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Article Dans Une Revue Journal of Physical Chemistry C Année : 2023

Phosphate Boosts Nonhydroxyl Radical Species Production upon Air Oxidation of Magnetite and Iron Sulfides at Neutral pH

Résumé

Heterogeneous Fenton-like reactions using O2 as sole oxidant are gaining interest for designing organic contaminant degradation in soils and groundwaters, since they may provide alternatives to current processes involving strong oxidants. Indeed, several Fe(II)-bearing oxide and sulfide mineral phases have been proven to generate reactive species upon air-oxidation. However, the mechanisms of these reactions and the identity of reactive species produced upon oxygenation may deserve further research. Here, we show using Electron Paramagnetic Resonance (EPR) spectroscopy combined with the 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) spin-trap, that air oxidation of pH7 phosphate buffered aqueous suspensions of magnetite (Fe3O4) or mackinawite (FeS) nanoparticles produces a reactive species that is distinct from the hydroxyl radical (•OH) and abstracts a hydrogen atom from ethanol. This reactive species grows dramatically with phosphate concentration, and ultra-filtration reveals that it occurs as both aqueous and surface species. Based on these evidences and from extant reports, we hypothesize that the non-hydroxyl reactive species produced is Fe(IV), whose formation is enhanced in the presence of phosphate ligands. Fe3O4 magnetite (~14 nm) generates about 30% more of this putative ferryl species than FeS mackinawite (~9 nm), while FeS2 (pyrite ~12 nm + marcasite ~4 nm) appears unreactive under these conditions.
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hal-04248112 , version 1 (18-10-2023)

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Guillaume Morin, Frédéric Averseng, Xavier Carrier, Pierre Le Pape, Yishan Du, et al.. Phosphate Boosts Nonhydroxyl Radical Species Production upon Air Oxidation of Magnetite and Iron Sulfides at Neutral pH. Journal of Physical Chemistry C, 2023, 127 (20), pp.9650-9662. ⟨10.1021/acs.jpcc.3c02236⟩. ⟨hal-04248112⟩
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