Degradation processes of organic compounds over UV-irradiated TiO2.: Effect of ozone

UV irradiation of TiO2 promotes electrons from the valence band to the conduction band. The capabilities of the resulting redox system to degrade organic pollutants in water and the variety of products formed is illustrated here by the case of 2,3-dimethylpyrazine. Two debated questions, viz. (i) which electron-donors are implicated to fill in the electron deficiencies in the valence band? and (ii) is superoxide chemically invovled in the photocatalytic degradations?, are addressed by using quinoline, the photo-Fenton reaction and superoxide dismutase. Finally, the favourable effect of ozone is exemplified by the photoctalytic removal of monochloroacetic acid.