Photocatalytic degradation of contaminants of concern with composite NF-TiO2 films under visible and solar light

Abstract

This study reports the synthesis and characterization of composite nitrogen and fluorine co-doped titanium dioxide (NF-TiO2) for the removal of contaminants of concern (COCs) in wastewater under visible and solar light. Monodisperse anatase TiO2 nanoparticles of different sizes and Evonik P25 were assembled to immobilized NF-TiO2 by direct incorporation into the sol-gel or by the layer-by-layer technique. The composite films were characterized with X-ray diffraction, high resolution-transmission electron microscopy, environmental scanning electron microscopy, and porosimetry analysis. The photocatalytic degradation of atrazine, carbamazepine, and caffeine was evaluated in a synthetic water solution and in an effluent from a hybrid biological concentrator reactor (BCR). Minor aggregation and improved distribution of monodisperse titania particles was obtained with NF-TiO2-monodisperse (10 and 50 nm) from the layer-by-layer technique than with NF-TiO2 + monodisperse TiO2 (300 nm) directly incorporated into the sol. The photocatalysts synthesized with the layer-by-layer method achieved significantly higher degradation rates in contrast with NF-TiO2-monodisperse titania (300 nm) and slightly faster values when compared with NF-TiO2-P25. Using NF-TiO2 layer-by-layer with monodisperse TiO2 (50 nm) under the solar light irradiation, the respective degradation rates in synthetic water and BCR effluent were 14.6 and 9.5·10-3 min-1 for caffeine, 12.5 and 9.0·10-3 min-1 for carbamazepine, and 10.9 and 5.8·10-3 min-1 for atrazine. These results suggest that the layer-by-layer technique is a promising method for the synthesis of composite TiO2-based films compared to the direct addition of nanoparticles into the sol.