Effect of oxygen-containing functional groups on the adsorption of cationic dye by magnetic graphene nanosheets

Since its high stability, large specific surface area, honeycomb structure, high recovery and reproducibility, magnetic graphene has become a research hotspot in recent years. Batch equilibrium experiments of methylene blue (MB) were conducted on magnetic graphene nanosheets (Fe3O4@GNs) and magnetic graphene oxide (Fe3O4@GO) to probe effect of oxygen-containing functional groups (OFGs) on the potential active centers and adsorption mechanism of the cationic dyes. The microstructure and morphology of the magnetic graphene-based materials were characterized by X-ray diffraction spectra (XRD), Fourier transform infrared spectra (FTIR) and Scanning electron microscopy (SEM) technologies. Owing to the OFGs attenuation, Fe3O4@GNs presented a very high maximum monolayer MB adsorption capacity of 211.34 mg g−1 at 318 K and can be recycled easily by an external magnet. The kinetic results prove that the adsorption rate of MB mainly controlled by a chemical-sorption involving π-π force through sharing and electrons exchange between Fe3O4@GNs and MB molecular. It indicates that the enhanced hydrophobic and the strong π-π interaction can be influenced from the disappearing of CO functional groups. This group may be responsible for the attractive performance of Fe3O4@GNs. In addition, SEM results confirm that the role of Fe3O4 nanoparticles is not only can effectively prevent the aggregation of GNs but also be beneficial to improving the adsorption ability.