Formation of hydroxyl radicals by α-Fe2O3 microcrystals and its role in photodegradation of 2,4-dinitrophenol and lipid peroxidation

Abstract

α-Fe2O3 microcrystals were produced for application as catalyst in different oxidation processes in both chemical and biological matrices. Hematite was produced by sol–gel method in situ with silica matrix and characterized by X-ray diffraction analysis, scanning electron microscopy with energy-dispersive X-ray spectrometry, and transmission electron microscopy. The ability of the catalyst to produce hydroxyl radicals (·OH) was evaluated by electron paramagnetic resonance measurements using 5,5-dimethyl- 1-pyrroline-N-oxide (DMPO) as spin trap. Characterization of the resulting DMPO-OH adduct established that α-Fe2O3 microcrystals could generate ·OH when Fenton chemistry was present. Additionally, the catalyst exhibited semiconducting properties, as the DMPO-OH signal was produced under visible-light irradiation in presence of O2 but without requiring H2O2. In a pollution control context, 2,4-dinitrophenol (2,4-DNP) degradation was used as probe reaction, with >99 % of this pollutant being removed in presence of H2O2 under visible light. NO 2 − , NO 3 − , hydroxylated compounds, and a carboxylic acid were identified as photoproducts, suggesting a degradation pathway. Finally, catalyst reactivity in biological matrices was evaluated by oxidative degradation of lipids, revealing that α-Fe2O3 is a good oxidative stress inducer, representing a new application for materials based on iron oxides.