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The use of electromigration as a qualitative technique to study the migration behaviour and speciation of uranium in the Boom Clay
-
N. Maes
Veröffentlicht/Copyright:
25. September 2009
Summary
Under the geochemical conditions prevailing in situ in the Boom Clay Formation (pH, Eh, …), calculations predict that U(OH)4 is the dominant uranium species present in the interstitial water and the concentration is solubility limited. However the boundary of the domain where the non solubility limited UO2(CO3)34− species dominates is very close. It is therefore of prime interest to know the correct speciation of uranium during the migration process.
Electromigration was used as technique with the advantage that it can provide information on the speciation because the movement of the species towards the electrodes depends on its charge and speciation. Electromigration experiments have been performed with preconditioned 233UO2(CO3)34− sources, starting from the hypothesis that this species should migrate without retardation towards the anode. Despite relatively long electromigration times, sufficient to displace strong retarded tracers, no displacement of the migration profile towards the anode was observed. All 233U remained near the source position, but the electropherograms clearly showed the presence of species moving towards the cathode. This indicates the presence of neutral or positively charged uranium species. These electropherograms are interpreted as a change in uranium valence state: reduction of UO2(CO3)34− and precipitation of U(IV) oxy-hydroxides near the source position. The solubility limited species, U(OH)4(aq), are carried with the pore water towards the cathode. The electromigration experiments indicate, in support of the speciation calculations, that the dominant migrating U-species is probably the solubility limited U(OH)4.
Received: 2001-9-7
Accepted: 2002-4-11
Published Online: 2009-9-25
Published in Print: 2002-9-1
© Oldenbourg Wissenschaftsverlag, München
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Artikel in diesem Heft
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- Complex formation of Eu(III) with humic acid and polyacrylic acid
- XAS study of technetium(IV) polymer formation in mixed sulphate/chloride media
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- The effects of alpha-radiolysis on UO2 dissolution determined from electrochemical experiments with 238Pu-doped UO2
- Radiolytic formation of Tc(IV) oxide colloids
- Radiation-chemical effects in the near-field of a final disposal site: role of bromine on the radiolytic processes in NaCl-solutions
- The reduction of U(VI) on corroded iron under anoxic conditions
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