The aim of this work was to determine the solubility of radionuclides in solutions of cellulose degradation products (CDP) and isosaccharinic acid (ISA) the main product of cellulose degradation. Thorium was the main radionuclide investigated as the solubility of tetravalent actinides in the near field of a nuclear waste repository at high pH and low Eh has been shown to increase in the presence of such ligands. The measurement of thorium solubility was achieved by using different methods e.g. liquid scintillation counting, gamma spectrometry, ICP-MS and ICP-OES. ICP-OES was shown to be the most accurate method for this analysis. Various methods have been used to obtain solubility values e.g. undersaturation and oversaturation, and these have been investigated to determine whether the values obtained from these methods differ. Solubility studies were carried out at different pHs (6, 8 and 12). The kinetics of the complexation of thorium with ISA and with CDP were investigated at these pHs. The concentration of ISA in a solution of synthesised 10% CDP was approximately 0.01 mol dm⁻³ . In high pH solutions, the solubility of thorium was found to be 31 times greater in a solution of CDP compared to a solution of ISA at the same ISA concentration. No significant differences in thorium solubilities were found in similar solutions at pH 6 and 8. The solubilities of cobalt, nickel and cadmium were measured in the presence of 10% CDP and an equivalent concentration of ISA. The solubilities of all the metals studied in a CDP solution increased when compared to solubilities in ISA. These findings suggest that there are other complexing ligands present in the CDP other than ISA. The CDP mixture was investigated by LC-ICP-MS to determine what other complexing agents were increasing the metal's solubility.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:504046 |
| Date | January 2008 |
| Creators | Heath, Charlotte Rebecca |
| Publisher | Loughborough University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://dspace.lboro.ac.uk/2134/11676 |
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