Synthesis of acid-resistant phenanthroline-skeleton polymers applicable to the PUREX process and exploration of their U(VI) adsorption mechanism.

To achieve selective U(VI) separation from highly acidic PUREX (plutonium uranium reduction extraction process) waste liquors, an acid-stable phenanthroline-functionalized polymer (DAPhen-P) was fabricated via utilizing the excellent acid-resistant coordination performance of phenanthroline-diamide ligands. Owing to the synergistic chelation of dual functional sites, DAPhen-P achieves excellent uranium (VI) capture performance, with a maximum adsorption capacity of 452.35 mg/g at pH 6.0. Benefiting from phenanthroline diamide moiety, the material retains a high uranium uptake capacity of 91.00 mg/g even in 4.0 M HNO₃, simulating harsh working conditions of nuclear fuel reprocessing. Two contrast adsorbents (DPy-P and DB-P) were further fabricated to elucidate the correlation of structure and performance. The as-prepared DAPhen-P exhibits outstanding structural stability, with intact framework and adsorption performance after long-term immersion in 4.0 M HNO₃ solution or electron beam irradiation at a total dose of 600 kGy. In high-salinity aqueous systems with a Na/U molar ratio of 2957:1, uranium removal rate of DAPhen-P exceeds 98%, presenting prominent anti-interference capability toward common metal cations and lanthanide ions. For simulated low-concentration uranium wastewater (50 μg/L), the uranium removal efficiency remains above 97%. Additionally, a favorable adsorption capacity of 44.52 mg/g is obtained for uranium-spiked real seawater (15 mg/L U).