Uranyl(VI) boosting 3D g-C3N4 photocatalytic H2O2 production for U(VI) immobilization

Uranium contamination derived from nuclear mining and nuclear waste has caused severe environmental and public health problems. Photocatalysis has been proved to be an available method for U(VI) elimination. However, photoinduced uranyl(VI) photocatalysis process tends to be overlooked. Herein, we reported that three-dimensional g-C3N4 boosted the production of photocatalytic H2O2 during recycling of U(VI). UO22+ was first excited to *UO22+ under visible light irradiation, then *UO22+ was further converted to UO2+ under organics, whereas UO2+ transferred into UO22+ and H2O2 was generated under the dissolving O2 condition (UO22+ → *UO22+ → UO2+ → UO22+). Meanwhile, massive H2O2 was produced from photogenerated electrons derived from the converting dissolving O2 on 3D g-C3N4 under visible light irradiation. The high-efficiency U(VI) immobilization was ascribed to the reaction of U(VI) and H2O2 to form uranyl peroxides (nano-metastudtite, UO2(O2)•2H2O, ∼20 nm width˟40 nm length). These observations give valuable insights into the photoinduced U(VI) immobilization in actual environment.