Amidoxime-functionalized zeolitic imidazolate frameworks with antimicrobial property for the removal of U (VI) from wastewater

Abstract

The removal of U (VI) from wastewater is an arduous technological task wherein biofouling caused by microorganisms severely depletes the relevant properties of adsorbents. Herein, the zeolitic imidazole frameworks dubbed ZIF-90 were functionalized with amidoxime via the production of a diaminomaleonitrile intermediate to manufacture a highly efficient U (VI)-adsorbing material with antibacterial properties called amidoxime-appended ZIF-90 (ZIF-90-A). The crystal and pore structures of ZIF-90 and its modified materials were characterized by FT-IR, XRD, SEM, XPS and BET. ZIF-90-A has a superior uranium-uptake capacity (490.2 mg/g) at pH 5, which is close to the pH of wastewater. At the same time, ZIF-90-A also exhibited outstanding antimicrobial properties. Values for the minimum inhibitory concentration (MIC) of ZIF-90-A were measured to be 125 and 250 μg/mL against Staphylococcus aureus and Escherichia coli, respectively. In addition, ZIF-90-A displayed good selectivity for the adsorption of UO22+; moreover, the uranium-uptake capacity of ZIF-90-A did not exhibit an obvious reduction when the adsorbent was subjected to five adsorption–desorption cycles. These results suggest that ZIF-90-A is a viable choice for the efficient removal of U (VI) from nuclear wastewater.