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

Graphene oxide/ferroferric oxide/polyethylenimine (GO/Fe₃O₄/PEI) nanocomposites were synthesized by an in situ growth of Fe₃O₄ nanoparticles on GO sheets, and then modified by PEI. The GO/Fe₃O₄/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^-1, higher than most of reported results. The adsorption kinetics could be well described by a pseudo-second-order model. Furthermore, GO/Fe₃O₄/PEI nanocomposites could be easily recycled by magnetic separation. The removal efficiency remained above 70% after five cycles.