Enhanced radical production and electronic-structure modulation for photocatalytic phosphorus mineralization of tributyl phosphate using Al-doped TiO2

Al-doping induced lattice distortion and structural defects in the TiO 2 shell. • Fe 3 O 4 imparts magnetic recoverability to the TiO 2 -Al photocatalyst. • 77.8% phosphorus mineralization of TnBP was achieved under UV irradiation. • DFT calculations reveal the engineered electronic structure boosts radical kinetics. • Photocatalytic treatment progressively reduced the biological inhibitory effect. Tributyl phosphate, a representative organophosphorus ester, is environmentally persistent due to its refractory nature, leading to widespread concern over its residue. Photocatalysis employing titanium dioxide (TiO 2 ) is a commonly studied method for degrading such pollutants, yet conventional TiO 2 systems are hindered by the high cost of requisite precious-metal cocatalysts, difficulties in recovering ultrafine catalyst powders, and rapid electron-hole recombination. To address these limitations, a TiO 2 -Al@Fe 3 O 4 photocatalyst was synthesized in this work via a sol-gel method, in which Al 3+ was doped into the TiO 2 lattice. This Al 3+ incorporation induced lattice distortion and created structural defects. The substitution of Ti 4+ by Al 3+ introduces charge imbalances and localized strain, which are key to forming active defect sites that subsequently modify the electronic structure. The modified catalyst exhibits a narrowed bandgap and an engineered surface structure that collectively further promote the generation of reactive oxygen species. Consequently, the TiO 2 -Al@Fe 3 O 4 /UV process achieved 77.8% phosphorus mineralization of tributyl phosphate within 10 h using a low photocatalyst dosage of 0.3 g/L. Furthermore, toxicity analysis indicated that most of the transformed products have lower predicted toxicity than the original parent compound. These results demonstrate that the TiO 2 -Al@Fe 3 O 4 composite functions as a magnetically recoverable and active photocatalyst, providing an effective strategy for the phosphorus mineralization of recalcitrant organophosphorus compounds. Download: Download high-res image (270KB) Download: Download full-size image