Recyclable graphene oxide-covalently encapsulated magnetic composite for highly efficient Pb(II) removal

A graphene oxide-wrapped Fe3O4 magnetic composite (GO-W-MC) was prepared by grafting GO sheets on the modified surface of Fe3O4 via covalent bonding, and used as magnetic adsorbent to remove Pb(II) ions. The composite was characterized by SEM/TEM, XRD, FTIR, XPS, and VSM. The characterization results indicate that the covalent bond involving GO and Fe3O4 was formed between the oxygen groups from GO and the functional groups from the modified Fe3O4 surface. The obtained GO-W-MC consisted of silica-functionalized Fe3O4 nanoparticles (∼200 nm in diameter) completely encapsulated by silky-like crumpled GO sheets, and dispersed well in aqueous solution. The effect of pH on adsorption, adsorption isotherm, adsorption kinetics, and regeneration were investigated. The results indicate that the adsorption capacity of GO-W-MC increased until pH 7, and that the adsorption process was well fitted by the Langmuir isotherm and the pseudo-second-order kinetic model. The as-prepared GO-W-MC had a high adsorption (qm = 253.2 mg g−1) and could maintain 80% adsorption capacity even after ten adsorption-desorption cycles, indicating that it could be recyclable. Hence, the high capacity and excellent regenerability of GO-W-MC favor its use as adsorbent, which can accelerate the practical application of GO based composites in environmental remediation.