Nanostructured vanadium-doped iron oxide: catalytic oxidation of methylene blue dye

Abstract

V-doped iron oxides are used as heterogeneous catalysts to oxidize the dye methylene blue in an aqueous medium containing hydrogen peroxide. XRD and Mössbauer spectroscopy reveal that vanadium is incorporated into the iron oxide structure. The H₂O₂ pretreatment of the solid catalyst promotes important surface and structural changes in the iron oxides primarily due to the formation of peroxo-vanadium complexes, which specifically enhance the catalytic properties of the material. Transmission electron microscope images show that the H₂O₂ treatment also tends to decrease the mean particle size of the material grains. V-doped iron oxides were found to play an important role as solid catalysts in H₂O₂ reactions. The prepared vanadium containing iron oxide was confirmed to exhibit remarkable catalytic activity for the oxidation of methylene blue, an important contaminant from textile industry. In fact, the ESI-MS spectrum obtained for methylene blue after reaction with the V-doped oxide shows hydroxylation by hydroxyl radicals in solution forming species with m/z = 130 and m/z = 110.