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Transformation of natural As-associated ferrihydrite downstream of a remediated mining site

Jerome Gautier, Cecile Grosbois, Alexandra Courtin-Nomade, Jean Pierre Floc'h and Francois Martin
Transformation of natural As-associated ferrihydrite downstream of a remediated mining site
European Journal of Mineralogy (April 2006) 18 (2): 187-195


Natural ferrihydrite, a poorly crystalline iron oxyhydroxide with a high As content, has been studied with respect to its crystallinity in a remediated mining environment in the Saint-Yrieix Au mining district in France. The crystallinity increases from proto-ferrihydrite to a better crystallized 2-line ferrihydrite, while the associated As contents decrease from 7.8 to 1.9 wt.%; this correlation of increasing crystallinity with decreasing As suggests that As is more likely to be coprecipitated in the ferrihydrite structure than adsorbed onto the surface. The evolution of ferrihydrite crystallinity is related to 1) aqueous transformation for samples continuously submerged and controlled by water composition (pH, ionic strength and redox potential) and 2) dry thermal transformations for samples in a seasonally humid area with variations in temperature, humidity, agglomeration and compaction. The evolution of ferrihydrite crystallinity is more pronounced during dry thermal transformation than during aqueous transformations. Although the evolution of ferrihydrite is observed, no stable form (goethite, hematite) is detected as usually noted during dry transformation. This may be explained by incorporated cations such as Si and Al that can inhibit transformation of ferrihydrite to a more stable form. To understand this transformation in a natural environment, the discussion focuses on two main points: 1) the relationship between spatial mineralogical distribution and As content and 2) the importance of ferrihydrite evolution as a function of transformation processes observed in the field.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 18
Serial Issue: 2
Title: Transformation of natural As-associated ferrihydrite downstream of a remediated mining site
Affiliation: Universite de Limoges, Laboratoire HydrASA, Limoges, France
Pages: 187-195
Published: 200604
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 38
Accession Number: 2006-047597
Categories: Mineralogy of non-silicatesEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200626
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