Highly effective photocatalytic extraction of rhenium by bronze-phase TiO2 from aqueous solution after uranium mining

Rhenium (Re), as a high-value metal, plays a significant role in many strategic fields, but not has independent mineral sources worldwide and mainly exists as an associated with other mineral resources. The associated rhenium in uranium (U) ore is of great concern. Herein, we propose a novel photocatalytic strategy to extract rhenium from mixed waste liquid after uranium mining. A typical bronze phase TiO2(B) photocatalyst was prepared by a simple hydrothermal treatment method, and were characterized by various spectroscopic techniques. The special energy band and morphology of TiO2(B) facilitate the photogenerated carrier separation and transfer. The photocatalytic performance of the material for Re(VII) in the absence or presence of U(VI) was investigated. The results indicate that under the irradiation of simulated sunlight, TiO2(B) can completely extract rhenium from the rhenium/uranium mixed waste liquid with a concentration of 0.1–1 mg L−1 Re(VII) at pH = 0, and then sequentially extract U(VI) (10 mg L−1) at pH = 5 through adsorption and photocatalysis. After photocatalytic reaction, soluble Re(VII) was reduced to Re(VI), and then disproportionated to insoluble Re(IV). Compared with the reported photocatalysts, the photocatalytic Re(VII) reduction on TiO2(B) was directly achieved only by photogenerated electrons. The advantage of TiO2(B) lies in its wider bandgap and more negative conduction band potential, which makes the extraction of rhenium from aqueous solution through a feasible and green photocatalytic pathway.