Green Nanocellulose/PEI‐Grafted Magnetic Nanoparticles for Effective Removal of Heavy Metal Ions

In response to the pressing issue of water pollution caused by heavy metal ions, there is a growing demand for green adsorbents that can effectively remove these contaminants while being easy to separate and regenerate. A novel magnetic composite was synthesized by bonding amino-functionalized Fe3 O4 -SiO2 magnetic particles (MNP-NH2 ) to polyethyleneimine (PEI)-grafted cellulose nanofibers (CNF). The modification of CNF with PEI through a peptidic coupling reaction resulted in the uniform dispersion and strong attachment of MNP-NH2 particles (286.7 nm) onto the PEI-CNF surface. This composite exhibited exceptional adsorption capabilities for heavy metals, achieving 16.73 mg/g for Pb, 16.12 mg/g for Cu, and 12.53 mg/g for Co. These remarkable adsorption capacities are attributed to the complex interactions between the metal ions and the amino, carboxyl, and hydroxyl groups on the surface of PEI-CNF-MNP. The introduction of PEI significantly enhanced the adsorption capacities, and the adsorption sequence (Pb(II)>Cu(II)>Co(II)) can be explained by differences in ionic radius and surface complexation strength. Langmuir isotherm and pseudo-second-order kinetic models described the adsorption process, while Na2 EDTA was proved effective for desorption with high recovery rates. This magnetic composite holds promise for treating heavy metal-contaminated wastewater due to its impressive performance.