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Mobility of radionuclides enhanced by complexing agents used in a repository: Modeling sorption and transport
Karimzadeh, L.; Lippold, H.; Fischer, C.ORC
Among the organic inventory of a nuclear waste repository, aminopolycarboxylic acids, which are used as decontamination agents during operation, are of particular concern in view of their chelating capability and high persistence, but data regarding their impact on the mobility of radionuclides in geological barriers are missing so far. Migration in the host rock is controlled by sorption reactions on mineral surfaces, potentially affected by organic complexing ligands. As a case study, using 152Eu as a short-lived tracer analogue of actinides, we investigated sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of the complexant diethylenetriaminepentaacetic acid (DTPA). The transport behavior was studied in column experiments (up- and down-flooding) at neutral pH in order to detect possible inconsistencies between sorption in batch systems and retardation in dynamic systems.
The effect of DTPA on sorption of Eu(III) was found to be strongly dependent on pH. At neutral and alkaline conditions, sorption is considerably decreased, resulting in accelerated breakthrough and facilitated elution in column experiments. Sorption as a function of DTPA concentration and pH was completely described by surface complexation modeling based on the Diffuse Double Layer Model of Dzombak and Morel, using the speciation program PHREEQC coupled with the parameter estimation code PEST. Results of column experiments were simulated in 1D calculations by means of the obtained surface complexation parameters. Breakthrough and elution curves were perfectly reproduced without readjustments.
  • Poster
    Jahrestagung der GDCh, Fachgruppe Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29859
Publ.-Id: 29859