Verification of derived SCP and chosen bottom-up approach
Batch- and titration experiments of single mineral phases are conducted in order to derive so-called surface complexation parameters that consist of protolysis constants (derived from titration curves), and surface site densities as well as stability constants of surface complexes of the according element-mineral composition (obtained from batch-experiments).
To verify the determined surface-complexation parameters and to verify the chosen bottom-up approach a mixture of minerals (synthetic sediment) is applied as a further batch-experiment with a similar experimental set-up as illustrated here. The bottom-up approach leads to the simulation describing sorption behavior of a sediment by means of each constituent. The scope of this experiment is to model the sorption behavior of the synthetic sediment by applying the priorly assessed surface-complexation parameters. Modeled results should correlate well with the data resulting from batch-experiments that employ the synthetic sediment (verification of the chosen approach). The synthetic sediment is composed of 80% quartz and 10% muscovite, orthoclase, respectively, representing typical sediment of the Gorleben overburden.
Two solid/liquid ratios (M/V), three element-concentrations, and three pH-values ranging between 6 and 9 are applied:
- Mineral composition: 80% quartz, 10% muscovite, 10% orthoclase
- Solid/liquid ratio: 1/80 and 1/320 g ml-1
- Element: Eu3+
- Concentration of Eu3+: 10-5 mol L-1, 5∙10-6 and 10-6 mol L-1
- pH: 3 - 8
- Background solution: 0.01 mol L-1 NaClO4
Evaluation of Eu sorption on the synthetic sediment is still onging - results will be published the beginning of 2019.
Noseck, U., Brendler, V., Flügge, J., Stockmann, M., Britz, S., Lampe, M., Schikora, J., Schneider, A., 2012. Realistic integration of sorption processes in transport codes for long-term savety assessments. GRS-297, BMWi-FKZ 02E10518, Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig, 293 p.
Back to Batch Experiments