Rapid Magnetic Separation Absorbent Integrating Amidoxime Chelators and Antibiofouling MOF Coatings for Efficient Uranium Extraction

Developing adsorbents that couple high uranium affinity with durability in complex environments remains a pivotal challenge for efficient uranium harvesting. Here, we report a hierarchically engineered magnetic composite, Fe3O4@PAO@MPN-Met, that integrates (i) a superparamagnetic Fe3O4 core for rapid separation, (ii) an amidoxime-rich polyamidoxime (PAO) shell for uranyl chelation, (iii) a bioinspired metal-polyphenol network (MPN) adhesive layer, and (iv) an in situ mineralized Cu2+/d-methionine (d-Met) metal-organic framework (MOF) that imparts long-lasting antibiofouling activity. Stepwise solvothermal synthesis, surface grafting, and self-assembly preserve nanoscale morphology while reducing the saturation magnetization only to 16.4 emu/g─still sufficient for 1 min magnetic separation. Under optimal conditions, the material achieves a maximum uranium uptake of 272 mg/g, fitting the Langmuir model and quasi-second-order kinetics, indicative mainly of monolayer chemisorption controlled. Thermodynamic analysis reveals a spontaneous, endothermic, and entropy-driven process. The composite shows outstanding selectivity, with uranyl distribution coefficients at least 2 orders of magnitude higher than those of competing ions. After five adsorption-desorption cycles using 0.1 M HNO3, 80% of the initial capacity is retained. Crucially, the Cu-Met nanochannels confer broad-spectrum antibacterial performance, suppressing Pseudomonas aeruginosa formation by 98.54%. In natural Bohai Sea water, after 7 days of adsorption, the uranium adsorption capacity is 0.322 mg/g, highlighting its salt tolerance and antifouling resilience. This multifunctional design, marrying strong amidoxime chelation, magnetic recoverability, and MOF-mediated antibacterial action, offers a viable route toward selective, reusable, and biofouling-resistant adsorbents for large-scale uranium harvesting from seawater.