Compositional dependence of redox equilibria in sodium silicate glasses

Schreiber, Henry D.; Kochanowski, Brian K.; Schreiber, Charlotte W.; Morgan, Alexander B.; Coolbaugh, M. T.; Dunlap, Teresa G.

doi:10.1016/0022-3093(94)90548-7

Cited by 60 publications

(55 citation statements)

References 10 publications

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“…In synthetic melt glasses, Fe acts as a buffer for U [40][41][42]. However, the Event 3 glass in the present study contains more reduced Fe and oxidized U in comparison with the Event 1 and Event 2 glasses.…”

Section: Discussioncontrasting

confidence: 46%

“…Specifically, the Fe(II)/Fe(III) ratio in melt glass is generally higher than in the surrounding rock and soil. It is also important to note that transition metals, including Fe, can act as buffers for the redox state of U and Pu in silicate glasses [40][41][42]. To our knowledge, the only further studies in this direction have been two evaluations of Fe oxidation states in fallout glass from the Trinity site [43,44] and a comparison of Fe and U oxidation states in synthetic melt glasses with specimens collected from the NNSS [30].…”

Section: Introductionmentioning

confidence: 99%

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Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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Nuclear weapons testing generates large volumes of glassy material that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variations among the melt glass samples, and in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry, and the later environmental mobility of dispersed material.

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Section: Discussioncontrasting

confidence: 46%

Section: Introductionmentioning

confidence: 99%

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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“…A similar trend to that which we have noted, i. /ΣCu ratio of P2O5-CuO-(Cu2O) glasses as a function of CuO content by a number of independent research groups [66], [67], [68] and [69]. Some authors have, like Schreiber et al [67], attempted to explain this behavior by a change in transition metal ion coordination as a function of glass composition [70] and [71].…”

Section: Fe Mössbauer Spectroscopysupporting

confidence: 54%

“…6(b)). In some cases, changing glass basicity does not adequately explain the redox behavior in glasses of iron [66] and [67] and certain other multivalent species [68], [69], [70], [71] and [72]. Others have also noted that redox behavior may involve other factors than glass basicity [63] and [65].…”

Section: Fe Mössbauer Spectroscopymentioning

confidence: 99%

Effects of modifier additions on the thermal properties, chemical durability, oxidation state and structure of iron phosphate glasses

Bingham

Hand

Hannant

et al. 2009

Journal of Non-Crystalline Solids

172

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Modified iron phosphate glasses have been prepared with nominal molar compositions [(1−x)·(0.6P2O5-0.4Fe2O3)]·xRySO4, where x = 0-0.5 in increments of 0.1 and R = Li, Na, K, Mg, Ca, Ba, or Pb and y = 1 or 2. In most cases the vast majority or all of the sulfate volatalizes and quarternary P2O5-Fe2O3-FeO-RyOz glasses or partially crystalline materials are formed. Here we have characterized the structure, thermal properties, chemical durability and redox state of these materials. Raman spectroscopy indicates that increasing modifier oxide additions result in depolymerization of the phosphate network such that the average value of i, the number of bridging oxygens per -(PO4)-tetrahedron, and expressed as Q i , decreases. Differences have been observed between the structural effects of different modifier types but these are secondary to the amount of modifier added. Alkali additions have little effect on density; slightly increasing Tg and Td; increasing α and Tliq; and promoting bulk crystallization at temperatures of 600-700 °C.Additions of divalent cations increase density, α, Tg, Td, Tliq and promote bulk crystallization at temperatures of 700-800 °C. Overall the addition of divalent cations has a less deleterious effect on glass stability than alkali additions.57 FeMössbauer spectroscopy confirms that iron is present as Fe 2+ and Fe 3+ ions which primarily occupy distorted octahedral sites. This is consistent with accepted structural models for iron phosphate glasses. The iron redox ratio, Fe 2+/ΣFe, has a value of 0.13-0.29 for the glasses studied. The base glass exhibits a very low aqueous leach rate when measured by Product Consistency Test B, a standard durability test for nuclear waste glasses. The addition of high quantities of alkali oxide (30-40 mol% R2O) to the base glass increases leach rates, but only to levels comparable with those measured for a commercial soda-lime-silica glass and for a surrogate nuclear waste-loaded borosilicate glass. Divalent cation additions decrease aqueous leach rates and large additions (30-50 mol% RO) provide exceptionally low leach rates that are 2-3 orders of magnitude lower than have been measured for the surrogate waste-loaded borosilicate glass. The P2O5-Fe2O3-FeO-BaO glasses reported here show particular promise as they are ultra-durable, thermally stable, lowmelting glasses with a large glass-forming compositional range.

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“…At a given melting condition, the redox couple shis towards the oxidized state when modier ions or glass basicity are increased. 7 Mn in glasses may be expected to be in the form of MnO . The content and valence states of Mn in various environments in the glasses are dependent on quantitative properties of modiers and glass formers, size of the ions in the glass structure, their eld strength, mobility of the modier cation, etc.…”

Section: -Mnmentioning

confidence: 99%