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Structural incorporation of As5+ into hematite
Ralph M Bolanz1, Mária Wierzbicka-Wieczorek, Mária Čaplovičová
1Institute of Geosciences, Friedrich-Schiller-University Jena, 07745 Jena, Germany. Ralph.Bolanz@uni-jena.de
Environmental Science & Technology
|August 6, 2013
Summary
Arsenic immobilization in hematite occurs through crystal incorporation, not just surface adsorption. This new mechanism reveals a potentially long-lasting storage method for arsenic within iron oxides.
Area of Science:
- Geochemistry
- Materials Science
- Environmental Science
Background:
- Hematite (α-Fe2O3), a common iron oxide, acts as a sink for toxic arsenic.
- Arsenic immobilization is primarily attributed to adsorption onto hematite surfaces.
- Incorporation of arsenic within hematite crystals has not been extensively studied.
Purpose of the Study:
- To investigate the potential for arsenic incorporation into hematite crystals.
- To demonstrate a novel mechanism for arsenic immobilization by iron oxides.
- To characterize the structural state and arrangement of incorporated arsenic.
Main Methods:
- Coupling of nanoresolution techniques with X-ray absorption spectroscopy.
- Analysis of arsenic presence and concentration within hematite crystals.
- Structural analysis of arsenic speciation and its relationship with the hematite matrix.
Main Results:
- Evidence of arsenic (up to 1.9 wt%) incorporated within hematite crystals was found.
- Incorporated As(5+) exhibited short-range order resembling angelellite-like clusters.
- These clusters showed epitaxial intergrowth with hematite along specific crystallographic planes.
Conclusions:
- Arsenic incorporation into hematite crystals is a significant immobilization mechanism.
- A structural composite of hematite and angelellite-like clusters offers a new pathway for arsenic storage.
- This mechanism provides a potentially long-lasting sequestration of As(5+) by iron oxides.
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