Efficient cooperative extraction uranium(VI) from aqueous solution and seawater by a novel phosphate/amidoxime chitosan-based adsorbent

Herein, a novel chitosan-based porous adsorbent (CS-AO-AMP) with multifunctional efficient cooperation groups, such as amidoxime and phosphate groups, was synthesized to enhance U(VI) sorption. The optimal pH for U(VI) sorption is 7–9, which is beneficial for extraction U(VI) from seawater. The maximum U(VI) sorption of CS-AO-AMP is up to 620 mg/g at 298 K and pH 8.0. In simulated seawater, the salts of high concentration, such as Na3PO4, NaCl, NaClO4 and Na2SO4, have little influence on U(VI) sorption capacity. Whereas in 0.1 M Na2CO3 solution, the uranium sorption capacity is only 13.5 mg/g. The selective sorption capacity of U(VI) can reach 72.9 mg/g in five mixed-metal solutions. After one week static sorption in 100 mL natural seawater, the U(VI) sorption capacity can reach 266.6 μg/g. After four sorption-desorption cycles, CS-AO-AMP shows excellent recovery performance and maintains 90 % of the initial sorption capacity. The sorption process follows pseudo-second-order kinetic model, Langmuir, Sips and Freundlich isotherm models, indicating that sorption is dominated by chemisorption, together with monolayer and multilayer sorption. All in all, the CS-AO-AMP has a very high application prospect of extracting U(VI) from aqueous solution and seawater.