Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe0/Fe3O4 composites is described. The composites with several Fe0/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe0 and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron Mössbauer surface characterization of the composites Fe0/Fe3O4, Fe0, Fe3O4, α-Fe2O3 and γ-Fe2O3 suggested that Fesurf2+ species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO radicals generated from Fesurf2+ species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe0 is discussed in terms of a creation of Fesurf2+ species during the preparation of the composite and by an electron transfer mechanism from Fe0 to Fesurf3+ during the Fenton reaction to regenerate the Fesurf2+ active species.