Visible-light-driven photoextraction of uranyl by O-doped hexagonal-cubic CdS phase heterojunction

Photocatalytic U(VI) extraction is considered as the most promising way to solve the current shortage of uranium resources and radioactive contamination. In this work, O-doped hexagonal-cubic CdS phase heterojunction was constructed by a simple thermal treatment and was successfully used for the photoextraction of U(VI) from water bodies. The samples with different heat treatment temperatures have different phase ratios and oxygen doping amounts. The experimental results show that the CdS heat treated at 350 degrees C (CdS-350) has the best photocatalytic activity, which can extract 80% of uranium within 120 min (m/v(CdS-350) = 0.4 mg/g, C-U(VI) = 50 ppm). More interestingly, a systematic mechanistic investigation shows that the extraction process is divided into two steps: i.e., photoelectrons and O-center dot(2)- reducing U(VI) to U(IV) first, followed by photoholes and (OH)-O-center dot oxidizing U(IV) to insoluble U(VI) (UO2(OH)(2)). The second step of oxidation allows CdS-350 to avoid photocorrosion, resulting in an excellent recycling performance of only 8% decrease in performance after four cycles.

Automated summary

Photocatalytic U(VI) extraction using O-doped hexagonal-cubic CdS phase heterojunction is an effective method for extracting uranium from water bodies, with CdS-350 showing the best photocatalytic activity. The extraction process involves two steps: photoelectrons reducing U(VI) to U(IV) and photoholes oxidizing U(IV) to insoluble U(VI). CdS-350 demonstrates good recycling performance with only 8% decrease in performance after four cycles.