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Biomineralization and fate of the FeII-FeIII hydroxy salt green rust vs. magnetite

Abstract : It is well known that iron oxide reduction by Shewanella spp. bacteria promotes the formation of FeII bearing minerals, such as the mixed FeII-FeIII hydroxysalt green rusts (GRs), in anaerobic conditions. Although the microbial-promoted generation of GRs is widely demonstrated, the mechanisms and factors governing the GR formation as the main secondary iron mineral at the expense of other products in lab-scale investigations or environmental systems are largely unknown. As GR is an effective reductant for several contaminants the mechanism controlling the formation routes of GR merit investigation, from both the environmental and engineering points of view. Some factors such as cellular material (i.e. autoclaved cells and/or bacterial polymers), synthetic anionic polymers or oxyanions have been identified to control the route of the GR mineralization as secondary mineral at the expense of other products such as magnetite. The arrangement mode of the heterogeneous aggregates resulting from the interactions between bacterial cells , iron oxide particles and polymers was suggested to influence the routes of formation of secondary iron minerals by limiting the diffusion of reactive species and thus creating favorable microenvironment for GR formation. In these aggregates, the electron transfer from cells to iron oxides is supported by organic electron shuttles. On the other hand, anionic polymers, colloidal and aqueous silicates were found to also influence the nature of the secondary iron minerals through the stabilization of the G R crystals. The e results indicate clearly that the bacterial cells d rive indirectly the nature of the secondary FeII-bearing mineral. Moreover, they give new insights into the understanding of the mechanisms of « biogenic » mineral formation based on the electron transfers from bacteria towards iron oxides. Finally, this work contributes to our understanding of the processes leading to green rust formation in environmental systems, such as soils or aquatic systems bio films , in which a very high cell density can be found at a micro-scale level, associated to exo-cellular polymers and natural silica mineral composites .
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  • HAL Id : hal-01508477, version 1



Frédéric Jorand, Asfaw Zegeye, Anne-Sophie Sergent, Paul-Philippe Rémy, Bruno Lartiges, et al.. Biomineralization and fate of the FeII-FeIII hydroxy salt green rust vs. magnetite . 22nd Goldschmidt Conference, Geochemical Society; European Association of Geochemistry; GEOTOP; UQAM, Jun 2012, Montréal, Canada. pp.1907. ⟨hal-01508477⟩



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