Ultra-Fast One-Minute Photocatalytic Degradation of Methylene Blue Using Mixed-Phase TiO2 Nanopowder: High Efficiency and Reusability

This study investigates the ultra-fast photocatalytic degradation of methylene blue (MB) using a mixed-phase titanium dioxide (TiO2) nanopowder synthesized via a sol-gel method followed by dehydration and calcination at 450 °C for 2 h. The resulting TiO2 exhibits a biphasic structure composed of 87.4% anatase and 12.6% brookite, confirmed by X-ray diffraction (XRD), Rietveld refinement, and high-resolution transmission electron microscopy (HR-TEM). TEM analysis reveals the nanoparticles are predominantly spherical with an average particle size of 18.5 nm and a standard deviation of 4.6 nm. Under UV light irradiation at 366 nm, the synergistic interaction between the two crystalline phases enhances charge separation and facilitates rapid generation of reactive oxygen species (ROS), enabling complete MB degradation within 1 min, the fastest rate reported so far for mixed-phase TiO2. Notably, the nanopowder exhibits high operational reusability, retaining its photocatalytic performance for at least 30 consecutive cycles with persistent degradation efficiency in each cycle. These results highlight the critical role of phase composition and nanostructure optimization in the design of TiO2 photocatalysts for robust and sustainable environmental remediation, particularly in dye-polluted water treatment.