Nitrite reduction by biogenic hydroxycarbonate green rusts: Evidence for hydroxyl-nitrite green rust formation as an intermediate reaction product

Abstract : The present study investigates for the first time the reduction of nitrite by biogenic hydroxycarbonate green rusts, bio-GR(CO3), produced from the bioreduction of ferric oxyhydroxycarbonate (Fohc), a poorly crystalline solid phase, and of lepidocrocite, a well-crystallized Fe(III)-oxyhydroxide mineral. Results show a fast Fe(II) production from Fohc, which leads to the precipitation of bio-GR(CO3) particles that were roughly 2-fold smaller (2.3 ± 0.4 μm) than those obtained from the bioreduction of lepidocrocite (5.0 ± 0.4 μm). The study reveals that both bio-GR(CO3) are capable of reducing nitrite ions into gaseous nitrogen species such as NO, N2O, or N2 without ammonium production at neutral initial pH and that nitrite reduction proceeded to a larger extent with smaller particles than with larger ones. On the basis of the identification of intermediates and endreaction products using X-ray diffraction and X-ray absorption fine structure (XAFS) spectroscopy at the Fe K-edge, our study shows the formation of hydroxy-nitrite green rust, GR(NO2), a new type of green rust 1, and suggests that the reduction of nitrite by biogenic GR(CO3) involves both external and internal reaction sites and that such a mechanism could explain the higher reactivity of green rust with respect to nitrite, compared to other mineral substrates possessing only external reactive sites.
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Submitted on : Wednesday, February 18, 2015 - 5:36:47 PM
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Delphine Guerbois, Georges Ona-Nguema, Guillaume Morin, Mustapha Abdelmoula, Anniet M. Laverman, et al.. Nitrite reduction by biogenic hydroxycarbonate green rusts: Evidence for hydroxyl-nitrite green rust formation as an intermediate reaction product. Environmental Science and Technology, American Chemical Society, 2014, 48 (8), pp.4505-4514. ⟨10.1021/es404009k ⟩. ⟨hal-01118327⟩

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