Incorporation of Cr, Mn and Ni into goethite (α-FeOOH): mechanism from extended X-ray absorption fine structure spectroscopy

Clay Minerals ◽  
2002 ◽  
Vol 37 (4) ◽  
pp. 639-649 ◽  
Author(s):  
Balwant Singh ◽  
D. M. Sherman ◽  
R. J . Gilkes ◽  
M. A. Wells ◽  
J . F. W. Mosselmans
Keyword(s):  
Transition Metals ◽  
Ore Deposits ◽  
Isomorphous Substitution ◽  
Surface Complexes ◽  
Coordination Environment ◽  
X Ray ◽  
Chemical Mechanisms ◽  
Local Coordination ◽  
X Ray Absorption ◽  
Laterite Ore

AbstractThe crystal-chemical mechanisms by which transition metals are associated with goethite are fundamental to our understanding of the solubility and bioavailability of micronutrients and heavy metals in soils, and in the formation of laterite ore deposits. Transition metals such as Cr, Mn and Ni may sorb onto goethite by forming surface precipitates, surface complexes or by replacing Fe3+ in the goethite structure. In the work reported here, we investigated the local coordination environment of Cr, Mn and Ni in synthetic goethite using EXAFS spectroscopy. We demonstrate the isomorphous substitution for Fe3+ by Cr3+ (up to 8 mol.%), Mn3+ (up to 15 mol.%) and Ni2+ (up to 5 mol.%). We find, however, that the next-nearest-neighbour coordination environment changes with composition. The perturbations are likely to be responsible for limiting the accommodation of Cr3+, Mn3+ or Ni2+ in the FeOOH structure.

Manganese speciation in soils using X-ray absorption spectroscopy

2020 ◽  
Author(s):  
Teresa Zahoransky ◽  
Christian Mikutta
Keyword(s):  
Absorption Spectroscopy ◽  
Chemical Reactivity ◽  
Mixed Valence ◽  
Oxidation States ◽  
Plant Residues ◽  
Edge Structure ◽  
Coordination Environment ◽  
X Ray ◽  
Local Coordination ◽  
X Ray Absorption

<p>Being one of Earth´s most redox-active elements, manganese participates in a great variety of environmental processes and is recognized as a key player controlling carbon turnover and oxidative transformation of organic and inorganic pollutants in soils. Moreover, Mn(III), Mn(IV) or mixed-valence Mn(III/IV) oxides and (oxy)hydroxides are highly effective sorbents for metal pollutants and nutrients in soils. Chemical reactivity, mobility, and bioavailability of Mn depend crucially on its speciation (chemical form). Yet, speciation studies on soil Mn are scarce. Therefore, we employed Mn K-edge (6,539 eV) X-ray absorption spectroscopy (XAS) to determine the oxidation states and local coordination environment (<5 Å) of Mn in oxic bulk soils (Cambisols, Luvisols, Stagnosol) from various field sites in Germany. Our XAS analyses cover 23 soil L, O, A, B, and C horizons exhibiting total Mn concentrations of between 200 and 2,300 mg/kg. For comparison, we also analyze a suite of 31 Mn reference compounds, including Mn carbonate, phosphate, oxides and (oxy)hydroxides, silicates, organic Mn compounds as well as clay and hydroxide minerals with adsorbed Mn(II). X-ray absorption near-edge structure (XANES) spectra are evaluated for the oxidation states of soil Mn using linear combination fit (LCF) analysis. In addition, the average local coordination environment of Mn in the soil samples is assessed by shell-fitting of extended X-ray absorption fine structure (EXAFS) spectra. Based on our XAS results, we will test the following hypotheses: (1) Soil L/O horizons comprise predominantly organically complexed Mn(II) and Mn(III), dominated by the former Mn species; (2) soil A horizons are dominated by Mn(III/IV) in Mn(III/IV)-oxide structures owing to high microbial activity, release of Mn(II) from primary silicates and/or plant residues, and its subsequent (a)biotic oxidation and precipitation as Mn(III/IV) oxides; (3) soil B horizons of different genesis differ in their bulk Mn speciation; Bt horizons of Luvisols are dominated by Mn(II) associated with phyllosilicates, whereas the Stagnosol Bg horizon is dominated by layer-type Mn(III/IV) oxides. In summary, our study will provide first comprehensive data on bulk Mn speciation in three major European soil types. This knowledge is a prerequisite for a better understanding of the biogeochemical Mn cycle in soils.</p>

scholarly journals PyXAS – an open-source package for 2D X-ray near-edge spectroscopy analysis

2020 ◽  
Vol 27 (2) ◽  
pp. 567-575 ◽  
Author(s):  
Mingyuan Ge ◽  
Wah-Keat Lee
Keyword(s):  
Heterogeneous Systems ◽  
Xanes Spectrum ◽  
Oxidation States ◽  
Spectroscopy Analysis ◽  
Coordination Environment ◽  
X Ray ◽  
Local Coordination ◽  
Spatially Resolved ◽  
Manual Analysis ◽  
X Ray Absorption

In the synchrotron X-ray community, X-ray absorption near-edge spectroscopy (XANES) is a widely used technique to probe the local coordination environment and the oxidation states of specific elements within a sample. Although this technique is usually applied to bulk samples, the advent of new synchrotron sources has enabled spatially resolved versions of this technique (2D XANES). This development has been extremely powerful for the study of heterogeneous systems, which is the case for nearly all real applications. However, associated with the development of 2D XANES comes the challenge of analyzing very large volumes of data. As an example, a single 2D XANES measurement at a synchrotron can easily produce ∼106 spatially resolved XANES spectra. Conventional manual analysis of an individual XANES spectrum is no longer feasible. Here, a software package is described that has been developed for high-throughput 2D XANES analysis. A detailed description of the software as well as example applications are provided.

Identification of Transition Metal Sites in Fused SiO2 by X-Ray Absorption Spectroscopy

1985 ◽  
Vol 61 ◽  
Author(s):  
Farrel W. Lytle ◽  
Robert B. Greegor
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Absorption Spectroscopy ◽  
Optical Data ◽  
Site Symmetry ◽  
X Ray ◽  
Hydrolysis Method ◽  
Fused Quartz ◽  
X Ray Absorption ◽  
Good Agreement

ABSTRACTX-ray absorption spectroscopy is used to determine valence and site symmetry for all the 3d transition metals in fused quartz prepared by the flame hydrolysis method. The results are compared with optical data on the same samples with generally good agreement.

In situ x-ray absorption study of lead ion surface complexes at the goethite-water interface

Langmuir ◽  
1991 ◽  
Vol 7 (2) ◽  
pp. 367-373 ◽  
Author(s):  
A. Lawrence. Roe ◽  
Kim F. Hayes ◽  
Catherine. Chisholm-Brause ◽  
Gordon E. Brown ◽  
George A. Parks ◽  
...  
Keyword(s):  
Lead Ion ◽  
Water Interface ◽  
Absorption Study ◽  
Surface Complexes ◽  
X Ray ◽  
X Ray Absorption

X-ray absorption spectroscopy study of the electronic structure and local coordination of 1st row transition metal-promoted Chevrel-phase sulfides

2019 ◽  
Vol 72 (8) ◽  
pp. 1322-1335 ◽  
Author(s):  
Joseph T. Perryman ◽  
Forrest P. Hyler ◽  
Jessica C. Ortiz-Rodríguez ◽  
Apurva Mehta ◽  
Ambarish R. Kulkarni ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Absorption Spectroscopy ◽  
Spectroscopy Study ◽  
X Ray ◽  
Local Coordination ◽  
Chevrel Phase ◽  
X Ray Absorption

Local coordination geometry around Cu and Cu ions in silicate glasses: an X-ray absorption near edge structure investigation

2000 ◽  
Vol 14 (2) ◽  
pp. 211-216 ◽  
Author(s):  
C. Maurizio ◽  
F. d'Acapito ◽  
M. Benfatto ◽  
S. Mobilio ◽  
E. Cattaruzza ◽  
...  
Keyword(s):  
Silicate Glasses ◽  
Coordination Geometry ◽  
Structure Investigation ◽  
Edge Structure ◽  
X Ray ◽  
Local Coordination ◽  
X Ray Absorption ◽  
Cu Ions
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