Ph.D. topics

Heterogeneous sorption of f-elements on nanotopographic mineral surfaces

Ph.D. student

Siglinde Holzknecht

Supervisor

Prof. Dr. Cornelius Fischer(HZDR)

Department

Reactive Transport

Period

09/2024-08/2027

Description

In deep geological repositories for nuclear waste, the surrounding rock formation (host rock) serves as a critical barrier against radionuclide migration into the biosphere. Multiple potential host rocks contain phyllosilicates, which have shown high efficiency in radionuclide sorption.

This project focuses on investigating the sorption of trivalent f-elements on phyllosilicates, both as pure minerals and as rock components. An important factor in sorption efficiency is the nanotopographic architecture of the crystal surface. Previous numerical work has shown a variability of about an order of magnitude in sorption efficiency as a function of the type and availability of reactive sites on the crystal surface.1 Dissolution experiments are conducted to mimic the nano- and microtopographic results of processes that occur in natural settings. We also plan to develop a routine for quantitative analysis of sorption reactions on sheet silicates using positron emission tomography. Overall, a combination of microscopic, spectroscopic and radio analytical methods are used in this project to elucidate reactive transport processes and thus take a major step towards a safe nuclear repository.

The work is part of the joint project “SPIEG3L” (Spatially resolved spectroscopies for the identification of interfacial processes and species of trivalent lanthanides and actinides), and funded by the German Federal Ministry of Education and Research.

Reference

1. Schabernack, J.; Oliveira, A. F.; Heine, T.; Fischer, C., Variability of Radionuclide Sorption Efficiency on Muscovite Cleavage Planes. Advanced Theory and Simulations (2023), 2300406.