Visible light driven Ti3+ self-doped TiO2 for adsorption-photocatalysis of aqueous U(VI).

The photocatalytic reduction of U(VI) is recognized as an economical and effective way for U(VI) removal/recovery from solutions. To improve the photocatalytic activity of TiO2 under visible light, TiO2 was hydrogenated by NaBH4 to generate Ti3+ self-doped black TiO2 (BTn). The self-doped Ti3+ alongside oxygen vacancies (Ov) could act as interband level to increase visible light capture and reduce the recombination of photogenerated carriers. The obtained BTn samples showed high performance for U(VI) elimination under near neutral conditions, and held an outstanding anti-interference for U(VI) over competing metal cations and anions. Methanol and ethanol could act as sacrificial donors, being favorable for the photocatalytic reduction of U(VI), while the presence of EDTA inhibited the photoreduction of U(VI). The BTn photocatalysts showed relatively high stability and reusability during the photocatalysis and elution processes. The XPS, TEM and XRD results revealed that U(VI) was photo-reduced to form UO2 on the surface of BTn. This work may serve as an important reference for improving the photocatalytic reactivity of TiO2 as well as for the efficient removal/recovery of U(VI) from aqueous solutions.