Mechanism for the seleikctive adsorption of uranium from seawater using carboxymethyl-enhanced polysaccharide-based amidoxime adsorbent

Land-based uranium resources are becoming scarce because of the widespread development and use of nuclear energy. Therefore, to make up for the shortage of uranium resources, a new chitosan/carboxymethyl-β-cyclodextrin/quaternary ammonium salt-functionalized amidoxime carbon adsorbent (CSAOCF) was designed and synthesized for extracting uranium from seawater. Experimental studies show that the adsorption of uranium by CSAOCF is a spontaneous endothermic reaction and chemical adsorption. The theoretical maximum adsorption capacity of uranium can reach 726 mg/g at 308 K and pH = 6. Moreover, the adsorption efficiency and selectivity of CSAOCF for uranium were significantly improved after the introduction of the carboxymethyl group, and the selection and partition coefficient of CSAOCF for uranium and vanadium increased from 16-fold to 30-fold under the same conditions. This indicates that there is a synergistic effect between carboxyl and amidoxime groups, which can promote the adsorption of uranium by CSAOCF. Furthermore, CSAOCF exhibits good oil resistance and can be reused more than five times. Therefore, CSAOCF containing carboxymethyl and amidoxime functional groups can considerably improve the selective adsorption of uranium and has great potential in the extraction of uranium from seawater.