Natural and H2-reduced limonite for organic oxidation by a Fenton-like system: Mechanism study via ESI-MS and theoretical calculations

A Fenton-like system based on iron oxide surface modification by thermal treatment under H2 flow was investigated. The materials were characterized by powder X-ray diffraction (XRD), chemical analyses, scanning electron microscopy (SEM), temperature programmed reduction (TPR) and 57Fe Mössbauer spectroscopy. Results showed that the main iron oxides phases in the thermal treated material were goethite (α-FeOOH) and magnetite (Fe3O4). A decomposition study was carried out using a basic dye as a model compound (methylene blue). The reactions were monitored by electrospray ionization mass spectrometry (ESI-MS), revealing that the methylene blue dye was successively oxidized (hydroxylations) forming different intermediaries species. These results strongly suggest that highly reactive hydroxyl radicals generated from the reaction of H2O2 on the catalysts surface were responsible for the dye oxidation, proving that the material act as an efficient heterogeneous Fenton-like catalyst. Theoretical quantum mechanics calculations, DFT, were carried out in order to understand the degradation mechanism for methylene blue with goethite.

In this work the reactivity of the Fenton heterogeneous system HCOOC//H2O2 using thermal treated limonite was studied. Experiments were carried out to investigate the effect of formic acid contents and Fe2+ sites in iron oxide applied to the methylene blue dye oxidation, using a Fenton-like heterogeneous and intermediates formation monitored by ESI-MS.Figure optionsDownload as PowerPoint slide