Phosphorylation improved the competitive U/V adsorption on chitosan-based adsorbent containing amidoxime for rapid uranium extraction from seawater.

A novel chitosan-based porous composite adsorbent with multifunctional groups, such as phosphoric acid, amidoxime, and quaternary ammonium groups, was prepared to improve the adsorption rate and competitive uranium‑vanadium adsorption of amidoxime group adsorbents. The maximum uranium adsorption capacity of PACNC was 962.226 mg g at 308 K and pH = 7. The maximum adsorption rate constant of PACNC for uranium was 2.83E-2 g mg min, which is 2.38 times that of ACNC (1.19E-2 g mg min). Moreover, the adsorption equilibrium time was shortened from 300 (ACNC) to 50 (PACNC) min. In simulated and real seawater, the K and adsorption capacity of PACNC for uranium were approximately 8 and 6.62 times those for vanadium, respectively. These results suggest that phosphorylation significantly improved the competitive adsorption of uranium‑vanadium and uranium adsorption rate. PACNC also exhibited good recycling performance and maintained stable adsorption capacity after five cycles. DFT calculations were used to analyze and calculate the possible co-complex structure of PACNC and uranium. The binding structure of phosphate and amidoxime is the most stable, and its synergistic effect effectively improves the competitive adsorption of uranium-vanadium of amidoxime. All the results demonstrated that PACNC has substantial application potential for uranium extraction from seawater.