Investigation of the Redox Behavior of Technetium in Borosilicate Glass Melts by Voltammetry

1988 ◽  
Vol 127 ◽  
Author(s):  
E. Freude ◽  
W. Lutze ◽  
C. Rüssel ◽  
H. A. Schaeffer
Keyword(s):  
Borosilicate Glass ◽  
Redox Reactions ◽  
Electrochemical Measurements ◽  
Redox Behavior ◽  
Glass Melts ◽  
Reducing Conditions ◽  
Waste Vitrification ◽  
T State

ABSTRACTTechnetium is a potentially hazardous radionuclide in the waste vitrification process as its oxides are volatile. Electrochemical measurements, i.e. potentiometry and voltammetry are applied to investigate the redox reactions of Tc in the glass melt. Re is studied for comparison. Under normal oxidizing conditions Tc is in the -T-state, and substancial losses of Tc occur as a result of compound volatility. Reducing conditions lead to the formation of TcO2, which precipitates from the melt. Stronger reducing conditions lead to the formation of metallic Tc

scholarly journals Electron Inventory of the Iron-Sulfur Scaffold Complex HypCD Essential in [NiFe]-Hydrogenase Cofactor Assembly

2021 ◽  
Author(s):  
Sven T. Stripp ◽  
Jonathan Oltmanns ◽  
Christina S. Müller ◽  
David Ehrenberg ◽  
Ramona Schlesinger ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Redox Activity ◽  
Construction Site ◽  
Iron Ion ◽  
Paramagnetic Resonance ◽  
Iron Sulfur ◽  
Reducing Conditions ◽  
Reversible Redox ◽  
Electron Paramagnetic ◽  
Redox Conversion

The [4Fe-4S] cluster containing scaffold complex HypCD is the central construction site for the assembly of the [Fe](CN)2CO cofactor precursor of [NiFe]-hydrogenase. While the importance of the HypCD complex is well established, not much is known about the mechanism by which the CN– and CO ligands are transferred and attached to the iron ion. We developed an efficient protocol for the production and isolation of the functional HypCD complex that facilitated detailed spectroscopic investigations. The results obtained by UV/Vis-, electron paramagnetic Resonance (EPR)-, Resonance Raman-, Fourier-transform infrared (FTIR), and Mössbauer spectroscopy provide comprehensive evidence for an electron inventory fit to drive multi-electron redox reactions. We demonstrate the redox activity of the HypCD complex reporting the interconversion of the [4Fe-4S]2+/+ couple. Additionally, we observed a reversible redox conversion between the [4Fe-4S]2+ and a [3Fe-4S]+ cluster. MicroScale thermophoresis indicated preferable binding between the HypCD complex and its interaction partner HypEF under reducing conditions. Together, these results suggest a redox cascade involving the [4Fe-4S] cluster and a conserved disulfide bond of HypD that may facilitate the synthesis of the [Fe](CN)2CO cofactor precursor on the HypCD scaffold complex.

Nitrogen and Argon in Borosilicate Glass: Solubility, Diffusivity, Residual Gas Concentration and Behaviour of Bubbles in Glass Melts, Containing Both Gases

2008 ◽  
Vol 39-40 ◽  
pp. 437-442 ◽  
Author(s):  
Detlef Köpsel ◽  
Markus Booβ ◽  
M. Opyd ◽  
Maria Louisa Aigner
Keyword(s):  
High Temperature ◽  
Gas Exchange ◽  
Borosilicate Glass ◽  
Diffusion Coefficients ◽  
Molten Glass ◽  
Extraction Method ◽  
Vacuum Extraction ◽  
Glass Melts ◽  
Gas Concentration ◽  
Residual Gas

Diffusivities of nitrogen and argon in a borosilicate glass were determined with two different methods: (1) from gas exchange experiments between molten glass and bubbles containing nitrogen and argon, and (2) from solution rates of nitrogen and argon in glass during saturation experiments. Between 1200°C and 1580°C the diffusion coefficients of nitrogen and argon yielded the following equations:      − = − RT s m DN 134900 exp 10 22 . 1 ] / [ 6 . 2 2 and      − = − RT s m DAr 125300 exp 10 08 . 1 ] / [ 6 . 2 , with R=8.314 J/(mol.K). The solubilities and residual gas concentration in the glass which are necessary for the calculation of the diffusivities were determined with the high temperature vacuum extraction method.

Pyren-1-ylmethyl N-substituted oxoporphyrinogens

2007 ◽  
Vol 11 (05) ◽  
pp. 390-396 ◽  
Author(s):  
Jonathan P. Hill ◽  
Katsuhiko Ariga ◽  
Amy Lea Schumacher ◽  
Paul A. Karr ◽  
Francis D'Souza
Keyword(s):  
Electrochemical Properties ◽  
Electrochemical Measurements ◽  
Redox Behavior ◽  
Tert Butyl ◽  
Reversible Redox ◽  
Excimer Formation

5,10,15,20-tetrakis(3,5-di-tert-butyl-4-oxocyclohexadien-2,5-yl)porphyrinogen was alkylated at its macrocyclic nitrogen atoms with pyren-1-ylmethyl groups and the effect of increasing N-substitution on the spectroscopic and electrochemical properties was investigated. Both pyrene and oxoporphyrinogen chromophores exhibit fluorescence and there is little interaction between them except in the higher N-substituted compounds. Intra- or intermolecular excimer formation by pyrene is precluded by attachment to the bulky oxoporphyrinogen. Electrochemical measurements revealed reversible redox behavior.

Initial Investigation Into the Vitrification of High Molybdenum Solids in Borosilicate Glass

2009 ◽  
Vol 1193 ◽  
Author(s):  
Barbara F. Dunnett ◽  
Nick R. Gribble ◽  
Andrew D. Riley ◽  
Carl J. Steele
Keyword(s):  
Phase Separation ◽  
Borosilicate Glass ◽  
Spent Nuclear Fuel ◽  
Storage Tanks ◽  
Waste Storage ◽  
Waste Vitrification ◽  
Durability Testing ◽  
Glass Formulation ◽  
Selection Of ◽  
Scanning Electron

AbstractSellafield Ltd operates a Waste Vitrification Plant (WVP) to immobilise the arisings from the reprocessing of spent nuclear fuel. Washout of solids from the base of waste storage tanks in preparation for decommissioning is likely to produce feeds enriched in molybdenum to the WVP. Vitrification of such feeds in the borosilicate glass formulation currently used by the WVP for vitrification of reprocessing waste has been investigated to determine the maximum achievable loading of MoO3.The vitrification of molybdenum in the absence and presence of reprocessing waste was studied. A number of glasses were manufactured in the laboratory containing various waste loadings. The resultant glasses were examined both visually and under the scanning electron microscope for the presence of any phase separation. Additional aluminium was added to the glasses manufactured in the absence of reprocessing waste to improve the durability of the glass. In borosilicate glass containing 3.5 wt% Al2O3 the onset of a molybdenum phase separation was observed in glasses containing 2.6 wt% MoO3. In the presence of Magnox reprocessing waste, phase separation was observed when the product contained >3.8 wt% MoO3. Soxhlet durability testing of a selection of the glasses manufactured was carried out. The Soxhlet durability of glasses in the absence of phase separation was good.

Redox behavior of Tc(VII)/Tc(IV) under various reducing conditions in 0.1 M NaCl solutions

2013 ◽  
Vol 101 (5) ◽  
pp. 323-332 ◽  
Author(s):  
Taishi Kobayashi ◽  
Andreas C. Scheinost ◽  
D. Fellhauer ◽  
Xavier Gaona ◽  
Marcus Altmaier
Keyword(s):  
Redox Behavior ◽  
Reducing Conditions

scholarly journals Interaction of Corroding Iron with Eight Bentonites in the Alternative Buffer Materials Field Experiment (ABM2)

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 907
Author(s):  
Paul Wersin ◽  
Jebril Hadi ◽  
Andreas Jenni ◽  
Daniel Svensson ◽  
Jean-Marc Grenèche ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Hard Rock ◽  
High Spatial Resolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rock Laboratory ◽  
Reducing Conditions ◽  
Buffer Material ◽  
High Level ◽  
Redox Evolution

Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by “bulk” methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found.

scholarly journals Electron Inventory of the Iron-Sulfur Scaffold Complex HypCD Essential in [NiFe]-Hydrogenase Cofactor Assembly

2021 ◽  
Author(s):  
Sven T. Stripp ◽  
Jonathan Oltmanns ◽  
Christina S. Müller ◽  
David Ehrenberg ◽  
Ramona Schlesinger ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Redox Activity ◽  
Construction Site ◽  
Iron Ion ◽  
Paramagnetic Resonance ◽  
Iron Sulfur ◽  
Reducing Conditions ◽  
Reversible Redox ◽  
Electron Paramagnetic ◽  
Redox Conversion

The [4Fe-4S] cluster containing scaffold complex HypCD is the central construction site for the assembly of the [Fe](CN)2CO cofactor precursor of [NiFe]-hydrogenase. While the importance of the HypCD complex is well established, not much is known about the mechanism by which the CN– and CO ligands are transferred and attached to the iron ion. We developed an efficient protocol for the production and isolation of the functional HypCD complex that facilitated detailed spectroscopic investigations. The results obtained by UV/Vis-, electron paramagnetic Resonance (EPR)-, Resonance Raman-, Fourier-transform infrared (FTIR), and Mössbauer spectroscopy provide comprehensive evidence for an electron inventory fit to drive multi-electron redox reactions. We demonstrate the redox activity of the HypCD complex reporting the interconversion of the [4Fe-4S]2+/+ couple. Additionally, we observed a reversible redox conversion between the [4Fe-4S]2+ and a [3Fe-4S]+ cluster. MicroScale thermophoresis indicated preferable binding between the HypCD complex and its interaction partner HypEF under reducing conditions. Together, these results suggest a redox cascade involving the [4Fe-4S] cluster and a conserved disulfide bond of HypD that may facilitate the synthesis of the [Fe](CN)2CO cofactor precursor on the HypCD scaffold complex.

Sign in / Sign up

Export Citation Format

Share Document