A Membrane-Supported Bifunctional Poly(amidoxime-ethyleneimine) Network for Enhanced Uranium Extraction from Seawater and Wastewater

Uranium extraction from natural seawater and wastewater are quintessential requirements to supply uninterrupted carbon-free nuclear energy and to prevent potential radiochemical and toxicological effects, respectively. Owing to the complexity and low-concentration uranium of these water samples, the design and synthesis of sorbent materials for uranium extraction with meaningful efficiencies remains a grand challenge. Herein, we reported a novel three-dimensional bifunctional network of hyperbranched poly(amidoxime-ethyleneimine) (PAO-h-PEI) using PEI as the skeleton material via cyanoethylation, crosslinking and then amidoximation. As a result of the synergistic supramolecular strategy, the PAO-h-PEI membrane achieved a remarkable adsorption capacity of 985.7 mg/g for aqueous uranium solution, which was 2.5 folds that of the monofunctional h-PEI membrane (387.6 mg/g). The PAO-h-PEI membrane also exhibited good selectivity towards uranium in the presence of various metal ions, high-content salt, and natural organic matter as well as common anions. According to the XPS and FTIR results, the utilization of amines as the second ligand enhanced uranyl binding by providing additional coordination sites or by interacting with oxime to force N-OH dissociation. The good reusability (adsorption rate of 93% after six adsorption-desorption cycles) and satisfactory adsorption performance in extracting low-concentration uranium in real seawater demonstrate its practicability.