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[Display omitted] • Directional dendritic gels were constructed via the binder-regulated freeze casting. • The directional channels accelerated the water permeation rate. • The hierarchical structures enhanced the surface area and supplied more adsorption sites. • The mechanical strength was improved due to the support of dendritic networks. • The uranium capture rate reached 0.21 mg g−1 day−1 in the natural seawater. Directional microchannels can speed up the transportation of seawater in adsorbents, and the introduction of nanopores in the microchannels can enhance the specific surface area and endow the adsorbent with more adsorption sites, which are beneficial for improving the uranium adsorption ability. Herein, directional dendritic and hierarchical porous aerogels (DDH-PAO gels) were constructed by the binder-regulated freeze casting. The gels displayed directional dendritic channels and special honeycomb-like nanopores, which endowed the DDH-PAO gels with a rapid water permeation rate (0.74 s) and a large BET area. They exhibited good uranium adsorption capacities of 494.34 mg-U/g-Ads (in 16 ppm U-spiked simulated seawater) and 6.3 mg-U/g-Ads (in nonspiked natural seawater). The adsorption process can be observed by the naked eyes due to significant color changes before and after uranium adsorption. The uranium adsorption mechanism was analyzed by kinetic models and XPS spectra, and the role of regulators in microstructures formation was investigated by changing the amount of PVA. The directional microchannels, honeycomb-like nanopores, rapid water transportation rate, and high mechanical strength indicated that the DDH-PAO gels are promising for real uranium extraction from seawater. [ABSTRACT FROM AUTHOR]

• A new strategy of cooperative reaming is used to prepare macroporous hydrogel. • The pore size on the novel MP-PAO hydrogel membrane reaches up to 40 µm. • The MP-PAO membrane shows both high uranium sorption capacity and good reusability. • The high adsorption rate can be gained with 24-day extraction equilibrium time. As nuclear power plant fuel, nearly 4.5 billion tons of uranium is reserved in the ocean with a low concentration of 3.3 ppb. Uranium capture from natural seawater relies heavily on the development of highly efficient uranium adsorbent. By combination of the water-soluble pore-forming agent (sodium bicarbonate, NaHCO 3) and alkali treatment technology, a novel macroporous polyamidoxime (MP-PAO) hydrogel membrane is prepared for highly efficient uranium sorption. The macropores with a size of about 40 µm in diameter contribute to the exposure of previously hidden coordination bond sites and fast diffusion of uranyl ion. As a result, the MP-PAO membrane adsorbent delivers superior uranium sorption capacity of 5.80 mg-U/g-Ads, almost 1.76 times that of the pristine polyamidoxime (PAO) membrane adsorbent. Strikingly, the adsorption equilibrium of uranium on the MP-PAO membrane can be reached within 24 days. The adsorption rate of MP-PAO membrane is 14.29% faster than that of the reference PAO membrane. In addition, the MP-PAO membrane also shows a good reusability and long service life. The strategy applied in this work is widely suitable for the preparation of macroporous adsorbents. MP-PAO membrane holds tremendous potential for uranium capture from natural 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]