Abiotically or microbially mediated transformations of magnetite by sulphide species: The unforeseen role of nitrate-reducing bacteria

摘要

In the anoxic conditions of nuclear waste deep geological repository, the main iron corrosion products formed at the surface of the carbon steel overpacks are siderite ((FeCO3)-C-II) and magnetite ((FeFe2O4)-Fe-II-O-III) that form a rather protective layer. The originality of this work is the consideration of the bacterial metabolism of nitrate-reducing bacteria (NRB), often overlooked in corrosion processes. Klebsiella mobilis was used as a model of NRB and incubated with ferrous carbonates/magnetite corrosion bilayers under anoxic conditions. As a consequence of a combination of biotic and abiotic processes magnetite was reduced to mackinawite ((FeS)-S-II) and subsequently transformed to greigite ((FeFe2S4)-Fe-II-S-II).