Spray pyrolysis synthesis and UV-driven photocatalytic activity of mesoporous Al2O3@TiO2 microspheres

Mesoporous microspheres of Al2O3@TiO2 were effe ctively and rapidly prepared by the sol-spray pyrolysis (SP) method. Ultrasonic-induced droplets containing titania sol, boehmite sol, and citric acid (CA) were pyrolyzed to γ-Al2O3-incorporated anatase TiO2 microspheres. The SP-derived Al2O3@TiO2 microspheres exhibited higher porosity and lower bandgap energy than pure TiO2 and commercial P25. The TiO2 microspheres incorporated with 5 wt% amorphous γ-Al2O3 efficiently removed tetracycline (TC) after 60 min of pre-adsorption and 140 minutes of UV illumination (removal efficiency ~ 91%, surpassing those of pure TiO2 and commercial P25). Introducing amorphous γ-Al2O3 into the anatase TiO2 matrix created a synergetic effect that enhanced the accumulation of TC onto the catalyst surface; meanwhile, the formation of defective heterojunctions favored the separation and immigration of the photo-generated holes and electrons. In a reaction mechanism analysis, h+ and O2•‾ radicals were identified as the main instigators of TC photooxidation. Furthermore, the SP-derived Al2O3@TiO2 microspheres demonstrated good stability and renewability in durability tests. The study provides a simple and scalable method for manufacturing Al2O3-decorated TiO2 microspheres with improved adsorption and photocatalytic performance.