Preparation of amidoxime modified covalent organic framework for efficient adsorption of lead ions in aqueous solution

Lead ion is one of the most common heavy metal contaminants for human health. Therefore, it is necessary to develop the efficient and selective adsorbents to remove lead ions in wastewater. Here, an amidoximated covalent organic framework was designed as adsorbent (COF-NHOH) for the removal of lead ions from aqueous solutions. The adsorption properties were studied by batch adsorption. The adsorption process is quickly completed in just 30 min. The highest adsorption capacity of the COF-NHOH is 368.68 mg/g at 298 K, which is much higher than that of JUC-500. Kinetic, isotherm and thermodynamic results show that the adsorption process is a spontaneous monolayer chemical adsorption process. The adsorbent removes selectively lead ions from a complex multi-ion environment. Moreover, the adsorption ability of the adsorbent decreased by only 14.05 % after five cycle experiments. COF-NHOH exhibits excellent anti-interference ability and reusability. Finally, COF-NHOH achieves efficient removal of lead ions through chelation and electrostatic action based on DFT calculations and others. In conclusion, the adsorbent showed excellent application for the removal of lead ions from aqueous solutions.