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Marine biofouling is one of the most significant challenges hindering practical uranium extraction from seawater. Single atoms have been widely used in catalytic applications because of their remarkable redox property, implying that the single atom is highly capable of catalyzing the generation of reactive oxygen species (ROS) and acts as an anti‐biofouling substance for controlling biofouling. In this study, the Co single atom loaded polyacrylamidoxime (PAO) material, PAO‐Co, is fabricated based on the binding ability of the amidoxime group to uranyl and cobalt ions. Nitrogen and oxygen atoms from the amidoxime group stabilize the Co single atom. The fabricated PAO‐Co exhibits a broad range of antimicrobial activity against diverse marine microorganisms by producing ROS, with an inhibition rate up to 93.4%. The present study is the first to apply the single atom for controlling biofouling. The adsorbent achieves an ultrahigh uranium adsorption capacity of 9.7 mg g−1 in biofouling‐containing natural seawater, which decreased only by 11% compared with that in biofouling‐removed natural seawater. These findings indicate that applying single atoms would be a promising strategy for designing biofouling‐resistant adsorbents for uranium extraction from seawater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic-single-molecular material is used for uranium adsorption for the first time. • Fully exposure of functional group guarantees high uranium adsorption capacity. • The magnetism of the adsorbent endows it with high recyclability and reusability. • High adsorption capacity of 84.31 mg/g is achieved in simulated nuclear wastewater. • Highest uranium adsorption speed is achieved in simulated nuclear wastewater. Highly efficient treatment of uranium contamination is of great importance for the sustainable development of the environment. The recovery of uranium by adsorbents is a feasible strategy for treating uranium contamination. However, due to insufficient exposure of the contact interfaces, currently available adsorbents usually take extremely long time for uranium adsorption. Herein, a magnetic-single-molecular amidoxime adsorbent M−AO−Fc is fabricated for highly efficient recovery of uranium from nuclear wastewater by endowing the amidoximated cyanoferrocene with magnetism. The adsorbent M−AO−Fc shows a maximum uranium adsorption capacity of 510.60 mg/g in uranium solution. In an acidic simulated nuclear wastewater containing a large number of interfering ions, M−AO−Fc also shows a high uranium adsorption capacity of 84.31 mg/g within a short equilibrium time of 60 min. The full dispersion of M−AO−Fc and full exposure of functional groups are the critical reasons for the excellent uranium adsorption performance. Attributing to the magnetism of M−AO−Fc, this adsorbent can be efficiently recovered by magnetic recovery and shows high reusability. This study proves that the magnetic-single-molecule would be a promising adsorbent for uranium recovery and opens up a new direction for designing a uranium adsorbent. [ABSTRACT FROM AUTHOR]

• A new double-network hydrogel is explored for uranium recovery from seawater. • U-adsorption capacity of the hydrogel is greatly enhanced by added nanoclay. • Mechanical property of the hydrogel is largely improved by th double-network. • Used materials are lowcost and the hydrogel owns good U-adsorption reusability. Massive uranium recovery from seawater is a key project to provide the long-time consumption of global nuclear power, while it is still greatly difficult to achieve high-efficient adsorbents with high mechanical property. In this work, a new nanoclay-poly(amidoxime) (NC-PAO) high-strength double-network (DN) composite hydrogel adsorbent with high-efficient and fast uranium extraction capacity has been explored. The uranium adsorbing performance can be significantly enhanced by the small content of added super-hydrophilic NC (Laponite RDS sheets), because of the largely improved hydrophilicity of the hydrogel. Compared with the blank PAO DN hydrogel without nanoclay, the uranium adsorbing capacity of this NC-PAO DN hydrogel can largely increase 73.4% from 4.97 mg/g to 8.62 mg/g, after in seawater only 25 days. The uranium adsorption rate of this hydrogel from natural seawater, can reached 0.345 mg/(g∙day), which is excellent among existing uranium adsorbents. Furthermore, this hydrogel has high mechanical performance with 2.42 MPa of tensile strength and 16.13 MPa of compressive strength, which can be used in seawater for relatively longer time than traditional low-strength single-network hydrogel, owing to its double network (DN) structure (the weakly crosslinked gelatin soft network and the strongly crosslinked cellulose nanofiber (CNF) hard network). This NC-PAO DN hydrogel adsorbent will be an excellent candidate for fast uranium recovery from seawater in largescale. Most importantly, this work will inspire the development of new hydrogel-based adsorbents and even other type of adsorbents for high-efficient uranium extraction, through compositing various low-cost and super-hydrophilic nanomaterials to significantly improve the hydrophilicity of the adsorbent and designing double-network structure to largely enhance the mechanical property. [ABSTRACT FROM AUTHOR]