Effect of Bi2WO6 nanoflowers on the U(VI) removal from water: Roles of adsorption and photoreduction

The efficient, safe, low-cost and easy to treatment of uranium(U(VI))-containing wastewater is still an imminent problem. Herein, the hierarchical hollow-spherical bismuth tungstate (Bi2WO6) was prepared by hydrothermal method, and sufficiently characterized by morphology and photoelectrochemical properties. In this research, we not only discussed the adsorption performance of U(VI), but also investigated the photocatalytic reduction performance of U(VI), so as to provide technical support for the treatment of U(VI)-containing wastewater in the future. The adsorption procedure complied with the pseudo-second-order model, implying surface complexation or chemisorption. Besides, under visible-light irradiation lasting for 600 min, the photoreduction removal rate of U(VI) was 53% (just adding 2.0 mg Bi2WO6), without adding the h+ scavenger, due to the harvest absorption of solar energy, hierarchically porous structure and synergic effect of adsorption and photocatalysis. Furthermore, the adsorption mechanism and photocatalytic reduction mechanism of Bi2WO6 for U(VI) were revealed. The metal 3O and O3H bonds in Bi2WO6 crystal were the active coordination sites for U(VI) adsorption, while •O2− and e- were the main active species for U(VI) photocatalytic reduction. Although the mechanisms of adsorption and photocatalytic reactions were different, there was a synergistic effect in the process of practical for application removing U(VI) by Bi2WO6. Consequently, the hierarchical nanosheets-assembled Bi2WO6 microspheres could be considered as a good candidate for visible-light-responsive photocatalyst in radioactive wastewater treatment.