Immobilization of aqueous Hg(II) by mackinawite (FeS)

Liu, Jianrong; Valsaraj, Kalliat T.; Dévai, István; DeLaune, Ronald D.

doi:10.1016/j.jhazmat.2008.01.006

Cited by 114 publications

(79 citation statements)

References 52 publications

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“…The ranges of %MeHg/Hg in sediments (x = 0.21% for Eastern lagoon; x = 0.12% for Western lagoon) were relatively low when compared to those reported for ''active'' marine sediments (x = 0.47%; (Fitzgerald et al 2007). This suggests two possibilities: (1) activity of the microbial community associated with the sediment and capable of methylation was low, which is probably not the case considering that mercury methylation is a widespread phenomenon even more intense in the tropics; and/or (2) solubility and bioavailability of inorganic Hg was decreased probably through association with sedimentary organic carbon and/or acid-volatile sulfides, and in particular FeS, the mercury then occurring in a particulate form, which is not bioavailable to Hg-methylating organisms and inhibits MeHg production (Hammerschmidt and Fitzgerald 2004;Liu et al 2008). In agreement with the last hypothesis, the fraction of Hg as MeHg was lower in the Western lagoon sediments when compared to those of the Eastern lagoon that contains less organic material.…”

Section: Methylation Of Inorganic Hg Is Variable In the Lagoons Of Lomémentioning

confidence: 99%

Increased Bioavailability of Mercury in the Lagoons of Lomé, Togo: The Possible Role of Dredging

Gnandi

Han

Rezaie-Boroon

et al. 2010

AMBIO

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Surface sediments of the lagoons of Lomé, Togo, were analyzed for mercury, methylmercury, and trace elements. Concentrations were greater than typical for natural lagoon sediments, and with greater variability within the Eastern lagoon compared to the Western one. The Eastern lagoon is larger and has been dredged in the past, while the Western lagoon, which also receives major waste inputs, has not been dredged and shows less tidal flushing. Accordingly, one naturally believes that the Eastern lagoon is cleaner and probably safe to use due to its natural resources, including fishes to eat. Unexpectedly, we describe here that mercury methylation was greater in the Eastern lagoon, indicating increased bioavailability of mercury, as probably facilitated by past dredging that decreased solidphase retention of inorganic mercury. Urbanization has historically been more developed in the southern part of the lagoons, which is still reflected in contamination levels of sediment despite dredging, probably because sources of contamination are still more important there today. Such urban contamination emphasizes the need to regulate waste discharges and possible airborne contamination in growing cities of developing countries, and implements environmental and public health monitoring, especially in relation to misbelieves systematically associated with the cleansing effect of dredging activity.

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Section: Methylation Of Inorganic Hg Is Variable In the Lagoons Of Lomémentioning

confidence: 99%

Increased Bioavailability of Mercury in the Lagoons of Lomé, Togo: The Possible Role of Dredging

Gnandi

Han

Rezaie-Boroon

et al. 2010

AMBIO

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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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“…FeSO 4 . 6 H 2 O (Mohr's salt; Sigma-Aldrich), and Na 2 S 9 H 2 O (Acros Chemicals), using the method described by Liu et al (2008). The experiments were conducted under N 2 , using a glove box, at room temperature (25 o C), and all solutions were previously deoxygenated by purging with N 2 (ultra-pure) for 30 minutes.…”

Section: Synthesis Of Modified Mackinawitementioning

confidence: 99%

“…The unmodified mackinawite (FeS) has low resistance to oxidation (Liu et al, 2008, Wolters et al, 2005. In preliminary analysis (not shown), we observed that FeS oxidized in less than 24 hours.…”

Section: Mackinawite Oxidation -Long Time-scale Experimentsmentioning

confidence: 99%

“…Mackinawite was reported as an effective isolating material for use as a sediment cap (Liu et al, 2009). Although pure mackinawite can immobilize mercury, it has a low stability when exposed to oxidized conditions (Burton et al, 2009;Liu et al, 2008;Wolthers et al, 2005). Under field conditions, the capping material has to be in contact with the oxigenated water column during the capping building.…”

Section: Introductionmentioning

confidence: 99%

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