Biochar decorated 2D/2D heterojunction with enhanced photocatalytic activity for uranium extraction

The acquisition of resources and treatment of pollution associated with uranium are of profound significance for the long-term sustainability of nuclear power. Photocatalytic technology offers a promising strategy for uranium extraction due to its ability to enhance the reaction kinetics and selectivity. However, developing photocatalysts with high-efficiency charge separation remains a significant challenge in uranium extraction. Herein, we devised and prepared a biochar decorated 2D/2D heterojunction, Bi2WO6/g-C3N4/BC, for uranium extraction from seawater and wastewater. Due to the layered structure and matched lattice of Bi2WO6 and g-C3N4 nanosheets, Bi2WO6/g-C3N4 heterojunction can be easily fabricated, providing a large interface contact area and excellent charge transfer. The synergistic effect of biochar with the heterojunction further enhances light adsorption and promotes the separation of photogenerated electron-hole pairs. These features endow the Bi2WO6/g-C3N4/BC composite with a suitable bandgap and effective electronic conductivity for photocatalysis of uranium. The photocatalytic product was identified as the air-stabilized metastudtite (UO2)O2 center dot 2H2O, which is formed by photogenerated e- and center dot O2- during the photocatalysis process. As a result, Bi2WO6/g-C3N4/BC achieves a uranium capacity of 3.2 mg g- 1 in natural seawater within 7 days and a uranium removal rate of 85.9 % in simulated nuclear wastewater. This study provides novel insights into the fabrication of highly efficient electronic conduction for uranium photocatalysts, which is significant for accelerating the development of uranium resource recovery and pollution treatment.