A poorly crystallized oxyhydroxysulfate of iron formed by bacterial oxidation of Fe(II) in acid mine waters

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90009-A· OSTI ID:6032794

Bigham, J M ^[1]; Schwertmann, U; Murad, E ^[2]; Carlson, L ^[3]

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1. Ohio State Univ., Columbus (USA)
2. Technische Universitaet Muenchen (West Germany)
3. Univ. of Helsinki (Finland)

A poorly crystallized oxyhydroxysulfate of Fe has been identified as the primary component of ochreous precipitates from sulfate-rich mine waters having pH values in the range of 2.5 to 4.0. The compound is characterized by rapid dissolution in acid (pH 3.0) ammonium oxalate, an Fe/S mole ratio ranging from 5 to 8, a high specific surface area (175-225 m{sup 2}/g), a yellowish brown (9.0-10.0 YR) color, a fibrous morphology, and a broad, 8-line x-ray diffraction profile. Analyses of synthetic analogs prepared by hydrolysis of 0.02 M FeCl{sub 3} solutions containing up to 2,000 {mu}g/mL SO{sub 4} show the material to have a tunnel structure akin to that of akaganeite ({beta}-FeOOH). Sulfate occurs both as a bridging element between Fe atoms lining adjacent walls of the tunnels and as a specifically adsorbed surface component. Extraction of the tunnel SO{sub 4} destabilizes the structure and causes the compound to transform to goethite ({alpha}-FeOOH) under ambient conditions. Moessbauer spectra taken at 4.2 K yield hyperfine fields lower than those of even the most poorly crystallized iron oxides, indicating that SO{sub 4} inhibits magnetic ordering. A tetragonal unit cell with a{sub 0} = 1.065 and c{sub 0} = 0.604 nm is proposed to describe the structure. The corresponding unit cell formula is Fe{sub 16}O{sub 16}(OH){sub 12}(SO{sub 4}){sub 2} but may range to Fe{sub 16}O{sub 16}(OH){sub 10}(SO{sub 4}){sub 3} depending upon the degree of saturation of the tunnel and surface sites with SO{sub 4}. Because of its abundance and high surface reactivity, this compound should play an important role in regulating the solubilities of both major and trace elements in surface waters impacted by acid mine drainage.

• OSTI ID: 6032794
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 54:10; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
ACID MINE DRAINAGE
GEOCHEMISTRY
IRON SULFATES
PRECIPITATION
STRUCTURAL CHEMICAL ANALYSIS
CRYSTAL STRUCTURE
CRYSTALLIZATION
DISSOLUTION
PH VALUE
SOLUBILITY
SULFATE MINERALS
WATER CHEMISTRY
CHEMISTRY
IRON COMPOUNDS
MINERALS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SEPARATION PROCESSES
SULFATES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
010900* - Coal
Lignite
& Peat- Environmental Aspects
540320 - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)
580000 - Geosciences