The electrolysis-graded leaching process for rapid resource regeneration of Th(IV)/U(VI) from wastewater

Uranium and thorium are strategic metals, and the mining and utilization of uranium and thorium produce a large amount of radioactive wastewater. In this paper, a new process combining electrolysis and leaching is proposed to achieve resource regeneration of uranium and thorium from radioactive wastewater. The results revealed that carbonate was the optimal separation system. The uranium-thorium separation was based on the formation of soluble UO2(CO3)34− and insoluble ThO2. And the separation efficiency was determined to reach a maximum value of 4.8 × 104 at pH 10.5. Surprisingly, UO2(CO3)34− could be effectively electrochemically recovered, and more than 90% of uranium could be recovered within 3 h, which indicated that uranium could be efficiently recovered. In addition, U–Th leaching studies were performed, and the results showed that selective leaching of uranium could be achieved at 0.01 M, while effective leaching of Th could be achieved at 0.3 M, thus establishing a graded-leaching process for U–Th. To reduce the impact of Ba2+ on the uranium electrochemical separation process, the SO42--CO32- combined system was developed, and the concentration of Ba2+ was reduced by two orders of magnitude. The final result revealed that the purity had been roughly tripled via this process. This study provides an effective strategy to reduce the waste of non-renewable uranium-thorium resources and process wastewater, achieving the recycling of non-renewable resources and the sustainable development of nuclear energy.