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 (PCN_x) featuring unsaturated nitrogen sites and pyrophosphate groups for robust uranyl ion coordination. The inherent stability of g-C₃N₄ endows PCN_x with high resistance to concentrated 12 M HNO₃ and 500 kGy radiation. The optimal PCN_1/3 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 (K_d) 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.