Magnetic metal-organic framework (Fe3O4@ZIF-8) core-shell composite for the efficient removal of Pb(II) and Cu(II) from water

In this work, Fe3O4@ZIF-8 core-shell magnetic composite was synthesized by a solvothermal method and used to remove Pb2+ and Cu2+ from wastewater. Various characterization techniques (SEM, TEM, XRD, BET, VSM, and TGA) indicated that the Fe3O4@ZIF-8 microspheres were stable and had a high specific surface area (724.7 m2/g). The factors that affected the performance of Fe3O4@ZIF-8 during the removal of Pb2+ and Cu2+ from wastewater are discussed, including the adsorbent amount, pH, temperature, contact time, concentration, ionic strength, and coexisting ions. Moreover, the adsorption processes were well described by the Langmuir model, and the uptake capacities of Fe3O4@ZIF-8 were calculated to be 719.42 mg/g for Pb2+ and 301.33 mg/g for Cu2+. In addition, Fe3O4@ZIF-8 also had fast adsorption kinetics for the uptake of Pb2+ and Cu2+ from wastewater, and it only took 20 min and 60 min to reach adsorption equilibrium, respectively. More importantly, the material could be reused at least four times. The mechanism study showed that ion-exchange and coordination reactions were the main Pb2+ and Cu2+ removal mechanisms of Fe3O4@ZIF-8. Thus, the synthesized Fe3O4@ZIF-8 composite is a promising candidate material for removing Pb2+ and Cu2+ from wastewater.