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Abstract: In this work materials based on iron oxide dispersed over activated carbon were prepared and tested in the H2O2 decomposition and removal of the methylene blue (MB) model from aqueous solution. Two different supports were evaluated: a commercial activated carbon (CAC) and an activated carbon produced by coffee used grounds (ACK). These materials, after iron impregnation (CAC/Fe and ACK/Fe), were characterized using XRD, SEM, N2-sorption, XPS and Mössbauer spectroscopy. The main results suggest the formation of composites with high surface area and iron dispersion containing Fe3+ on the surface of both catalysts. Catalytic tests revealed high capacity for H2O2 decomposition by both composites with more activity for ACK/Fe. MB removal experiments showed intense removal of the model through combined adsorption and oxidation processes. The detection of known MB oxidation intermediates observed by ESI-MS studies confirmed the occurrence of MB oxidation processes and also showed more activity for ACK/Fe. [Copyright &y& Elsevier]

Abstract: 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 57Fe Mössbauer spectroscopy. Results showed that the main iron oxides so formed were goethite (αFeOOH) and maghemite (γFe2O3) 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 [Copyright &y& Elsevier]