters would be helpful to explain the degradation processes of other organic pollutants.