Study of the Oxidation State of Arsenic and Uranium in Individual Particles From Uranium Mine Tailings, Hungary

2007 ◽  
Author(s):  
A. Alsecz ◽  
J. Osa´n ◽  
J. Pa´lfalvi ◽  
I. Sajo´ ◽  
Z. Ma´the´ ◽  
...  
Keyword(s):  
Oxidation State ◽  
Mine Tailings ◽  
Track Detector ◽  
Uranium Mine ◽  
Nuclear Track Detector ◽  
Mobile Form ◽  
Edge Structure ◽  
X Ray ◽  
Uranium Ore ◽  
Distribution Of Elements

Uranium ore mining and milling have been terminated in the Mecsek Mountains (southwest Hungary) in 1997. Mine tailings ponds are located between two important water bases, which are resources of the drinking water of the city of Pe´cs and the neighbouring villages. The average U concentration of the tailings material is 71.73 μg/g, but it is inhomogeneous. Some microscopic particles contain orders of magnitude more U than the rest of the tailings material. Other potentially toxic elements are As and Pb of which chemical state is important to estimate mobility, because in mobile form they can risk the water basis and the public health. Individual U-rich particles were selected with solid state nuclear track detector (SSNTD) and after localisation the particles were investigated by synchrotron radiation based microanalytical techniques. The distribution of elements over the particles was studied by micro beam X-ray fluorescence (μ-XRF) and the oxidation state of uranium and arsenic was determined by micro X-ray absorption near edge structure (μ-XANES) spectroscopy. Some of the measured U-rich particles were chosen for studying the heterogeneity with μ-XRF tomography. Arsenic was present mainly in As(V) and uranium in U(VI) form in the original uranium ore particles, but in the mine tailings samples uranium was present mainly in the less mobile U(IV) form. Correlation was found between the oxidation state of As and U in the same analyzed particles. These results suggest that dissolution of uranium is not expected in short term period.

Oxygen Reduction Effect on T’-Pr2-xCexCuO4 Nanopowders in the Underdoped Regime Studied by X-Ray Absorption near Edge Structure

2018 ◽  
Vol 936 ◽  
pp. 93-97 ◽  
Author(s):  
Irfanita Resky ◽  
Putu Eka Dharma Putra ◽  
Triono Bambang ◽  
Saiyasombat Chatree ◽  
Kamonsuangkasem Krongthong ◽  
...  
Keyword(s):  
Oxidation State ◽  
Oxidation States ◽  
Edge Structure ◽  
X Ray ◽  
Reduction Annealing ◽  
Gas Atmosphere ◽  
Reduction Effect ◽  
Ar Gas ◽  
X Ray Absorption ◽  
Cu Ions

This research is aimed to examine oxidation state of Copper (Cu) in both as-synthesized and reduced T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0, 0.10, and 0.15 using Cu K-edge x-ray absorption near edge structure (XANES). The T‘-PCCO nanopowders were successfully synthesized by the chemically dissolved method with HNO3 as a dissolving agent continued by calcination at 1000°C for 15 h. The reduced T’-PCCO nanopowders were obtained by reduction annealing process at 700°C for 5 h under Ar gas atmosphere. The analyses of XANES spectra show that oxidation states of the Cu ions in all of the T'-PCCO nanopowders have values between +1 and +2. This indicates the existence of electron doping in the CuO2 planes, even in the undoped T’-structure. It is found that the oxidation states of the Cu ions change after reduction annealing depending on the existence of apical oxygen in the T'-structure. Based on the XANES analyses, it is revealed that the change of oxidation state is influenced by the presence of both electron and hole carriers in the two-carrier model of T’-structure.

Using X-ray absorption near edge structure (XANES) spectroscopy to determine selenium oxidation states in animal mineral supplements and feeds

2004 ◽  
Vol 84 (2) ◽  
pp. 171-175 ◽  
Author(s):  
C. R. Christensen ◽  
J. N. Cutler ◽  
D. A. Christensen
Keyword(s):  
Oxidation State ◽  
Animal Feed ◽  
Xanes Spectroscopy ◽  
Elemental Selenium ◽  
Selenium Speciation ◽  
Edge Structure ◽  
X Ray ◽  
Mineral Supplements ◽  
Animal Feeds ◽  
X Ray Absorption

Synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy is a relatively new technique within the life sciences. XANES has been utilized to identify the location, oxidation state and spatial distribution of heavy metal elements in plants , neurons, blood and DNA, but has not been widely used in the animal sciences. Selenium content in animal feeds is monitored, as both selenium deficiencies and toxicities are associated with physiological disorders. Selenium is available as an animal feed in both inorganic and organic states. The bioavailability of selenium species has been tested in numerous animal trials; however, a simple, non-destructive test for selenium speciation is not available. The objective of this study was to determine whether XANES spectroscopy could be used to determine the selenium oxidation state found in various commercial animal feed products. A comparison of absorption spectra indicated that the animal mineral supplements contained an organoselenium or selenite. The processed animal feeds had a spectral profile similar to that of elemental selenium. Further experiments are necessary to determine the implication of selenium speciation on animal physiology. Key words: Selenium speciation, mineral supplements, ruminants, non-ruminants, synchrotron, XANES, X-ray

Oxidation State of Ti Atoms and Ti-O Bond Length on Natural Sapphire Gem-Materials Probed by X-Ray Absorption Spectroscopy

2017 ◽  
Vol 737 ◽  
pp. 585-589 ◽  
Author(s):  
Natthapong Monarumit ◽  
Wiwat Wongkokua ◽  
Somruedee Satitkune
Keyword(s):  
Bond Length ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Germanium Detector ◽  
Blue Color ◽  
Edge Structure ◽  
X Ray ◽  
Fe Content ◽  
X Ray Absorption ◽  
Exafs Spectra

Sapphire, an inorganic gem-material in a variety of corundum, mainly consists of alpha-alumina (α-Al2O3) structure. The geological origins of sapphire are related to either basaltic or metamorphic rocks. The causes of the color on sapphire are some trace elements such as Cr, Fe, and Ti. It could be mentioned that Ti atoms have cooperated with Fe atoms for creating the blue color. In this study, X-ray absorption spectroscopy (XAS) technique focused on the x-ray absorption near edge structure (XANES) and the extended x-ray absorption fine structure (EXAFS) is employed to identify the oxidation state of Ti atoms and Ti-O bond length on sapphire samples. The Ti K-edge XANES and EXAFS spectra of natural sapphires were carried out using the 13-channel array germanium detector in fluorescence mode. The XANES spectra showed that the oxidation state of Ti was Ti4+ regardless of Fe content. Moreover, the Ti-O bond length on a-Al2O3 was equal to the Ti-O bond length on rutile (TiO2) analyzed from the EXAFS spectra. From these results, it could be concluded that the oxidation state of Ti atoms on natural sapphires was Ti4+ which substitutes Al3+ on the sapphire structure.

Direct determination of oxidation state of gold deposits in metal-reducing bacterium Shewanella algae using X-ray absorption near-edge structure spectroscopy (XANES)

2007 ◽  
Vol 103 (6) ◽  
pp. 568-571 ◽  
Author(s):  
Yasuhiro Konishi ◽  
Takeshi Tsukiyama ◽  
Norizoh Saitoh ◽  
Toshiyuki Nomura ◽  
Shinsuke Nagamine ◽  
...  
Keyword(s):  
Oxidation State ◽  
Direct Determination ◽  
Gold Deposits ◽  
Edge Structure ◽  
X Ray ◽  
Shewanella Algae ◽  
X Ray Absorption

Arsenic and iron speciation in uranium mine tailings using X-ray absorption spectroscopy

2013 ◽  
Vol 28 ◽  
pp. 11-18 ◽  
Author(s):  
Joseph Essilfie-Dughan ◽  
M. Jim Hendry ◽  
Jeff Warner ◽  
Tom Kotzer
Keyword(s):  
Absorption Spectroscopy ◽  
Mine Tailings ◽  
Uranium Mine ◽  
Iron Speciation ◽  
X Ray ◽  
X Ray Absorption

scholarly journals A compact furnace for in situ X-ray absorption spectroscopy: design, fabrication and study of cationic oxidation states in Pr6O11 and NiO

2021 ◽  
Vol 28 (2) ◽  
pp. 455-460
Author(s):  
Suchinda Sattayaporn ◽  
Somboonsup Rodporn ◽  
Pinit Kidkhunthod ◽  
Narong Chanlek ◽  
Chutarat Yonchai ◽  
...  
Keyword(s):  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Heating Temperature ◽  
Reduction Process ◽  
Oxidation States ◽  
Quartz Tube ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

A well designed compact furnace has been designed for in situ X-ray absorption spectroscopy (XAS). It enables various heat ramps from 300 K to 1473 K. The furnace consists of heaters, a quartz tube, a circulated refrigerator and a power controller. It can generate ohmic heating via an induction process with tantalum filaments. The maximum heating rate exceeds 20 K min−1. A quartz tube with gas feedthroughs allows the mixing of gases and adjustment of the flow rate. The use of this compact furnace allows in situ XAS investigations to be carried out in transmission or fluorescence modes under controlled temperature and atmosphere. Moreover, the furnace is compact, light and well compatible to XAS. The furnace was used to study cationic oxidation states in Pr6O11 and NiO compounds under elevated temperature and reduced atmosphere using the in situ X-ray absorption near-edge structure (XANES) technique at beamline 5.2 SUT-NANOTEC-SLRI of the Synchrotron Light Research Institute, Thailand. At room temperature, Pr6O11 contains a mixture of Pr3+ and Pr4+ cations, resulting in an average oxidation state of +3.67. In situ XANES spectra of Pr (L 3-edge) show that the oxidation state of Pr4+ cations was totally reduced to +3.00 at 1273 K under H2 atmosphere. Considering NiO, Ni2+ species were present under ambient conditions. At 573 K, the reduction process of Ni2+ occurred. The Ni0/Ni2+ ratio increased linearly with respect to the heating temperature. Finally, the reduction process of Ni2+ was completely finished at 770 K.

scholarly journals The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 640 ◽  
Author(s):  
Nikolay D. Trofimov ◽  
Alexander L. Trigub ◽  
Boris R. Tagirov ◽  
Olga N. Filimonova ◽  
Polina V. Evstigneeva ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Atomic Structure ◽  
Salt Flux ◽  
Ionic Radii ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Exafs Spectra

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.

EELS and Xanes Analysis of Plutonium and Cerium Edges From Titanate Ceramics for Fissile Materials Disposal

1999 ◽  
Vol 5 (S2) ◽  
pp. 768-769
Author(s):  
J.A. Fortner ◽  
E.C. Buck ◽  
A.J. Kropf ◽  
A.J. Bakel ◽  
M.C. Hash ◽  
...  
Keyword(s):  
Oxidation State ◽  
Electron Loss ◽  
Edge Structure ◽  
X Ray ◽  
Titanate Ceramics ◽  
X Ray Absorption ◽  
Photon Source ◽  
Titanate Ceramic ◽  
Exafs Spectra

We report x-ray absorption near edge structure (XANES) and extended x-ray fine structure analysis (EXAFS) spectra from the plutonium Llll and cerium Lm edges in prototype titanate ceramic hosts for disposal of surplus fissile materials. These spectra were obtained using the MRCAT beamline at the Advanced Photon Source (APS). The XANES and EXAFS results are compared with electron loss spectra (EELS) determination of oxidation state from the plutonium MlV,V and cerium MlV,V edges [1,2]. The titanate ceramics studied are based upon the hafniumpyrochlore and zirconolite mineral structures and will serve as an immobilization host, containing as much as 10 weight % fissile plutonium, and 20 weight % (natural or depleted) uranium. Similar formulations were composed using cerium as a “surrogate” element, replacing both plutonium and uranium in the ceramic matrix. We find the plutonium to be present almost entirely as Pu (IV), while the cerium is clearly in a mixed III-IV oxidation state in the surrogate ceramic.

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