Photocatalytic oxidation mechanism of benzonitrile in aqueous suspensions of titanium dioxide

The photocatalytic oxidation of benzonitrile was carried out in aqueous suspensions (pH 11) of commercial polycrystalline TiO2 (Merck and Degussa P25) irradiated by ultraviolet light. The rate of decomposition was dependent on the concentration of benzonitrile and followed a pseudo-first order kinetics. The complete mineralization of a 0.70 mM benzonitrile solution was achieved in ca. 8 h by using TiO2 Degussa P25, whereas the substrate was only partially mineralized even after 14 h of irradiation in the presence of TiO2 Merck. The final oxidation products were carbonate and nitrate. The appearance and the evolution of organic and inorganic intermediate species were also investigated and allowed to hypothesize the reaction pathways.