Nano-ZnO enhanced amidoxime-functionalized sodium alginate composite hydrogel microspheres for uranium capture from wastewater

Effective removal of uranium from wastewater is of vital significance for the human health and environmental protection. In this paper, by adopting the use of co-mingling and covalent cross-linking methods, nano-ZnO enhanced the amidoxime-functional sodium alginate composite hydrogel (SA/CMC-ZnONPS-AO1) was prepared. The mechanical stability of SA/CMC-ZnONPS-AO1 was improved with the assistance of ZnO. The introduction of amidoxime group effectively improved the selectivity of uranyl ions (KdU = 10016 mL/g). The fitted maximum adsorption capacity of SA/CMC-ZnONPS-AO1 for U(VI) was 641.7 mg/g at 298 K and pH = 4. This is higher than most of sodium alginate-based adsorbents which were currently used for uranium removal from wastewater. Furthermore, in the dynamic adsorption column experiment at the scale of the laboratory, the adsorption equilibrium (163 mg/g) was acquired after 3 days in a low-concentration uranium solution (50 mg/L). Finally, the possible adsorption mechanism was discussed. This study not only provides a new method for the preparation of adsorption agents, but also provides theoretical support for the actual application of adsorbents in the uranium-containing wastewater.