Designing flexible TiO2/SrTiO3/BiOBr recyclable fiber membrane with spatial dual oxidation sites for photocatalytic uranium extraction under visible light

Abstract

The utilization of nuclear energy generates a substantial volume of wastewater containing uranium, posing a significant threat to both aquatic ecosystems and human health. The current photocatalytic materials utilized for uranium extraction commonly exhibit insufficient redox capabilities, inefficient separation of photogenerated carriers, and challenging recovery. Therefore, recyclable TiO₂/SrTiO₃/BiOBr (TSB) dual Z-scheme heterojunction fiber membrane materials with dual oxidation sites were successfully synthesized, with advantages of rapid carrier separation and transfer and a broad photo-response range of the dual Z-scheme heterojunctions. Due to the presence of dual oxidation sites, TSB exhibited an exceptional uranium extraction performance, achieving a remarkable 98.9 % extraction rate without the need for sacrificial agents, which was 2.48, 1.79, and 3.34 times of those of ordinary TiO₂, SrTiO₃, and BiOBr, respectively. The extraction rate of uranium from TSB was 85 % after five cycles. Optical and photoelectric tests revealed that TSB reduced the bandgap width by 0.25 eV compared to that of TiO₂, enhanced the fluorescence lifetime by 1.3 ns, lowered the electrical resistance, and higher optical current density, confirming the effective charge transport at the catalyst interfaces. The charge transfer routes in the TSB dual Z-scheme were confirmed by X-ray photoelectron spectroscopy and density functional theory. The potent oxidizing ·OH generated by TSB played a crucial role in facilitating the conversion of U(VI) into insoluble (UO₂)O₂·2H₂O. In conclusion, this work provides a novel strategy for the design of dual Z-scheme heterojunctions and offers a new method for practical and recoverable uranium extraction.