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.

X-ray-absorption sum rules injj-coupled operators and ground-state moments of actinide ions

1996 ◽  
Vol 53 (21) ◽  
pp. 14458-14469 ◽  
Author(s):  
Gerrit van der Laan ◽  
B. T. Thole
Keyword(s):  
Ground State ◽  
Sum Rules ◽  
X Ray ◽  
X Ray Absorption ◽  
Actinide Ions

In Situ X-ray Absorption Spectroscopy Study of Si1–xGexO2 Dissolution and Germanium Aqueous Speciation under Hydrothermal Conditions

2011 ◽  
Vol 51 (1) ◽  
pp. 414-419 ◽  
Author(s):  
V. Ranieri ◽  
J. Haines ◽  
O. Cambon ◽  
C. Levelut ◽  
R. Le Parc ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Spectroscopy Study ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
X Ray Absorption

Structure of aqueous ZnBr2 solution probed by x-ray absorption spectroscopy in normal and hydrothermal conditions

2002 ◽  
Vol 116 (7) ◽  
pp. 2997-3006 ◽  
Author(s):  
V. Simonet ◽  
Y. Calzavara ◽  
J. L. Hazemann ◽  
R. Argoud ◽  
O. Geaymond ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
X Ray Absorption

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.

In situ X-ray absorption spectroscopy measurement of vapour-brine fractionation of antimony at hydrothermal conditions

2008 ◽  
Vol 72 (2) ◽  
pp. 667-681 ◽  
Author(s):  
G. S. Pokrovski ◽  
J. Roux ◽  
J.-L. Hazemann ◽  
A. YU. Borisova ◽  
A. A. Gonchar ◽  
...  
Keyword(s):  
Salt Water ◽  
Batch Reactor ◽  
Total Concentration ◽  
Hydrothermal Systems ◽  
Hydrothermal Conditions ◽  
Geological Evidence ◽  
X Ray ◽  
Liquid Phases ◽  
X Ray Absorption

AbstractDespite the growing geological evidence that fluid boiling and vapour-liquid separation affect the distribution of metals in magmatic-hydrothermal systems significantly, there are few experimental data on the chemical status and partitioning of metals in the vapour and liquid phases. Here we report on an in situ measurement, using X-ray absorption fine structure (XAFS) spectroscopy, of antimony speciation and partitioning in the system Sb2O3-H2O-NaCl-HCl at 400°C and pressures 270—300 bar corresponding to the vapour-liquid equilibrium. Experiments were performed using a spectroscopic cell which allows simultaneous determination of the total concentration and atomic environment of the absorbing element (Sb) in each phase. Results show that quantitative vapour-brine separation of a supercritical aqueous salt fluid can be achieved by a controlled decompression and monitoring the X-ray absorbance of the fluid phase. Antimony concentrations in equilibrium with Sb2O3 (cubic, senarmontite) in the coexisting vapour and liquid phases and corresponding SbIII vapour-liquid partitioning coefficients are in agreement with recent data obtained using batch-reactor solubility techniques. The XAFS spectra analysis shows that hydroxy-chloride complexes, probably Sb(OH)2Cl0, are dominant both in the vapour and liquid phase in a salt-water system at acidic conditions. This first in situ XAFS study of element fractionation between coexisting volatile and dense phases opens new possibilities for systematic investigations of vapour-brine and fluid-melt immiscibility phenomena, avoiding many experimental artifacts common in less direct techniques.

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