scholarly journals Reduction of Hg(II) by Fe(II)-Bearing Smectite Clay Minerals

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1079
Author(s):  
Edward J. O’Loughlin ◽  
Maxim I. Boyanov ◽  
Kenneth M. Kemner ◽  
Korbinian O. Thalhammer
Keyword(s):  
Clay Minerals ◽  
Smectite Clay ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Synthetic Mica ◽  
Smectite Clays ◽  
Redox Active ◽  
Soils And Sediments ◽  
Clay Suspensions ◽  
X Ray Absorption

Aluminosilicate clay minerals are often a major component of soils and sediments and many of these clays contain structural Fe (e.g., smectites and illites). Structural Fe(III) in smectite clays is redox active and can be reduced to Fe(II) by biotic and abiotic processes. Fe(II)-bearing minerals such as magnetite and green rust can reduce Hg(II) to Hg(0); however, the ability of other environmentally relevant Fe(II) phases, such as structural Fe(II) in smectite clays, to reduce Hg(II) is largely undetermined. We conducted experiments examining the potential for reduction of Hg(II) by smectite clay minerals containing 0–25 wt% Fe. Fe(III) in the clays (SYn-1 synthetic mica-montmorillonite, SWy-2 montmorillonite, NAu-1 and NAu-2 nontronite, and a nontronite from Cheney, Washington (CWN)) was reduced to Fe(II) using the citrate-bicarbonate-dithionite method. Experiments were initiated by adding 500 µM Hg(II) to reduced clay suspensions (4 g clay L−1) buffered at pH 7.2 in 20 mM 3-morpholinopropane-1-sulfonic acid (MOPS). The potential for Hg(II) reduction in the presence of chloride (0–10 mM) and at pH 5–9 was examined in the presence of reduced NAu-1. Analysis of the samples by Hg LIII-edge X-ray absorption fine structure (XAFS) spectroscopy indicated little to no reduction of Hg(II) by SYn-1 (0% Fe), while reduction of Hg(II) to Hg(0) was observed in the presence of reduced SWy-2, NAu-1, NAu-2, and CWN (2.8–24.8% Fe). Hg(II) was reduced to Hg(0) by NAu-1 at all pH and chloride concentrations examined. These results suggest that Fe(II)-bearing smectite clays may contribute to Hg(II) reduction in suboxic/anoxic soils and sediments.

Kinetic analysis of Ag particle redispersion into ZSM-5 in the presence of coke using in situ XAFS

2021 ◽  
Author(s):  
Kazumasa Murata ◽  
Junya Ohyama ◽  
Atsushi Satsuma
Keyword(s):  
Fine Structure ◽  
Kinetic Analysis ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
Ag Particles ◽  
In Situ Xafs ◽  
Ag Particle ◽  
X Ray Absorption

In the present study, the redispersion behavior of Ag particles on ZSM-5 in the presence of coke was observed using in situ X-ray absorption fine structure (XAFS) spectroscopy.

X-Ray Absorption Fine Structure Study in FeTiO3

1997 ◽  
Vol 11 (16n17) ◽  
pp. 745-748 ◽  
Author(s):  
Rebekah Min-Fang Hsu ◽  
Kai-Jan Lin ◽  
Cheng Tien ◽  
Lin-Yan Jang
Keyword(s):  
Absorption Spectrum ◽  
Fine Structure ◽  
Absorption Spectra ◽  
Mixed Valence ◽  
Structure Study ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
Trivalent State ◽  
X Ray Absorption

X-ray absorption fine structure XAFS spectroscopy has been used to determine the valence system for the Fe atom in ilmenite, FeTiO3 . This is the first XAFS data in FeTiO3 to our knowledge. The α- Fe2O3 data served as the standard in determining the ionization of the Fe atom in FeTiO3 . Observation of intensity and k-space are consistent. There was no evidence of mixed valence on comparing the FeTiO3 near edge X-ray absorption spectrum with α- Fe2O3 data. The absorption spectra suggest that iron is in the trivalent state in ilmenite.

scholarly journals Recent progress in the performance of HAPG based laboratory EXAFS and XANES spectrometers

2020 ◽  
Vol 35 (10) ◽  
pp. 2298-2304
Author(s):  
Christopher Schlesiger ◽  
Sebastian Praetz ◽  
Richard Gnewkow ◽  
Wolfgang Malzer ◽  
Birgit Kanngießer
Keyword(s):  
Fine Structure ◽  
Recent Progress ◽  
Pyrolytic Graphite ◽  
New Developments ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
Mosaic Crystals ◽  
X Ray Absorption

New developments in the description and modeling of Highly Annealed Pyrolytic Graphite (HAPG) mosaic crystals have led to the possibility of designing optimized optical solutions for X-ray absorption fine structure (XAFS) spectroscopy.

Oxybarometry and valence quantification based on microscale X-ray absorption fine structure (XAFS) spectroscopy of multivalent elements

2020 ◽  
Vol 531 ◽  
pp. 119305 ◽  
Author(s):  
S.R. Sutton ◽  
A. Lanzirotti ◽  
M. Newville ◽  
M. Darby Dyar ◽  
J. Delaney
Keyword(s):  
Fine Structure ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
X Ray Absorption

scholarly journals DAFNE-Light DXR1 Soft X-Ray Synchrotron Radiation Beamline: Characteristics and XAFS Applications

2019 ◽  
Vol 4 (1) ◽  
pp. 7 ◽  
Author(s):  
Antonella Balerna
Keyword(s):  
Fine Structure ◽  
Synchrotron Radiation ◽  
Disordered Systems ◽  
Beam Line ◽  
Long Range Order ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Insertion Device ◽  
Different Types ◽  
X Ray Absorption

X-ray Absorption Fine Structure Spectroscopy (XAFS) is a powerful technique to investigate the local atomic geometry and the chemical state of atoms in different types of materials, especially if lacking a long-range order, such as nanomaterials, liquids, amorphous and highly disordered systems, and polymers containing metallic atoms. The INFN-LNF DAΦNE-Light DXR1 beam line is mainly dedicated to soft X-ray absorption spectroscopy; it collects the radiation of a wiggler insertion device and covers the energy range from 0.9 to 3.0 keV or the range going from the K-edge of Na through to the K-edge of Cl. The characteristics of the beamline are reported here together with the XAFS spectra of reference compounds, in order to show some of the information achievable with this X-ray spectroscopy. Additionally, some examples of XAFS spectroscopy applications are also reported.

Bent crystal Laue analyser combined with total reflection fluorescence X-ray absorption fine structure (BCLA + TRF-XAFS) and its application to surface studies

2020 ◽  
Vol 27 (6) ◽  
pp. 1618-1625
Author(s):  
Yuki Wakisaka ◽  
Bing Hu ◽  
Daiki Kido ◽  
Md. Harun Al Rashid ◽  
Wenhan Chen ◽  
...  
Keyword(s):  
Fine Structure ◽  
Sudden Change ◽  
Fluorescence Emission ◽  
Total Reflection ◽  
X Rays ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Bent Crystal ◽  
Absorption Fine ◽  
X Ray Absorption

A bent crystal Laue analyser (BCLA) is an X-ray energy analyser used for fluorescence X-ray absorption fine-structure (XAFS) spectroscopy to separate the fluorescence X-ray emission line of a target atom from the elastic scattering X-rays and other fluorescence emission lines. Here, the feasibility of the BCLA for total reflection fluorescence XAFS (TRF-XAFS), which has a long X-ray footprint on the substrate surface owing to grazing incidence, was tested. The focal line of the BCLA was adjusted on the X-ray footprint and the XAFS signal for one monolayer of Pt deposited on a 60 nm Au film with high sensitivity was obtained. Although range-extended XAFS was expected by the rejection of Au fluorescence arising from the Au substrate, a small glitch was found in the Au L 3 edge because of the sudden change of the complex refraction index of the Au substrate at the Au edge. This abnormal spectrum feature can be removed by reflectivity correction using Au foil absorption data. BCLA combined with TRF-XAFS spectroscopy (BCLA + TRF-XAFS) is a new technique for the in situ surface analysis of highly dispersed systems even in the presence of a liquid overlayer.

scholarly journals The Structure of Actinide Ions Exchanged into Native and Modified Zeolites and Clays

1999 ◽  
Vol 590 ◽  
Author(s):  
Stephen R. Wasserman ◽  
L. Soderholm ◽  
Daniel M. Giaquinta
Keyword(s):  
Pore Size ◽  
Organic Films ◽  
Mineral Surface ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Chemical Fate ◽  
Smectite Clays ◽  
Modified Zeolites ◽  
X Ray Absorption ◽  
Actinide Ions

ABSTRACTx-ray absorption spectroscopy (XAS) has been used to investigate the structure and valence of thorium (Th4+) and uranyl () cations exchanged into two classes of microporous aluminosilicate minerals: zeolites and smectite clays. XAS is also employed to examine the fate of the exchanged cations after modification of the mineral surface using self-assembled organic films and/or exposure to hydrothermal conditions. These treatments serve as models for the forces that ultimately determine the chemical fate of the actinide cations in the environment. The speciation of the cations depends on the pore size of the aluminosilicate, which is fixed for the zeolites and variable for the smectites.

Sign in / Sign up

Export Citation Format

Share Document