摘要
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 °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 2 − reducing U(VI) to U(IV) first, followed by photoholes and • OH oxidizing U(IV) to insoluble U(VI) (UO 2 (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.
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