TY - JOUR
T1 - Aluminoborosilicate waste glass dissolution under alkaline conditions at 40°C
T2 - Implications for a chemical affinity-based rate equation
AU - Pierce, E. M.
AU - Richards, E. L.
AU - Davis, A. M.
AU - Reed, L. R.
AU - Rodriguez, E. A.
PY - 2008
Y1 - 2008
N2 - Single-pass flow-through experiments were conducted with aluminoborosilicate waste glasses to evaluate how changes in solution composition affect the dissolution rate (r) at 40°C and pH (23°C) ≤ 9.0. The three prototypic low-activity waste (LAW) glasses, LAWE-1A, -95A and -290A, used in these experiments span a wide range covering the expected processing composition of candidate immobilised low-activity waste (ILAW) glasses. Results suggest incongruent release of Al, B, Na, and Si at low flow-rate (q) to sample surface area (S), in units of (m s?1), (log10(q/S) < ?8.9) whereas congruent release is observed at high q/S (log10(q/S) > ?7.9). Dissolution rates increase from log 10(q/S) ? ?9.3 to ?8.0 and then become constant at log 10(q/S) > ?7.9. Forward (maximum) dissolution rates, based on B release, are the same irrespective of glass composition, evident by the dissolution rates being within the experimental error of one another (r 1A ≤ 0.0301 ± 0.0153 g m?2 day?1, r95A ≤ 0.0248 ± 0.0125 g m?2 day?1, and r290A ≤ 0.0389 ± 0.0197 g m?2 day ?1). The results also illustrate that as the activity of SiO 2(aq) increases, the rate of glass dissolution decreases to a residual rate. The pseudo-equilibrium constant, Kg, (log 10(Kg) ≤ ?3.7) predicted with these results is slightly lower than the K for chalcedony (log10(K) ≤ ?3.48) at 40°C. Finally, these results support the use of a chemical affinity-based rate law to describe glass dissolution as a function of solution composition.
AB - Single-pass flow-through experiments were conducted with aluminoborosilicate waste glasses to evaluate how changes in solution composition affect the dissolution rate (r) at 40°C and pH (23°C) ≤ 9.0. The three prototypic low-activity waste (LAW) glasses, LAWE-1A, -95A and -290A, used in these experiments span a wide range covering the expected processing composition of candidate immobilised low-activity waste (ILAW) glasses. Results suggest incongruent release of Al, B, Na, and Si at low flow-rate (q) to sample surface area (S), in units of (m s?1), (log10(q/S) < ?8.9) whereas congruent release is observed at high q/S (log10(q/S) > ?7.9). Dissolution rates increase from log 10(q/S) ? ?9.3 to ?8.0 and then become constant at log 10(q/S) > ?7.9. Forward (maximum) dissolution rates, based on B release, are the same irrespective of glass composition, evident by the dissolution rates being within the experimental error of one another (r 1A ≤ 0.0301 ± 0.0153 g m?2 day?1, r95A ≤ 0.0248 ± 0.0125 g m?2 day?1, and r290A ≤ 0.0389 ± 0.0197 g m?2 day ?1). The results also illustrate that as the activity of SiO 2(aq) increases, the rate of glass dissolution decreases to a residual rate. The pseudo-equilibrium constant, Kg, (log 10(Kg) ≤ ?3.7) predicted with these results is slightly lower than the K for chalcedony (log10(K) ≤ ?3.48) at 40°C. Finally, these results support the use of a chemical affinity-based rate law to describe glass dissolution as a function of solution composition.
KW - Boron coordination
KW - Forward rate
KW - Free energy of hydration
KW - Low-activity waste glass
KW - Transition State Theory
UR - http://www.scopus.com/inward/record.url?scp=39749177903&partnerID=8YFLogxK
U2 - 10.1071/EN07058
DO - 10.1071/EN07058
M3 - Article
AN - SCOPUS:39749177903
SN - 1448-2517
VL - 5
SP - 73
EP - 85
JO - Environmental Chemistry
JF - Environmental Chemistry
IS - 1
ER -