Ultrafast Synthesis of MOF-Derived Magnetic Ni@C Catalyst for Efficient Photo-Enhanced Uranium Recovery in Real Nuclear Wastewater

Photocatalytic reduction of uranium from wastewater containing high concentrations of fluoride is crucial from both environmental and sustainability perspectives. However, the coordination of fluorine and uranyl ions to U(VI)-F complexes with high bond strengths poses challenges for photocatalysts. Electrostatic interactions induced by photocatalysis to dissociate U(VI)-F complexes provide an effective method for the extraction of uranium from wastewater containing fluorine. Herein, we report the preparation of a magnetic Ni nanoparticle-anchored metal carbon composite heterojunction catalyst, Ni@C-700, via ultrafast Joule heating of nickel-based metal-organic frameworks (MOFs) for photoassisted uranium extraction. Owing to the synergistic effects of the plasmon effect, electrostatic attraction, and host-guest interaction, Ni@C-700 exhibits a high extraction efficiency of 93.9% and a reduction ratio of 84.1% to U(VI) within 120 min at 100 mg/L U(VI) in simulated fluoride-containing wastewater without a sacrificial agent. Additionally, Ni@C-700 demonstrates excellent ion selectivity and reusability. In real nuclear wastewater, Ni@C-700 exhibits an extraction capacity of 1628.4 mg/g within 120 min and is efficiently recovered through an external magnetic field. The mechanism study demonstrates that uranium was captured through the formation of a stable 2O_ax-1U-3O_eq configuration, which was achieved via photoassisted separation of uranium and fluorine. This study offers an efficient method for uranium recovery from nuclear industry wastewater.