Construction of magnetic COF composites for lead removal with fast dynamics and superior capacity

The removal of heavy metals is very important because of their nonbiodegradability and toxicity to the general population and environment. Adsorption is regarded as a promising approach for target pollutant removal due to its simplicity and economy. Novel magnetic covalent organic framework (COF) composites (Fe3O4@TpPa-NO2) consisting of a magnetic Fe3O4 core and a TpPa-NO2 COF shell are synthesized and developed as adsorbents for Pb(II) removal from aqueous solution. The obtained composites exhibit superior adsorption performance (909.1 mg/g) and fast adsorption dynamics (adsorption equilibration time of less than 10 min) toward Pb(II). The experimental data for the adsorption of Pb(II) follow pseudo-second-order kinetic and Langmuir isotherm models. The superior performance of Fe3O4@TpPa-NO2 for Pb(II) elimination is attributed to electrostatic and coordination interactions between the metal ion and functional groups (nitrogen and oxygen) of magnetic COF composites. The Pb(II)-loaded Fe3O4@TpPa-NO2 can be easily regenerated by acid treatment. Furthermore, Fe3O4@TpPa-NO2 demonstrates excellent reusability and maintains a high removal efficiency throughout five consecutive adsorption-desorption processes. Various COF-based magnetic adsorbents can be fabricated for specific pollutants due to the diversity in the structure and pore size of the COFs, which present attractive prospects for high-efficiency removal of contaminants in water treatment.