Amidoxime-Functionalized Magnetic Core–Shell Microspheres with Self-Assembled Antibacterial Ag Nanosheets for Enhanced Removal of Uranium

Efficient uranium adsorption and separation are crucial for advancing nuclear energy sustainably. Nevertheless, effective enrichment typically necessitates pristine conditions devoid of microorganisms (e.g., bacteria), thereby constraining the practical application of adsorbents. Silver (Ag) nanoparticle implant materials are considered as a viable solution where microorganisms cannot thrive. Here, the amidoxime (AO)-grafted magnetic core-shell adsorbent with antibacterial activity derived from the self-assembled Ag nanosheets around the bulk of Fe₃O₄@SiO₂ (denoted as Fe₃O₄@SiO₂@Ag nanosheets-AO) was developed. The Fe₃O₄@SiO₂@Ag nanosheets-AO exhibited an extraordinary affinity toward U(VI), with remarkable adsorption capacity (343.8 mg·g^-1) and high selectivity for U(VI). Extended X-ray absorption fine structure fitting results showed that the AO group and two H₂O molecules in Fe₃O₄@SiO₂@Ag nanosheets-AO are coordinated with uranyl ions to form a stable hexagonal bipyramidal geometrical configuration. The ease of magnetic separation meant that the loss of adsorbents was minimal, allowing for a sustained U(VI) removal efficiency of up to 90% even after 10 consecutive adsorption-desorption cycles. The presence of the Ag nanosheet shell in Fe₃O₄@SiO₂@Ag nanosheets-AO resulted in significant antibacterial properties targeting both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Overall, Fe₃O₄@SiO₂@Ag nanosheets-AO possess both antibacterial activity and abundant adsorption sites, making it excellent for uranium extraction and the purification of U(VI)-containing water.