Graphene oxide/ferroferric oxide/polyethylenimine nanocomposites for Congo red adsorption from water.

Graphene oxide/ferroferric oxide/polyethylenimine (GO/FeO/PEI) nanocomposites were synthesized by an in situ growth of FeO nanoparticles on GO sheets, and then modified by PEI. The GO/FeO/PEI nanocomposites showed extremely high removal efficiency for anionic dye Congo Red (CR) due to the positively charged PEI molecules (methylene blue was also tested but with low adsorption capacity due to its cationic property). The CR removal capacity was 574.7 mg g, higher than most of reported results. The adsorption kinetics could be well described by a pseudo-second-order model. Furthermore, GO/FeO/PEI nanocomposites could be easily recycled by magnetic separation. The removal efficiency remained above 70% after five cycles.