Magnetic ferrous-doped graphene for improving Cr(VI) removal

A highly reductive and magnetic graphene/Fe3O4 composite (abbreviated as HR-M-GO/Fe3O4) was synthesized via graphene oxide (GO) oxidizing FeCl2 in situ. This superparamagnetic composite could be used for the highly efficient removal of Cr(VI) from waste water conveniently by applying an external magnet. The maximum adsorption capacity of the HR-M-GO/Fe3O4 for Cr(VI) reaches 31.8 mg g(-1), which is greater than the graphene/gamma-Fe2O3 composite. According to x-ray photoelectron spectroscopy (XPS), the possible mechanism of HR-M-GO/Fe3O4 removing Cr(VI) effectively was that Cr(VI) was reduced to Cr(III) by ferrous hydroxide moieties in the graphene structure and the resulting Cr(III) ions were easily captured by the negatively charged HR-M-GO/Fe3O4. In addition, such HR-M-GO/Fe3O4 with large surface area, negative charge and superior magnetism could be applied to remove Pb(II), Cu(II), and Zn(II) with an efficiency of almost 100%. This composite could therefore be used to remove trace Cr(VI), Pb(II), Cu(II), and Zn(II) from water for super purification.