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dc.contributor.authorMikutta, Christianen_UK
dc.contributor.authorSchröder, Christianen_UK
dc.contributor.authorMichel, F Marcen_UK
dc.description.abstractAmorphous ferric arsenate (AFA, FeAsO4•xH2O) is an important As precipitate in a range of oxic As-rich environments, especially acidic sulfide-bearing mine wastes. Its structure has been proposed to consist of small polymers of single corner-sharing FeO6 octahedra (rFe-Fe ~3.6Å) to which arsenate is attached as a monodentate binuclear 2C complex (‘chain model’). Here, we analyzed the structure of AFAs and analogously prepared amorphous ferric phosphates (AFPs, FePO4•xH2O) by a combination of high-energy total X-ray scattering, Fe K-edge X-ray absorption spectroscopy, and 57Fe Mössbauer spectroscopy. Pair distribution function (PDF) analysis of total X-ray scattering data revealed that the coherently scattering domain size of AFAs and AFPs is about 8Å. The PDFs of AFA lacked Fe-Fe pair correlations at r ~3.6Å indicative of single-corner sharing FeO6 octahedra, which strongly supports a local scorodite (FeAsO4•2H2O) structure. Likewise, PDF analyses as well as wavelet-transform and shell-fit analyses of Fe K-edge extended X-ray absorption fine structure data of the AFPs suggest a local strengite (FePO4•2H2O) structure with isolated FeO6 octahedra being corner-linked to PO4 tetrahedra (rFe-P = 3.25(1)Å). Mössbauer spectroscopy analyses of AFAs and AFPs indicated a strong superparamagnetism. While the AFAs only showed a weak onset of magnetic hyperfine splitting at 5 K, magnetic ordering of the AFPs was completely absent at this temperature. Mössbauer spectroscopy may thus offer a convenient way to identify and quantify AFA and AFP in mineral mixtures containing poorly crystalline Fe(III)-oxyhydroxides. In summary, our results imply a close structural relationship between AFA and AFP and suggest that these amorphous materials serve as templates for the formation of scorodite and strengite (phosphosiderite) in strongly acidic low-temperature environments.en_UK
dc.relationMikutta C, Schröder C & Michel FM (2014) Total X-ray Scattering, EXAFS, and Mössbauer Spectroscopy Analyses of Amorphous Ferric Arsenate and Amorphous Ferric Phosphate. Geochimica et Cosmochimica Acta, 140, pp. 708-719.
dc.rightsBecause the funder, Swiss National Science Foundation has a policy that articles must be archived in an Open Access archive, the publisher, Elsevier, does not allow this work to be made publicly available in this Repository. Please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study.en_UK
dc.subjectamorphous ferric arsenateen_UK
dc.subjectamorphous ferric phosphateen_UK
dc.subjectmine wasteen_UK
dc.subjectMössbauer spectroscopyen_UK
dc.subjecttotal X-ray scatteringen_UK
dc.subjectX-ray absorption spectroscopyen_UK
dc.titleTotal X-ray Scattering, EXAFS, and Mössbauer Spectroscopy Analyses of Amorphous Ferric Arsenate and Amorphous Ferric Phosphateen_UK
dc.typeJournal Articleen_UK
dc.rights.embargoreason[Geochimica et Cosmochimica Acta 2014.pdf] The publisher does not allow this work to be made publicly available in this Repository therefore there is an embargo on the full text of the work.en_UK
dc.citation.jtitleGeochimica et Cosmochimica Actaen_UK
dc.type.statusAM - Accepted Manuscripten_UK
dc.contributor.affiliationETH Zurichen_UK
dc.contributor.affiliationBiological and Environmental Sciencesen_UK
dc.contributor.affiliationVirginia Polytechnic Institute And State Universityen_UK
rioxxterms.apcnot requireden_UK
rioxxterms.typeJournal Article/Reviewen_UK
local.rioxx.authorMikutta, Christian|en_UK
local.rioxx.authorSchröder, Christian|0000-0002-7935-6039en_UK
local.rioxx.authorMichel, F Marc|en_UK
local.rioxx.projectInternal Project|University of Stirling|
local.rioxx.filenameGeochimica et Cosmochimica Acta 2014.pdfen_UK
Appears in Collections:Biological and Environmental Sciences Journal Articles

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