Synthesis of crystalline carbon nitride with molten salt thermal treatment for efficient photocatalytic reduction and removal of U(VI)

It is critical to recover uranium from wastewater containing U(VI) and to ensure the commercial development of nuclear-related energy sources. The extraction and recovery methods of uranyl ions from contaminated areas have become clearer with the rapid development of photocatalytic technology. However, there are several challenges, such as low-charge carrier migration and a lack of active sites. Crystallized carbon nitride (CCN) catalysts at different temperatures were successfully obtained to improve the efficiency of photocatalytic reduction of uranium. The characterization results show that the crystallinity of the material increased and improved the electron–hole separation efficiency. We investigated the effects of catalyst dosage, pH value of a solution, and concentration of U(VI) on the photocatalytic reactions as well as the photoreduction mechanisms. The efficiency of photocatalytic reduction of uranium is enhanced by 2.5 times with good stability in five cycles compared with bulk carbon nitride. The results demonstrate that CCN can effectively remove U(VI) by photocatalytic reduction, which has a wide range of applications prospects in the treatment of uranium-containing wastewater.