Journal
APPLIED CLAY SCIENCE
Volume 64, Issue -, Pages 38-43Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.clay.2011.10.008
Keywords
Iron; Green rust; Mossbauer; Fougerite; Layered double hydroxides
Funding
- Agence Nationale de la Recherche (ANR)
- Agence de la Maitrise de l'Energie (ADEME) [0994 C0103]
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This laboratory study describes the abiotic mineralogical transformation of ferrihydrite (F), goethite (G) and hematite (H) into mixed Fe-II-Fe-III green rust (GR). Stoichiometric quantities of ferric oxides were reacted with hydroxylated Fe-II species under static batch conditions at a final pH of similar to 6.3 for 2 h. Mossbauer spectroscopy and transmission electron microscopy (TEM) was used to characterize initial and resulting transformation products. Results indicate that the order of reactivity to transform into GR is F>G>H. Complete transformation of F into GR was achieved while about half of G or H was transformed although G or H are known for their higher thermodynamic stability. As expected, the concentration of soluble iron at the end of the experiment followed the order H>G>F which is in agreement with the predictions of the Fe-II-Fe-III mass balance diagram. The formation kinetics of GR is much higher than that observed for magnetite (Fe3O4) under similar experimental conditions. Therefore in the environment, when hydroxylated Fe-II species interact with ferric oxides, fougerite, the mineral counter part of GR, could be preferentially formed. (C) 2011 Elsevier B.V. All rights reserved.
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