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

Abstract

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.

Keywords: Adsorption; Mesoporous Al2O3@TiO2; Microsphere; Photocatalysis; Spray pyrolysis.