A new catalyst material based on niobia/iron oxide composite on the oxidation of organic contaminants in water via heterogeneous Fenton mechanisms

The present work describes the preparation of novel materials based on niobia (Nb2O5)/iron oxides and their use as catalyst on oxidizing reactions of organic compounds in aqueous medium with hydrogen peroxide. These new composites were prepared by mixing natural niobia and iron oxides and were characterized with powder X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), and Fe-57 Mossbauer spectroscopy. Results showed that the main iron oxides so formed were goethite (alpha FeOOH) and maghemite (gamma Fe2O3) with small particle sizes. The decomposition study was realized with a basic dye as a model molecule: the methylene blue. The analysis of the products, with electrospray ionization mass spectrometry (ESI-MS), showed that the methylene blue was successively oxidized (hydrolyzed) through different intermediate species. These results strongly suggest that highly reactive hydroxyl radicals generated from the H2O2 on the surface of the 1:1 niobia:iron oxide composite act as an efficient heterogeneous Fenton catalyst (c) 2006 Elsevier B.V. All rights reserved.