Refinement of the crystal structure of scorodite

Kitahama, Katsuki; Kiriyama, Ryôiti; Baba, Yoshio

doi:10.1107/s056774087500266x

Cited by 127 publications

(108 citation statements)

References 2 publications

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“…In the spectrum of scorodite, the most likely candidate for the As carrier in the soil, two distinct peaks represent the contributions of the first two shells of neighbours around the As atom. 16 In the spectrum of the soil sample, only the first peak of the nearest coordination shell is similar to that in the mineral, while the characteristic strong peak of the second shell is absent, clearly showing that As in the soil is predominantly not in the form of crystalline scorodite.…”

Section: Resultsmentioning

confidence: 95%

“…For the reference scorodite spectrum an FEFF model was constructed from the crystallographic data. 16 In scorodite, As(V) is coordinated to four oxygen atoms at a distance of 1.68Å in the first coordination shell, and the second coordination shell is composed of four Fe atoms located at distances from 3.35 to 3.38Å and two oxygen atoms, one at 3.24Å and the other, belonging to an OH group, at 3.35Å. The FEFF model, comprising all single scattering paths and all significant multiple scattering paths up to 3.4Å, yields a very good fit in the k range 5-14Å 1 for the R region from 1.1 to 3.3Å (Figs 2 and 3).…”

Section: Resultsmentioning

confidence: 99%

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EXAFS and XANES study of arsenic in contaminated soil

et al. 2005

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Historical mining, processing and refinement of arsenic in purpose built calciners in Cornwall, UK, have resulted in extremely high contamination of soils with arsenic in some localized areas. The x-ray absorption spectroscopic methods XANES (x-ray absorption near-edge structure) and EXAFS (extended x-ray absorption fine structure) were used to retrieve arsenic molecular information, i.e. oxidation state and local structure around As atoms, in the soil from a calciner's residue dump near Camborne (which contained 8.82 wt% arsenic) and identify the most abundant modes of As bonding. The results show that arsenic is predominantly in pentavalent form, tetrahedrally bound to oxygen atoms in the first coordination sphere. Fe and Al atoms are found in the next neighbour coordination shells around As. The As-Fe and As-Al distances and coordination numbers strongly suggest that arsenate in the soil is present in two forms, viz. as amorphous or poorly crystalline hydrous oxides of Fe (most likely FeAsO 4 ) and adsorbed on aluminium (hydr)oxides or aluminosilicates such as clay.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

EXAFS and XANES study of arsenic in contaminated soil

et al. 2005

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“…Theoretical back scattering paths for the fits were calculated from the various crystal structures using FEFF6. Scorodite (Kitahama et al, 1975), tooeleite (Morin et al, 2007) and 4-Hydroxy-3-nitrobenzenearsonic acid (Nuttall and Hunter, 1995) structures were used to extract paths from the backscatters of the As(V), As(III) and organic As species, respectively. Goethite (Hazemann et al, 1991) and Fe-carboxylate (Horcajada et al, 2007) structures were used to obtain the backscattering paths for…”

Section: Xas Data Analysismentioning

confidence: 99%

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Guénet

Davranche

Vantelon

et al. 2017

Geochimica et Cosmochimica Acta

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Highlighting the wide variability in arsenic speciation in wetlands: a new insight into the control of the behavior of arsenic. Geochimica et Cosmochimica Acta, Elsevier, 2017, 203, pp.284-302 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1Highlighting the wide variability in arsenic speciation in wetlands: AbstractAlthough the behavior of Arsenic (As) under reducing conditions in periods of high water levels in wetlands is well understood and documented, there is a lack of information under oxidizing conditions when the water level decreases. In this study, we were interested in the first stage of the oxidizing period, when oxidation products are still in suspension. A soil sample from the Naizin Kervidy wetland (France) was incubated in the laboratory to produce a reduced soil solution. The reduced solution was subsequently oxidized, filtered and ultrafiltered using decreasing pore size membranes (5 µm, 3 µm, 0.2 µm, 30 kDa and 5 kDa). The distribution of As and Fe was investigated in each size fraction of the oxidized solution and their speciations were studied using XAS, HPLC and SEC-ICP-MS. Organic matter was characterized using thermally assisted hydrolysis and methylation gas chromatography-mass spectrometry (THM-GC-MS) and fluorescence spectroscopy. The majority of the As was present as As(V) but a small amount of As(III) still remained despite the advanced oxidized conditions. In the > 0.2 µm fractions, the XAS analyses showed that As was associated, in the second shell, with Fe (As-Fe = 3.35 Å) as bidentate binuclear complexes and C (As-C = 2.90 Å), suggesting the integration of As in biological objects. In the < 30 kDa fraction, As was directly bound to C (As-C = 1.96 Å) in the first shell indicating the presence of organic As species. In the second shell, an As-Fe distance of 3.35 Å was found showing that 2 part of the As was still complexed with Fe. The 0.2 µm-30 kDa fraction was a transitional fraction in terms of the Fe species and OM composition. In this fraction, organic matter exhibited a more humic character (aromatic molecules) inducing an increasing cation binding capacity. As a consequence, in this fraction and in the smallest one, As, Fe and OM seemed to form ternary complexes in which the Fe or nano-oxides in the > 30 kDa fraction and as monomer, or cluster in < 30 kDa fraction acted as a bridge. In all of the fractions, a proportion of As(V) was present as organic methylated species. These organic species might be produced by several organisms (animal or plant) via a detoxification process. They seemed to be bound to the particulate and colloidal Fe/OM phases as well as integ...

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“…In the XRD pattern of the As(V) -goethite sorption sample at the highest concentration, a small peak emerges at ∼28-29 • 2Â (Fig. 5b), which is coincident with the primary diagnostic peak of scorodite (FeAsO 4 ·2H 2 O) and indicates the formation of ferric arsenate phase [40]. The As(V) and Fe 3+ also form amorphous precipitate in solution without obvious XRD peaks (Fig.…”

Section: Sorption and Desorptionmentioning

confidence: 99%