Efficient extraction of uranium from seawater by reticular polyamidoxime-functionalized oriented holocellulose bundles

A novel multi-layered reticular polyamidoxime (PAO)-functionalized holocellulose bundles (ML-r-PAO@HB) with abundant oriented micro-channels and high mechanical strength was created via a facile solvent-exchange strategy and used for the first time to capture uranium from seawater. Due to the hydrophobic interaction of PAO chains induced by the solvent-exchange, multi-layered reticular PAO was successfully self-assembled onto the oriented micro-channels of the HB, which greatly improved the accessibility to the adsorption sites by increasing the exposed surface of PAO. The ML-r-PAO@HB exhibited high uptake capacity (851.42 mg g-1 PAO) and excellent adsorptive selectivity for U(VI) ions. After exposure to 500-L natural seawater for 28 days, an ultra-high uranium extraction capacity (9.74 mg g-1 PAO) was achieved by ML-r-PAO@HB. The N and O atoms in the -C(NH2)N-OH group were the main coordination sites for U(VI) uptake. These wonderful performances render the ML-r-PAO@HB highly desirable for the large-scale uranium extraction from seawater.