Magnetic metal-organic frameworks (Fe3O4@ZIF-8) composites for U(VI) and Eu(III) elimination: simultaneously achieve favorable stability and functionality

The water stable core-shell microspheres (Fe3O4@ZIF-8) with strong magnetism were successfully fabricated through a facile modification strategy. Concrete procedures included firstly pretreatment of Fe3O4 core with anionic polyelectrolyte to acquire negatively charged Fe3O4 particle surface, followed by nucleation through attracting Zn2+ cation, and then growth of a thin layer of ZIF-8 (~25 nm). Various characterization techniques (SEM, TEM, FT-IR, XRD, VSM, BET and XPS) indicated that the Fe3O4@ZIF-8 microspheres were highly stable and magnetic with a large specific surface area (606.91 m2/g) and fairly sufficient functional groups (NH, OH, COOH, ZnO, NO and CN). Multi-factors affecting the radionuclides removal performance on Fe3O4@ZIF-8 was adequately explored, comprising contact time, temperature, pH, ionic strength, co-existing ions and extreme conditions. And the results showed that Fe3O4@ZIF-8 exhibited fast reaction kinetics (~30 min to achieve equilibrium), excellent uptake capabilities (539.7 mg U/g and 255.6 mg Eu/g), remarkable selectivity and favorable physicochemical stability. These researches suggested that Fe3O4@ZIF-8 could not only simultaneously achieve favorable stability and functionality, but also easily to be separated by external magnetic field after used in radioactive sewage treatment, which was of considerable practical utility in extracting radioactive wastes though in harsh circumstance.