Efficient removal of trace uranium from nuclear effluents using irradiation-functionalized fibrous adsorbents with very high salt tolerance

The extraction of uranium from nuclear effluents is both conducive to the recycling of nuclear fuel and reduces environmental pollution. Adsorbents are widely regarded as the most promising materials for trace uranium extraction; however, the adsorption of trace uranium from high-salinity environments is a challenge for adsorbents used to recover uranium from nuclear effluents. In this study, four different irradiation-functionalized adsorbents were fabricated and evaluated to screen suitable adsorbents for the removal of trace uranium from nuclear effluents. We found that the adsorbent with synergistic adsorption groups (NWF-g-PGMA-AO) exhibited the most distinctive trace uranium removal efficiency and robust stability in acidic, alkaline, and high-salinity environments. It was the synergistic involvement of hydroxyls in the coordination of amidoximes with uranium that enhanced the binding energy of uranium to NWF-g-PGMA-AO, thus improving its performance. In addition, the residual uranium concentration decreased to the maximum allowable emission concentration of 50 ppb over a wide pH range, with a minimum concentration of 9.35 ppb. Interestingly, nitrate, sulfate, phosphate, and chloride anions in the effluents did not decrease the uranium removal efficiency, whereas fluoride considerably reduced the efficiency, and the removal ratio was negatively correlated with fluoride concentration. This is attributed to the formation of [UO2Fn]2-n (n = 1, 2, 3, 4) species, which exhibit a decreasing affinity for adsorbents with increasing fluorine atoms as revealed by density functional theory calculations. This work makes a stride in designing superior adsorbents with synergistic adsorption groups for extracting trace uranium from nuclear effluents.