Fate of incorporated metals during mackinawite oxidation in sea water

Holmes, Jennifer L.

doi:10.1016/s0883-2927(98)00056-0

Cited by 30 publications

(17 citation statements)

References 20 publications

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“…Under certain conditions pyrrhotite (Fe 1 − x S) can also form in anoxic sediments (Horng and Roberts, 2006;Larrasoana et al, 2007) (Table 1). In addition to their geological significance, iron sulfide minerals can be used in soil or water remediation: mackinawite was shown to effectively immobilize heavy metals and toxic ions through sorption mechanisms (Watson et al, 1995;Holmes, 1999;Mullet et al, 2004;Livens et al, 2004;Wolthers et al, 2005;Liu et al, 2008;Gallegos et al, 2008;Renock et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Structural properties and transformations of precipitated FeS

et al. 2012

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Editor: J. Fein Keywords:Amorphous iron sulfide Mackinawite Greigite Phase transformations XRD TEM Nanocrystalline iron sulfides form in diverse anoxic environments. The initial precipitate is commonly referred to as nanocrystalline mackinawite (FeS) or amorphous FeS. In order to better understand the structure of the initial precipitate and its conversion to mackinawite and greigite (Fe 3 S 4 ), we studied synthetic iron sulfide samples that were precipitated from hydrous solutions near room temperature. The transformation of precipitated FeS was followed in both aqueous and dry aging experiments using X-ray powder diffraction (XRD) and scanning and transmission electron microscopy (SEM/TEM) and selected-area electron diffraction (SAED). Under tightly controlled anoxic conditions the first precipitate was nanocrystalline mackinawite. In contrast, when anaerobic conditions during synthesis were not completely ensured, freshly precipitated iron sulfide was typically X-ray amorphous (FeS am ), and showed only one broad Bragg-peak at 2Θ = 16.5°(5.4 Å). A distribution of interatomic distances calculated from pair-distribution function analysis of SAED patterns of FeS am showed that only short-range (b 7 Å) order was present in the bulk of the material, with Fe mainly present in tetrahedral coordination. SEM and TEM images confirmed the poorly ordered structure and showed that FeS am formed aggregates of curved, amorphous sheets that contained 3-8 structurally ordered layers at their cores. Such layers are generally assumed to be structurally similar to the tetrahedral iron sulfide layers in mackinawite. However, both inter-and intralayer spacings measured in high-resolution TEM images (~5.3 to 6.3 and~3.0 to 3.1 Å, respectively) were significantly larger than the corresponding spacings in crystalline mackinawite (5.03 and 2.6 Å, respectively), suggesting that short-range structural order within the semi-ordered layers of FeS am was not mackinawite-like. In aqueous aging experiments at room temperature, FeS am transformed into a mixture of mackinawite and greigite in~2 months, and completely converted to platy greigite crystals after~10 months. These aqueous transformations were likely driven by excess sulfur in the reacting solutions. We also studied the conversions of nanocrystalline mackinawite. In order to accelerate phase transitions, the initial FeS precipitate was heated to 120°C, resulting in the formation of crystalline mackinawite within 2 h; at 150°C, the material converted directly to pyrrhotite. Finally, when stored in a dry state at room temperature, crystalline mackinawite converted to greigite in 3 months, much faster than in the equivalent experiments in the aqueous solution, probably as a result of a more oxidative environment. The distinction between FeS am and nanocrystalline mackinawite is significant, since conditions for the formation of both phases are present in natural settings. Our experiments in a well-sealed anaerobic chamber simulate iron sulfide formation under anoxic conditions, where...

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Section: Introductionmentioning

confidence: 99%

Structural properties and transformations of precipitated FeS

et al. 2012

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“…In such situations, Fe sulfides are found to be oxidatively dissolved, causing the release of the associated metals and arsenic to waters (Holmes, 1999;Saulnier and Mucci, 2000;Caetano et al, 2003). Under persistent oxidizing conditions, the released Fe forms insoluble Fe (oxyhydr)oxides, which may subsequently adsorb and/or coprecipitate with the mobilized trace metals and arsenic (Holmes, 1999;Saulnier and Mucci, 2000;Caetano et al, 2003). Fe (oxyhydr)oxides, produced as a result of oxidation, are known to be strong adsorbents for arsenic (Waychunas et al, 1993;Manning and Goldberg, 1996;Fendorf et al, 1997;Farquhar et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Aerobic oxidation of mackinawite (FeS) and its environmental implication for arsenic mobilization

Jeong

Han

Park

et al. 2010

Geochimica et Cosmochimica Acta

176

111

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“…Since many metals can be incorporated into iron sul des, it is of environmental importance to trace the fate of these metals during their oxidation (Bertolin et al 1995). Since iron monosul des oxidize more readily than pyrite, they are prone to release incorporated metals (Holmes 1999). In general, there is no uniform behavior of pollutant metals.…”

Section: Microbial Degradation Of Sul Des In Marine Environmentsmentioning

confidence: 99%