Preparation of Magnetic Composite Photocatalysts and Their Application in Uranium Extraction from Seawater

Uranium is the basic and key resource for the development of nuclear energy, but the existing land uranium reserves are relatively limited, and the sustainable supply of uranium resources faces major challenges. The new method of uranium extraction from seawater can provide important technical reserve for realizing the diversification of uranium resources and guaranteeing the sustainable development of nuclear energy. Among the approaches of uranium extraction from seawater, photocatalysis has become a research hotspot in recent years, attributed to its low pollution, low energy consumption and high recovery rate. This project focused on the preparation of high efficiency photocatalysts and its photocatalytic performance. Among the photocatalysts that have been studied, graphitic carbon nitride (g-C3N4) photocatalyst is relatively cheap and stable, and considered to be an ideal photocatalyst. Titanium dioxide (TiO2) photocatalyst can effectively reduce hexavalent uranium to tetravalent uranium in radioactive wastewater. Bismuth vanadate (BiVO4) also presents remarkable potential in photocatalytic reduction of uranium. In this paper, g-C3N4 was obtained by hydrothermal method with urea and ammonium chloride as raw materials calcined at 500°C for 3 hours. TiO2 was mixed with g-C3N4, reacted at 160°C for 4 hours, dried and cooled, and then ground to obtain TiO2/g-C3N4. The obtained material was added to the prepared Fe3O4@NiSiO3 sample, heated in a water bath at 70℃ until sol appeared, and the dried solid powder was calcined in a Muffle furnace at 500℃ for 3 h. After cooling, the magnetic composite photocatalyst sample was obtained by grinding. Magnetic BiVO4/g-C3N4 composites can be prepared by a similar method. The magnetic function optimizes the control of the catalyst in solution. The uranium in seawater was catalyzed by the two composite photocatalysts in an automatic photocatalytic device, and the concentration of uranium in the solution was reduced to 76% and 75% of the original concentration respectively under the condition of ultraviolet light. The results indicated that these two composite photocatalysts can be used for the extraction of uranium from seawater and the methods are expected to provide a new path for the development of uranium resources.