Visible light photocatalytic degradation of tetracycline over TiO2

TiO2 is widely exploited as a photocatalyst to degrade antibiotic residues in water under UV irradiation, but it is inefficient for visible light photocatalysis due to its large band gap. Herein, it is the first time to report the photodegradation of tetracycline (TC) over TiO2 under visible light irradiation. 25.1% of removal efficiency for TC was achieved even under 700 nm light irradiation. Furthermore, it was demonstrated that O2− species, which were generated from photoexciting of a surface complex between TC molecules and TiO2, played a critical role in the visible light photocatalytic degradation of TC. In addition, it was found that the visible light photocatalytic degradation generated different active species and intermediate products from those under UV irradiation. N-doped TiO2 exhibited even better performance for visible-light photocatalytic degradation of TC with higher removal efficiency and larger mineralization rate, which followed different degradation-mechanism.