Novel preparation of amidoxime functionalized hyper-cross-linked polymeric adsorbent on the efficient adsorption of uranium in aqueous solution

Herein, a series of novel amidoxime-functionalized porous polymeric adsorbents using dimethoxymethane (FDA) as the external cross-linker and biphenyl and amidoxime-functionalized 1-(benzyloxy)-4-ethylbenzene (BP-AO) as the original monomers were synthesized in one-pot Friedel-Crafts alkylation reactions via a simple “knitting” synthetic strategy. The adsorbents were characterized by FT-IR, solid-state 13C NMR/MAS spectrum, N2 adsorption-desorption, etc. The adsorption mechanism was probed by XPS, which suggests that the η2 complexation between uranium and amidoxime, and the polymers provide an approach to synthesize novel porous materials. The batch adsorption experiments showed that amidoxime hyper-crosslinked polymer-2 (HCPA-2) displays a uranium adsorption capacity of 27.7 mg/g at pH 6. The static adsorption action was more consistent with the Langmuir model and pseudo-second-order kinetics. Ionic competition experiments showed that Kd (U(IV)) is as high as 695.94 mL/g and reusable with a removal rate up to 60% after 7 cycles when 0.1 M HNO3 was used as a stripping agent, which verifies the practical application potential of the materials.