Selective, rapid extraction of uranium from aqueous solution by porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite and differential charge calculation

Herein, a new porous chitosan–phosphorylated chitosan–amidoxime macroporous resin composite (PCAR) was designed and synthesized for the rapid and selective extraction of uranium resources from aqueous solution. This study showed that PCAR exhibited excellent adsorption toward uranium in a pH range of 5–9. The dynamic adsorption process aligned with the quasi-second-order kinetic model and corresponded to the chemical adsorption process. The maximum adsorption capacity was 561.28 mg·g−1 at pH 6 and 308 K. Mechanism analysis showed that the synergistic effect of the amidoxime group (−(NH2)C=N–OH), PO, and –NH2 on the PCAR surface improved the uranium adsorption performance. The differential charge density indicated that the amidoxime and phosphate groups provide lone-pair electrons for the adsorption of UO22+ and their synergistic effect improves the UO22+ adsorption performance of PCAR. The uranium distribution coefficients of PCAR and CAR are 4.6 and 2.4 times those of vanadium, respectively. These results indicate that phosphorylation can ameliorate the disadvantage of competitive vanadium adsorption of the amidoxime adsorbent. In addition, PCAR exhibits good reusability and stable adsorption capacity after five adsorption–desorption cycles. Hence, PCAR has excellent potential for uranium extraction from aqueous solution.