Stepwise Synthesis of Graphene Oxide-Wrapped Magnetic Composite and Its Application for the Removal of Pb(II)

Graphene oxide-wrapped magnetic composite (GO-W-MC) with core–shell structure was prepared stepwise and characterized by scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectrometry, and vibrating sample magnetometer analysis. The preparation procedure included the following steps: synthesis of Fe 3 O 4 nanoparticles by a solvothermal method, surface coating of SiO 2 and – NH 2 groups, and encapsulation of GO sheets via covalent bonding. The key factors affecting the morphology and the structure of GO-W-MC have been analyzed in detail, and the related formation processes have been revealed. It was found that the concentration of the amination agent and the pH value of the GO solution have pronounced effects on the morphology and the structure of GO-W-MC. The GO-W-MC prepared at the optimized process conditions possesses a stable structure in which GO sheets are firmly grafted on the surface of the magnetic particles via covalent bonding and exhibits high magnetization (55 emu/g). The effects of pH on the adsorption and the adsorption isotherm were also studied. The results indicated that the adsorption capacity of GO-W-MC increases with the pH until a value of 7.0, and the GO-W-MC has a high adsorption capacity ( q m = 225.6 mg/g ) toward Pb(II) in aqueous solution, maintaining 80% adsorption capacity even after five adsorption–desorption cycles. This study could be of theoretical guidance for the synthesis of magnetic GO-based composites, with regard to optimization of process parameters, modification of structure, and performance enhancement.