Redetermination of iron(III) arsenate dihydrate

Xu, Yan; Zhou, Guangpeng; Zheng, Xiaohui

doi:10.1107/s1600536807005302

Cited by 25 publications

(8 citation statements)

References 12 publications

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“…Solid lines are data; dashed lines are fits (fit results in Table 3). [38]. d A-B is the absorber-backscatterer pair; N is the number of backscattering atoms at distance (R); σ 2 (Debye Waller term) is the absorber-backscatterer mean-square relative displacement; ∆E O is the energy shift in the least-squares fit; χ 2 is a reduced least-squares goodness-of-fit parameter (=(F-factor)/(#points -#variables)); scale factor (S 2 o ) fixed at 1. e Fraction corresponded to (a.)…”

Section: Discussionmentioning

confidence: 99%

Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek

Serrano

Gomez-Gonzalez

O’Day

et al. 2015

Journal of Hazardous Materials

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Arsenic and iron speciation in the dispersible colloid fraction (DCF; 10-1000 nm) from an As-rich mine waste pile, sediments of a streambed that collects runoff from waste pile, the streambed subsoil, and the sediments of a downstream pond were investigated by combining asymmetrical-flow field-flow fractionation (AsFlFFF)/inductively-coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and X-ray absorption (XAS) spectroscopy. Calcium, Fe and As (Fe/As molar ratio ∼ 1) were the main components of the DCF from waste pile. TEM/EDS and As and Fe XAS analysis revealed the presence of nanoparticle scorodite in this same DCF, as well as Fe nanoparticles in all samples downstream of the waste pile. Arsenic and Fe XAS showed As(V) adsorbed onto nanoparticulate ferrihydrite in the DCF of downstream samples. Micro-X-ray fluorescence indicated a strong correlation between Fe and As in phyllosilicate/Fe(3+) (oxi) hydroxide aggregates from the sediment pond. Fractionation analysis showed the mean particle size of the DCF from the streambed sample to be smaller than that of the streambed subsoil and sediment ponds samples. These results show that an important and variable fraction of As may be bound to dispersible colloids that can be released from contaminated soils and transported downstream in natural systems.

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Section: Discussionmentioning

confidence: 99%

Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek

Serrano

Gomez-Gonzalez

O’Day

et al. 2015

Journal of Hazardous Materials

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“…The details about XAS data collection and analysis are in the SI. The XAS data analysis was completed using earlier published approaches. − The Fe and Se K-edge XANES spectra were analyzed by linear combination fitting using Fe(III), Fe(II), and Se(IV) and Se(VI) standards.…”

Section: Methodsmentioning

confidence: 99%

Redox Transformations of As and Se at the Surfaces of Natural and Synthetic Ferric Nontronites: Role of Structural and Adsorbed Fe(II)

Ilgen

Kruichak

Artyushkova

et al. 2017

Environ. Sci. Technol.

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Adsorption and redox transformations on clay mineral surfaces are prevalent in surface environments. We examined the redox reactivity of iron Fe(II)/Fe(III) associated with natural and synthetic ferric nontronites. Specifically, we assessed how Fe(II) residing in the octahedral sheets, or Fe(II) adsorbed at the edge sites alters redox activity of nontronites. To probe the redox activity we used arsenic (As) and selenium (Se). Activation of both synthetic and natural ferric nontronites was observed following the introduction of Fe(II) into predominantly-Fe(III) octahedral sheets or through the adsorption of Fe(II) onto the mineral surface. The oxidation of As(III) to As(V) was observed via catalytic (oxic conditions) and, to a lesser degree, via direct (anoxic conditions) pathways. We provide experimental evidence for electron transfer from As(III) to Fe(III) at the natural and synthetic nontronite surfaces, and illustrate that only a fraction of structural Fe(III) is accessible for redox transformations. We show that As adsorbed onto natural and synthetic nontronites forms identical adsorption complexes, namely inner-sphere binuclear bidentate. We show that the formation of an inner-sphere adsorption complex may be a necessary step for the redox transformation via catalytic or direct oxidation pathways.

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“…XAFS data were processed using the Athena and SixPack interfaces to IFEFFIT . Backscattering phase and amplitude functions for structural analysis of the extended X-ray absorption fine structure (EXAFS) spectra were calculated using FEFF 7.02 from the structure of scorodite, FeAsO 4 ·2H 2 O . The amplitude reduction factor, S 0 2 , was fixed to 1.0 for fitting.…”

Section: Methodsmentioning

confidence: 99%

“…48 Backscattering phase and amplitude functions for structural analysis of the extended X-ray absorption fine structure (EXAFS) spectra were calculated using FEFF 7.02 49 from the structure of scorodite, FeAsO 4 3 2H 2 O. 50 The amplitude reduction factor, S 0 2 , was fixed to 1.0 for fitting. All spectra for each mineral were refined versus a single starting structural model consisting of AsÀO and AsÀFe single scattering paths and three multiple scattering paths: a triangular AsÀOÀO path, a collinear AsÀOÀAsÀO path, and a noncollinear AsÀOÀAsÀO path.…”

Section: ' Introductionmentioning

confidence: 99%

Effect of Aqueous Fe(II) on Arsenate Sorption on Goethite and Hematite

Catalano¹,

Luo²,

Otemuyiwa³

2011

Environ. Sci. Technol.

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Biogeochemical iron cycling often generates systems where aqueous Fe(II) and solid Fe(III) oxides coexist. Reactions between these species result in iron oxide surface and phase transformations, iron isotope fractionation, and redox transformations of many contaminant species. Fe(II)-induced recrystallization of goethite and hematite has recently been shown to cause the repartitioning of Ni(II) at the mineral-water interface, with adsorbed Ni incorporating into the iron oxide structure and preincorporated Ni released back into aqueous solution. However, the effect of Fe(II) on the fate and speciation of redox inactive species incompatible with iron oxide structures is unclear. Arsenate sorption to hematite and goethite in the presence of aqueous Fe(II) was studied to determine whether Fe(II) causes substantial changes in the sorption mechanisms of such incompatible species. Sorption isotherms reveal that Fe(II) minimally alters macroscopic arsenate sorption behavior except at circumneutral pH in the presence of elevated concentrations (10⁻³ M) of Fe(II) and at high arsenate loadings, where a clear signature of precipitation is observed. Powder X-ray diffraction demonstrates that the ferrous arsenate mineral symplesite precipitates under such conditions. Extended X-ray absorption fine structure spectroscopy shows that outside this precipitation regime arsenate surface complexation mechanisms are unaffected by Fe(II). In addition, arsenate was found to suppress Fe(II) sorption through competitive adsorption processes before the onset of symplesite precipitation. This study demonstrates that the sorption of species incompatible with iron oxide structure is not substantially affected by Fe(II) but that such species may potentially interfere with Fe(II)-iron oxide reactions via competitive adsorption.

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Redetermination of iron(III) arsenate dihydrate

Abstract: Key indicatorsSingle-crystal X-ray study T = 293 K Mean (e-O) = 0.003 Å R factor = 0.024 wR factor = 0.059 Data-to-parameter ratio = 10.6For details of how these key indicators were automatically derived from the article, see

Cited by 25 publications

References 12 publications

Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek

Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek

Redox Transformations of As and Se at the Surfaces of Natural and Synthetic Ferric Nontronites: Role of Structural and Adsorbed Fe(II)

Effect of Aqueous Fe(II) on Arsenate Sorption on Goethite and Hematite

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