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Formation of green rust sulfate : a combined in situ time-resolved X-ray scattering and electrochemical study.

Ahmed, Imad A. M. and Benning, Liane G. and Kakonyi, Gabriella and Sumoondur, Aryani D. and Terrill, Nick J. and Shaw, Samuel (2010) Formation of green rust sulfate : a combined in situ time-resolved X-ray scattering and electrochemical study. Langmuir, 26 (9). pp. 6593-6603. ISSN 1520-5827

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Abstract

The mechanism of green rust sulfate (GR-SO4) formation was determined using a novel in situ approach combining time-resolved synchrotron-based wide-angle X-ray scattering (WAXS) with highly controlled chemical synthesis and electrochemical (i.e., Eh and pH) monitoring of the reaction. Using this approach,GR-SO4 was synthesized under strictly anaerobic conditions by coprecipitation from solutions with known FeII/FeIII ratios (i.e., 1.28 and 2) via the controlled increase of pH. The reaction in both systems proceeded via a three-stage precipitation and transformation reaction. During the first stage,schwertmannite (Fe8O8(OH)4.5(SO4)1.75) precipitated directly from solution at pH 2.8−4.5. With increasing pH (>5), Fe2+ ions adsorb to the surface of schwertmannite and catalyze its transformation to goethite (α-FeOOH) during the second stage of the reaction. In the third stage, the hydrolysis of the adsorbed Fe2+ ions on goethite initiates its transformation to GR-SO4 at pH >7. The GR-SO4 then continues to crystallize up to pH ∼8.5. These results suggest that with an FeII/FeIII ratio of ≤2 in the initial solution the structural FeII/FeIII of the GR-SO4 will be close to that of the starting composition.

Item Type: Article
Journal or Publication Title: Langmuir
Uncontrolled Keywords: Green Rust ; Stability ; Synchrotron ; X-ray Scattering ; SAXS ; WAXS ; Schwertmannite ; Goethite ; X-ray Diffraction
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 33827
Deposited By: Dr Imad Ahmed
Deposited On: 19 Jul 2010 10:12
Refereed?: Yes
Published?: Published
Last Modified: 21 Sep 2017 03:49
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/33827

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