Formation of Green Rust Sulfate: A Combined in Situ Time-Resolved X-ray Scattering and Electrochemical Study

被引：61
作者：
Ahmed, Imad A. M. [1 ]
Benning, Liane G. [1 ]
Kakonyi, Gabriella [1 ]
Sumoondur, Aryani D. [1 ]
Terrill, Nick J. [2 ]
Shaw, Samuel [1 ]
机构：
[1] Univ Leeds, Sch Earth & Environm, Leeds LS2 9JT, W Yorkshire, England
[2] Diamond Light Source, Oxford, England
来源：
LANGMUIR | 2010年 / 26卷 / 09期
基金：
英国自然环境研究理事会;
关键词：
ACID-MINE DRAINAGE; SCHWERTMANNITE TRANSFORMATION; IRON; FE(II); CARBONATE; HYDROXIDE; GOETHITE; FERRIHYDRITE; MOSSBAUER; COPRECIPITATION;
D O I：
10.1021/la903935j
中图分类号：
O6 [化学];
学科分类号：
0703 ;
摘要：
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 Fe-II/Fe-III ratios (i.e., 1.28 and 2) via the controlled increase or pH. The reaction in both systems proceeded via a three-stage precipitation and transformation reaction. During the first stage,schwertmannite (Fe8O5(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 (alpha-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 similar to 8.5. These results suggest that with an Fe-II/Fe-III ratio of <= 2 in the initial solution the structural Fe-II/Fe-III of the GR-SO4 will be close to that of the starting composition.
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收藏
页码：6593 / 6603
页数：11
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