ENVR 116 |
| To quantify the rate of glass dissolution, a series of experiments have been conducted using the single-pass flow-through (SPFT) apparatus. The SPFT apparatus allows for the transfer of fresh input solution from a reservoir bottle into a Teflon reactor and finally into a sample collection vial. These experiments were conducted under varying conditions such as: temperatures ranging from 23 to 90°C, solution pH, from 7 to 12 all calculated by the thermodynamic software package EQ3NR. Results from these experiments show that as the temperature and solution pH increases the glass dissolution rate also increases. For example, the dissolution rate at 90°C was approximately 56 times higher at pH (23°C) 12.0, 5.66±1.08 g m-2 d-1, compared to pH (23°C) 7.0, 0.016±0.003 g m-2 d-1. Performing linear regression as a function of pH at each temperature resulted in a slope, power law coefficient, of 0.50±0.05 indicating that this value does not depend on temperature within experimental error. Temperature also affects the dissolution rate, evident by as much as a 14x increase in the rate with a 30° increase in temperature. Applying an Arrhenius expression to the data obtained at each pH suggested that the dominant mechanism of dissolution was a surface-controlled process, evident by an activation energy (Ea) of 58±4 kJ mol-1. Although translation and interpretation of these SPFT results to long-term glass dissolution under repository conditions requires further analysis, these results provide the rate-law parameters needed to conduct source-term release calculations using reactive transport models. |
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General Papers
6:00 PM-8:00 PM, Wednesday, August 22, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Environmental Chemistry |