Synergy of pyrophosphate and unsaturated nitrogen sites for efficient uranium recovery from concentrated nitric acid.

Efficient recovery of uranium from spent nuclear fuel (SNF) reprocessing in ultra-acidic and radiation-intensive environments is critical for sustainable uranium resources management. However, traditional extractants exhibit instability and reduced uranium adsorption capacity under such harsh conditions. Here, we present a metal-free pyrophosphate-incorporated g-C₃N₄ polymer (PCNx) featuring unsaturated nitrogen sites and pyrophosphate groups for robust uranyl ion coordination. The inherent stability of g-C3N4 endows PCNx with high resistance to concentrated 12 M HNO3 and 500 kGy radiation. The optimal PCN1/3 achieves an uranium adsorption capacity of 75.3 mg g-1 in 12 M HNO3 and a high removal efficiency of 79.1% in a mixed ion solution, with a high distribution coefficient (Kd) of 18,964 mL g-1. This study demonstrates a promising proof-of-concept for designing functional polymers that efficiently recovers uranium from ultra-acidic and radiation-intensive conditions during SNF reprocessing.