![]() Harvey, “History of the Hanford Site: 1943–1990”, PNNL-SA-33307, Pacific Northwest National Laboratory. ![]() Apparently, the details of incorporation of Cr, and to an extent V, are different depending on whether sulfur is added as in this study or in oversaturated conditions as described in the literature, where Cr partitions to a sulfate-containing salt phase. A fraction of batched S was not incorporated in any glass, presumably due to volatilization during melting. On the other hand, all the targeted V was incorporated into the glass. Increasing Cr 2O 3 caused saturation of Cr concentration within the glass and formation of crystalline eskolaite (Cr 2O 3). Electron probe microanalysis determined elemental compositions to assess retention of components. Both Cr 6+ (CrO 4 2−) and Cr 3+ were found in the chromium-containing glasses while vanadium primarily existed in the 5+ oxidation state in the vanadium-containing glasses. Glass transition temperature, mass density, visible absorption, and Raman scattering were measured to investigate changes in the glass structure. ![]() The aim of the current study is to understand how vanadium and chromium each affect a sulfate-containing sodium aluminoborosilicate glass structure. In particular, certain elements identified in previous studies tend to raise or lower sulfate solubility in borosilicate glass. 12 references, 6 figures, 1 table.In the composition space for Hanford low-activity nuclear waste glass, the waste loading of some formulations is limited by poor incorporation of sulfate. A general relationship (log (CrOH/sup 2 +/) = -2pH + 4.18 + 0.28(1 - x)/sup 2/ - 1.79(1 - x)/sup 3/ + log x) developed from these data can be used to calculate Cr concentrations in solutions between pH 2 and 6 that are in equilibrium with Cr-bearing ferric hydroxides with known Cr content. Aqueous Fe activities were generally too low for reliable measurement more » therefore, the corresponding activity coefficients for Fe(OH)/sub 3/ (log lambda/sub Fe(OH)3/ = -2.26x/sup 2/ + 1.39x/sup 3/) were calculated by a Gibbs-Duhem equation. Activity coefficients for Cr(OH)/sub 3/ in the solid solutions were calculated from the solubility data and are given by the equation log lambda/sub Cr(OH)3/ = -1.60 + 0.28(1 - x)/sup 2/ - 1.79(1 - x)/sup 3/ for 0.01 less than or equal to x less than or equal to 0.69. In general, aqueous Cr concentrations decrease with decreasing Cr contents in the solids, suggesting that Cr/sub x/Fe/sub 1-x/(OH)/sub 3/ behaves thermodynamically like a solid solution. The Cr concentrations in 0.0018-.mu.m filtrates at various times between 5 and 210 days, from initially undersaturated and oversaturated solutions, show that equilibrium was attained within about 7 days when x < 0.5 and more slowly when higher mole fractions of Cr(OH)/sub 3/ were used. The solubilities of the Cr/sub x/Fe/sub 1-x/(OC)/sub 3/ precipitates prepared with different mole fractions (x) of Cr(OH)/sub 3/ (0.99, 0.89, 0.69, 0.49, 0.36, 0.15, 0.09, 0.01, 0.00) were determined in 0.01 M prechlorate solutions between pH 2 and 6 in an N/sub 2/ atmosphere. ![]() Neutralization of acidic solutions containing Cr(III) and Fe(III) at room temperatures results in coprecipitation of these elements as an amorphous solid solution (Cr/sub x/Fe/sub 1-x/(OH)/sub 3/). ![]()
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