Synthesis of Naphthalimidedioxime Ligand-Containing Fibers for Uranium Adsorption from Seawater

A novel ligand-functionalized adsorbent material was prepared using a combination of radiation-induced graft polymerization (RIGP) and click chemistry (1,3 cycloaddition reaction). The design of the ligand-containing amidoxime functionality is based on its chelating efficiency with uranium. In this process, RIGP is used to graft polymer chains on fiber substrates, where the fibers are prepared by irradiating and treating polyethylene (PE) with different bulk ratios of vinyl benzyl chloride and acrylic acid or itaconic acid. Furthermore, chemical modifications of these fibers are performed using a two-step process, where novel bisimidoxime ligands are incorporated into fibers. These ligands contain imidedioxime, which is known to be a uranophile. Also, the core structure of the ligand containing three donor atoms facilitates the formation of chelate with uranyl ion in media such as seawater. Density functional theory calculations were performed to quantify the binding strength with the uranyl ion. When tested with simulated seawater with a uranium concentration of 6 ppm at pH 8.0-8.3, the developed materials showed moderate to high uranium (similar to 35-50 g U/kg adsorbent) adsorption capacity.