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Title: Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory

Abstract

Abstract—The dissolution kinetics of five chemically complex and two chemically simple borosilicate glass compositions (Na-B-Si±Al) were determined over a range of solution saturation values by varying the flow-through rates (1 to 100 mL d -1) in a dynamic single-pass flow-through (SPFT) apparatus. The chemically complex borosilicate glasses are representative of prospective hosts for radioactive waste disposal and are characterized by relatively high molar Si/(Si+Al) and Na/(Al+B) ratios (>0.7 and >1.0, respectively). Analysis by x-ray absorption spectroscopy (XAS) indicates that the fraction of ivB to iiiB (N 4) varies from 0.66 to 0.70. Despite large differences in bulk chemistry, values of δ 29Si peak shift determined by MAS-NMR varies only by about 7 ppm (δ 29Si = -94 to -87 ppm), indicating small differences in polymerization state for the glasses. Forward rates of reaction measured in dynamic experiments converge (average log10 rate [40°C, pH 9] = -1.87±0.79 [g/(m 2•d)]) at high values of flow-rate (q) to sample surface area (S). Dissolution rates are independent of total Free Energy of Hydration (FEH) and this model appears to overestimate the impact of excess Na on chemical durability. For borosilicate glass compositions in which molar Na > Al + B, further addition of Namore » appears to stabilize the glass structure with respect to hydrolysis and dissolution. Compared to other borosilicate and aluminosilicate glasses, the glass specimens from this study dissolve at nearly the same rate (0 to ~55×) as the more polymerized glasses, such as vitreous reedmergnerite (NaBSi3O8), albite, and silica. Dissolution of glass follows the order: boroaluminosilicate glass > vitreous reedmergnerite > vitreous albite > silica glass, which is the same order of increasingly negative 29Si chemical shifts. The chemical shift of 29Si is a measure of the extent of bond overlap between Si and O and correlates with the forward rate of reaction. Thus, dissolution appears to be rate-limited by rupture of the Si—O bond, which is consistent with the tenants of Transition State Theory (TST). Therefore, dissolution at far from equilibrium conditions is dependent upon the speed of the rate-controlling elementary reaction and not on the sum of the free energies of hydration of the constituents of boroaluminosilicate glass.« less

Authors:
 [1];  [1];  [1];  [1];  [2];  [3];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Nevada, Las Vegas, NV (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
939012
Report Number(s):
PNNL-SA-56660
Journal ID: ISSN 0016-7037; GCACAK; 14592; DF0961000; TRN: US0806077
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 72; Journal Issue: 12; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ABSORPTION SPECTROSCOPY; BOROSILICATE GLASS; CHEMICAL SHIFT; CHEMISTRY; DISSOLUTION; FELDSPARS; FLOW RATE; FREE ENERGY; GLASS; HYDRATION; HYDROLYSIS; KINETICS; POLYMERIZATION; RADIOACTIVE WASTE DISPOSAL; RUPTURES; SATURATION; SILICA; SURFACE AREA; VELOCITY; borosilicate glass; dissolution kinetics; Free Energy of Hydration model; Si-29 NMR spectroscopy; experimental; Environmental Molecular Sciences Laboratory

Citation Formats

Icenhower, Jonathan P., McGrail, B. Peter, Shaw, Wendy J., Pierce, Eric M., Nachimuthu, Ponnusamy, Shuh, David K., Rodriguez, Elsa A., and Steele, Jackie L.. Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory. United States: N. p., 2008. Web. doi:10.1016/j.gca.2008.02.026.
Icenhower, Jonathan P., McGrail, B. Peter, Shaw, Wendy J., Pierce, Eric M., Nachimuthu, Ponnusamy, Shuh, David K., Rodriguez, Elsa A., & Steele, Jackie L.. Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory. United States. https://doi.org/10.1016/j.gca.2008.02.026
Icenhower, Jonathan P., McGrail, B. Peter, Shaw, Wendy J., Pierce, Eric M., Nachimuthu, Ponnusamy, Shuh, David K., Rodriguez, Elsa A., and Steele, Jackie L.. Mon . "Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory". United States. https://doi.org/10.1016/j.gca.2008.02.026.
@article{osti_939012,
title = {Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory},
author = {Icenhower, Jonathan P. and McGrail, B. Peter and Shaw, Wendy J. and Pierce, Eric M. and Nachimuthu, Ponnusamy and Shuh, David K. and Rodriguez, Elsa A. and Steele, Jackie L.},
abstractNote = {Abstract—The dissolution kinetics of five chemically complex and two chemically simple borosilicate glass compositions (Na-B-Si±Al) were determined over a range of solution saturation values by varying the flow-through rates (1 to 100 mL d-1) in a dynamic single-pass flow-through (SPFT) apparatus. The chemically complex borosilicate glasses are representative of prospective hosts for radioactive waste disposal and are characterized by relatively high molar Si/(Si+Al) and Na/(Al+B) ratios (>0.7 and >1.0, respectively). Analysis by x-ray absorption spectroscopy (XAS) indicates that the fraction of ivB to iiiB (N4) varies from 0.66 to 0.70. Despite large differences in bulk chemistry, values of δ 29Si peak shift determined by MAS-NMR varies only by about 7 ppm (δ29Si = -94 to -87 ppm), indicating small differences in polymerization state for the glasses. Forward rates of reaction measured in dynamic experiments converge (average log10 rate [40°C, pH 9] = -1.87±0.79 [g/(m2•d)]) at high values of flow-rate (q) to sample surface area (S). Dissolution rates are independent of total Free Energy of Hydration (FEH) and this model appears to overestimate the impact of excess Na on chemical durability. For borosilicate glass compositions in which molar Na > Al + B, further addition of Na appears to stabilize the glass structure with respect to hydrolysis and dissolution. Compared to other borosilicate and aluminosilicate glasses, the glass specimens from this study dissolve at nearly the same rate (0 to ~55×) as the more polymerized glasses, such as vitreous reedmergnerite (NaBSi3O8), albite, and silica. Dissolution of glass follows the order: boroaluminosilicate glass > vitreous reedmergnerite > vitreous albite > silica glass, which is the same order of increasingly negative 29Si chemical shifts. The chemical shift of 29Si is a measure of the extent of bond overlap between Si and O and correlates with the forward rate of reaction. Thus, dissolution appears to be rate-limited by rupture of the Si—O bond, which is consistent with the tenants of Transition State Theory (TST). Therefore, dissolution at far from equilibrium conditions is dependent upon the speed of the rate-controlling elementary reaction and not on the sum of the free energies of hydration of the constituents of boroaluminosilicate glass.},
doi = {10.1016/j.gca.2008.02.026},
url = {https://www.osti.gov/biblio/939012}, journal = {Geochimica et Cosmochimica Acta},
issn = {0016-7037},
number = 12,
volume = 72,
place = {United States},
year = {2008},
month = {4}
}