Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524676
Title: Dissolution of a simulated magnox waste glass in aqueous solutions at temperatures below 100 degrees C
Author: Abraitis, Paul K.
Awarding Body: The University of Manchester
Current Institution: University of Manchester
Date of Award: 1999
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Abstract:
The dissolution of a complex, simulated Magnox Waste (MW) glass has been investigated in batch and flow-through experiments at temperatures below 100 °C. The experiments were designed to investigate the dissolution rate dependence on the solution pH and temperature, and to examine the rate influencing effects of aqueous Si and Al species. At ambient laboratory temperatures, enhanced release of B (relative to Si) is observed in acidic buffer media in the pH range 2.1 ≤ pH ≤ 6.8. Normalised release rates of B and Si are similar in basic media in the pH range 7.8 ≤ pH ≤ 9.9. Congruent dissolution of the glass in basic media is surface reaction-controlled and accompanied by the development of secondary gels containing Si, Al, Mg, Fe and a range of additional glass components including d- and f-block elements. Gel development has been identified in both batch and flow-through experiments where significant quantities of glass-derived solutes accumulate in the leachate. Extensive dissolution of the glass at pH 2 (60 °C) is accompanied by the development of Si-rich leached layers at the glass surface and dissolution continues in solutions supersaturated with respect to amorphous silica. Examination of the acid leached glass revealed that regions of the glass which are relatively Si-rich are more durable than those regions which are enriched in metallic glass components. The kinetics of MW glass dissolution were investigated in single-pass flow-through experiments. These experiments were designed to investigate the effects of dissolved Al and Si on the rate of dissolution at fixed pH and temperature (pH 9 and 40 °C). The rate reducing effects of dissolved Al are far greater than those of dissolved Si on a mole per mole basis. In Si-rich alkaline solutions, the concentration of Al is controlled to very low levels by the development of secondary gels. In the absence of significant quantities of dissolved Al, and in systems where Al is extensively complexed by ethylenediamine tetra-acetic acid (EDTA), rates of glass dissolution decrease with increasing silicic acid activity. These data are compared with predictions based on a number of rate law formulations
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.524676  DOI: Not available
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