Highly efficient removal of U(VI) by the photoreduction of SnO2/CdCO3/CdS nanocomposite under visible light irradiation

Reducing soluble U(VI) to insoluble U(IV) is an ideal strategy to collect/remove uranium in water. In this work, a new way is reported to achieve this reduction through a photocorrosion-related photocatalysis process of SnO2/CdCO3/CdS (SCC) under visible light irradiation. The mechanism is systematically studied and discussed through a variety of characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Mott-Schottky test, etc. The matching of energy band ensures the separation of photoelectrons and holes, which results in the decrease of charges' recombination rate and the enhancement of photoreduction activity. The reduction process can be efficiently performed in the ternary complex of SCC in that the photo-generated holes are consumed by oxidization of S2- to S-0 on CdS in SCC. Furthermore, uranium extraction could be achieved by SCC without any protective gases or electronic sacrificial agent, which shows great advantages in applications of U(VI) collection/removal.