Decomposition of 3-chlorophenol on nitrogen modified TiO2 photocatalysts

Highlights: ► N-modified TiO2 for 3-chlorophenol degradation under UV and Vis light. ► Improvement of TiO2/N photoactivity with an increase of calcination temperature. ► Improvement of 3-chlorophenol photodegradation rate with pH increase from 3 to 7. ► Stable photocatalytic activity of N-modified photocatalysts in repeated cycles. - Abstract: Photocatalytic activity of nitrogen modified TiO2 calcined at temperatures of 100–350 °C toward 3-chlorophenol (3-CP) degradation was studied. In the experiments the fluorescent UV lamp and the incandescent lamp emitting mainly Vis light were applied. The degradation efficiency was evaluated on a basis of changes of 3-CP, total organic carbon and Cl− concentration. A significant improvement of the photoactivity of the N-modified photocatalysts compared to the reference sample was observed. The rate of 3-CP degradation increased with the calcination temperature, and the highest efficiency was achieved for TiO2 annealed at 350 °C. After 5 h of UV irradiation in the presence of TiO2/N-350 and reference TiO2 the 3-CP concentration decreased for 77% and 36%, respectively. The 3-CP removal after 24 h of Vis irradiation was 30% and 12% for the N-modified and reference samples, respectively. The 3-CP decomposition and mineralization were greatly influenced by pH of the solution, achieving the highest rate at pH 7 for the modified photocatalysts. An increase of the calcination temperature resulted in an increase of the rate of ·OH formation. The photocatalytic activity of the N-modified TiO2 remained unchanged during repeated photocatalytic degradation cycles.