X-ray absorption spectroscopy studies of reactions of technetium, uranium and neptunium with mackinawite

Livens, Francis R.; Jones, Mark; Hynes, Amanda J.; Charnock, John; Mosselmans, J. Frederick W.; Hennig, Christoph; Steele, Helen; Collison, David; Vaughan, David J.; Pattrick, R. A. D.; Reed, Wendy A.; Moyes, Lesley N.

doi:10.1016/j.jenvrad.2004.01.012

Cited by 108 publications

(97 citation statements)

References 17 publications

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“…Mackinawite is the first crystalline iron sulfide phase that is formed in aqueous systems (Wolthers et al 2005) and is a precursor in sedimentary pyrite (FeS 2 ) formation (Wang & Morse 1996). Recent studies have demonstrated that mackinawite is an important natural reductant in soils and sediments for organic and inorganic contaminants (Moyes et al 2000;Moyes et al 2002;Lee & Batchelor 2003;Arias and Tabo 2003;Livens et al 2004;Bruggeman et al 2005).…”

Section: Transport and Redox Reactionsmentioning

confidence: 99%

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides. 3. Influence of Chemical Speciation and Bioavailability on Contaminants Immobilization/Mobilization Bio-processes

Hullebusch

Lens

Tabak

2005

Rev Environ Sci Biotechnol

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The biotransformation of metals is an exciting, developing strategy to treat metal contamination, especially in environments that are not accessible to other remediation technologies. However, our ability to benefit from these strategies hinges on our ability to monitor these transformations in the environment. That's why remediation of contaminated sediments and soil requires detailed in situ characterization of the speciation of the toxic substances and their transformations with respect to time and spatial distribution. The present paper gives an overview of the literature regarding research performed in the laboratory as well as in the field.

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Section: Transport and Redox Reactionsmentioning

confidence: 99%

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides. 3. Influence of Chemical Speciation and Bioavailability on Contaminants Immobilization/Mobilization Bio-processes

Hullebusch

Lens

Tabak

2005

Rev Environ Sci Biotechnol

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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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“…The interaction between iron sulfide and TcO 4 − showed that TcO 4 − in aqueous solution could be effectively reduced and coprecipitated with FeS [31][32][33][34], with a TcS 2 -like product identified by X-ray absorption spectroscopy [35][36][37]. Further studies on the reoxidation of the FeS host with aging showed that rather than being oxidized back to TcO 4 − , a TcO 2 -like phase formed, indicating that long term immobilization might be achieved [36,37]. Based on these results, it may be possible to inject H 2 S gas into the vadose zone to reduce the iron oxides to FeS, creating a permeable reactive barrier of FeS for preventing the migration of TcO 4 − .…”

Section: Introductionmentioning

confidence: 99%