Porous and Biofouling-Resistant Amidoxime-Based Hybrid Hydrogel with Excellent Interfacial Compatibility for High-Performance Recovery of Uranium from Seawater

Abstract

For a massive uranium recovery from seawater, designing an adsorbent with ultrahigh uranium uptake capacity and good biofouling-resistant activity is crucial, but difficult. Here, a facile and eco-friendly freeze-thawing strategy was explored for the first time to create a physically crosslinked poly(amidoxime) (PAO)-chitosan (CS) hybrid hydrogel (PAO@CHM) with excellent interfacial compatibility, superior uranium uptake capacity and good antibiofouling activity. The porous 3D network architecture of PAO@CHM, combined with its good hydrophilicity as well as antibacterial properties, synergistically constructs numerous hydrophilic and biofouling-resistant ion channels for the rapid diffusion of uranyl ions into the interior of the hydrogel, achieving maximum use of adsorption active sites on PAO@CHM. Consequently, superior uranium uptake capacities (743.87, 865.27, and 1091.53 mg g^-1 for PAO fixed on hydrogel) were obtained in 8, 16, and 32 ppm U-spiked water, respectively. Benifiting from the enhanced uranium adsorption activity and good antibacterial properties, the uranium extraction capacity of PAO@CHM reached 7.46 mg g^-1 after 28 days of exposure in 500 L of natural seawater, which is significantly higher than most adsorbents. The O and N atoms in amidoxime group act as main bonding sites for uranium uptake. The finding of this study provides a facile and eco-friendly strategy to construct hydrophilic and biofouling-resistant amidoxime-based adsorbent for efficient uranium recovery from seawater.

Keywords: Uranium recovery, Amidoxime, Freeze-thawing, Hydrogel, Anti-biofouling