Enhanced TiO2−x/peroxymonosulfate activation for atrazine photocatalytic degradation: regulation of surface/bulk oxygen vacancy

Efficient photocatalytic degradation of atrazine is a crucial method for enhancing the control of pesticide residues. In this study, a TiO 2−x nanotube (TNT) photocatalyst with surface/bulk oxygen vacancies (OVs) was fabricated via γ-ray irradiation reduction. Peroxymonosulfate (PMS) activation by surface/bulk OVs to accelerate the photocatalytic degradation atrazine (ATZ) was elucidated. Compare with no-radiation TNT (TNT-0), abundant OVs were distributed on the surface and bulk of TNT prepared via 56.5-kGy radiation reduction (TNT-56.5), which increased the hydroxyl oxygen content from 14.24 % to 33.66 %. Under visible light irradiation and PMS activation, the degradation kinetic constant of TNT-56.5 was 4.25-fold higher than that of TNT-0. Density functional theory calculations were performed to analyze the role of localized electrons of TNT-56.5 in PMS activation. Results showed that OVs were beneficial for the adsorption of ATZ and HSO 5 − . The oriented transfer of electrons from oxygen vacancy (OV) to PMS caused HSO 5 − heterolysis. Moreover, PMS activation by surface/bulk OVs synergistically produced radicals such as 1 O 2 , h + , •O 2 −, •OH, and •SO 4 − , which degraded ATZ; among these, 1 O 2 and h + were the core oxidizing species. The synergistic system (TNT-56.5/PMS/vis) exhibited broad pH adaptability and durable recyclability. This study presents direct evidence for surface/bulk OVs in enhancing PMS activation for the degradation of ATZ, providing a sustainable strategy for the degradation of pesticide residues.