Technetium-99 represents 6.1% of the fission product yield of U-235. It exists in nature in two main oxidation states; Tc(VII) species are mobile in the environment and the less mobile Tc(IV) species occur in reducing environments, such as soils or underground repositories. Tc(IV) has a solubility of approximately 10<sup>-7</sup> M in water, but the addition of complexing ligands increases Tc solubility and environmental mobility. It is important to investigate the interactions of Tc(IV) with environmentally relevant ligands. The stability constants of Tc(IV) complexes with several ligands that can be found in the soil (citrate, acetate, oxalate, EDTA and several other polyamino-polycarboxylates) have been quantified. Smaller and weaker complexing monodentate ligands, such as the halides, are also expected to be present in ground waters surrounding waste repository sites. These ligands can also play a role in increasing the solubility of Tc(IV) as previously seen with larger ligands, but no data is currently available on halide complex stability constants with Tc(IV). This study focuses on Tc(IV) complexation with halide ligands. The stability constants for the Tc(IV)-halide complexes were determined using a solvent extraction method.<br/>

Complexation of technetium(IV) with selected halides

255th National Meeting (2018)

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