Synthesis of a porous amidoxime modified hypercrosslinked benzil polymer and efficient uranium extraction from water

Benzil was hypercrosslinked to produce a novel hypercrosslinked porous organic polymer skeleton (HCP-CO) with an ultrahigh Brunauer-Emmett-Teller (BET) surface area of 605.4 m2·g−1. The skeleton was grafted with diaminomaleonitrile (DAMN) via a simple Schiff base reaction, and then reacted with hydroxylamine hydrochloride (NH2OH·HCl) to produce an amidoxime-modified hypercrosslinked benzil polymer (HCP-AO) possessing many amidoxime groups. The chelation of the amidoxime group and uranium (VI) and porous structure provided HCP-AO with excellent adsorption performance. The maximum adsorption capacity for the uranium of HCP-AO can reach 370.9 mg·g−1 at pH = 6. Moreover, the adsorption process agreed well with the Langmuir and pseudo-second-order models, thus indicating it was monolayer chemical adsorption. HCP-AO demonstrated excellent selectivity and recyclability; furthermore, the removal rate for uranium still remained at 66.35% in the coexistence of metal ions in simulated seawater. Furthermore, after five adsorption–desorption cycles, the adsorption capacity of HCP-AO slightly reduced. To summarize, we synthesized an efficient adsorbent that possesses high adsorption capacity, selectivity, and recyclability; it has good potential for uranium extraction from water.