Preparation of hollow B-SiO2@TiO2 composites and their photocatalytic performances for degradation of ammonia-nitrogen and green algae in aqueous solution

Abstract Hollow B–SiO 2 @TiO 2 composites were prepared by the wet chemical deposition method starting from TiCl 4 and hollow B–SiO 2 microspheres. TiO 2 layers composed of anatase TiO 2 nanoparticles were coated on the surfaces of the hollow B–SiO 2 microspheres probably through the formation of Ti O Si and Ti O B bonds. A great number of OH groups were also present at the TiO 2 coating layers. The presence of Ti O Si bonds and Ti O B bonds resulted in the formation of defects in the TiO 2 coating layers, which decreased the band gap of the TiO 2 coating layers to ca. 3.0 eV and endowed the TiO 2 coating layers with visible light absorption performance. The buoyancy hollow B–SiO 2 @TiO 2 composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae. The conversion of ammonia-nitrogen reached 65% when the degradation of ammonia-nitrogen (43 mg·L −1 at pH value of 8) was catalyzed by the B–SiO 2 @TiO 2 (100:10) composite under the simulated solar light irradiation at 35 °C for 660 min. The green algae (5 mg·L −1 ) were almost completely degraded over the B–SiO@TiO 2 (100:20) photocatalyst under the visible light irradiation at 35 °C for 510 min.