Contact

Porträt Dr. Müller, Katharina; FWOG

Photo: André Wirsig

Dr. Katharina Müller

Head Surface Processes
k.muellerAthzdr.de
Phone: +49 351 260 2439

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Department of Surface Processes

The why? The how? The what?

The ultimate goal of our research, driven by scientific curiosity, is to gain fundamental and independent knowledge of the (geo)chemistry and environmental fate of long-lived radionuclides (RNs). One prominent and socially important application is the safe disposal of radioactive waste, to aid future generations in the responsibility of dealing with “our” legacy from energy production in nuclear reactors.

For this purpose we provide the radiochemical knowledge, namely structural and mechanistic data of important mobilizing and immobilizing reactions of RNs in solution, at interfaces, and in solids.

Our particular focus is using a variety of established and advanced microscopic and spectroscopic techniques, to accurately describe complex formation reactions and complex structures that govern RN interactions in the geosphere. In addition, we investigate the creation and chemical speciation of activation products in materials from nuclear power plants in the context of their safe decommissioning.

As part of a value chain, the derived structural information forms a sound basis for a reliable thermodynamic description of the investigated systems, which can be integrated in thermodynamic databases. The thermodynamic work is done in close collaboration with the department of Actinide thermodynamics.

Foto: Forschungsfelder der Abteilung Grenzflächenprozesse ©Copyright: Dr. Katharina Müller

Our core competencies

  • Chemistry of long-lived RNs – Expertise in handling RNs, ranging from fission- and activation products to transuranium elements, and access to radiation safety labs.
  • Structural characterization – Expertise in applying and coupling spectroscopic and microscopic as well as diffraction techniques for accessing molecular information.
  • Thermodynamic description of RN complexes – Using macroscopic, spectroscopic, and calorimetric information of reactant-water-surface phenomena as basis for the derivation of surface complexation models and their thermodynamic parameters.

Research fields

  • Coordination chemistry of RNs in aqueous solution and in human artificial biofluids.
  • Molecular characterization of RN reactions at natural and engineered mineral-water interfaces, e.g. REDOX and RULET project.
  • Environmental technetium chemistry., e.g. Young Investigator Group TecRad.
  • Experimental support for calculations of neutron fields and the resulting activities close to nuclear reactors, e.g. EBENE project.

Latest Publication

XAFS and DFT insights into the kinetics and mechanisms of technetium reduction by nanoparticulate magnetite

Zimmermann, T.; Mayordomo, N.; Oliveira, A. F.; Brandt, F.; Klinkenberg, M.; Barthel, J.; Schild, D.; Hockmann, K.; Stumpf, T.; Scheinost, A.

Abstract

Radioactive technetium-99 (⁹⁹Tc) is present in nuclear and medical waste. Its immobilization by magnetite (Fe(II)Fe(III)₂O₄) has been studied in the last decades, showing that magnetite reduces pertechnetate (Tc(VII)O₄⁻) to Tc(IV), which is either incorporated into the magnetite structure or forms Tc(IV)-Tc(IV)-dimers. The distribution between both phases as well as the incorporation mechanism remain, unclear. This work investigates the molecular environment of Tc after putting it in contact with presynthesized nanoparticulate magnetite as a function of pH (2 - 13) and time (up to 7 weeks). X-ray absorption spectroscopy (XAS) was combined with density functional theory methods (DFT) to decipher the mechanism of Tc(IV) incorporation. We observed that sorption of Tc(IV)-Tc(IV)-dimers initially occurs at pH 5 and pH 7, while Tc(IV) incorporation in magnetite prevails at longer times and at pH 10. We suggest that Tc(IV)-Tc(IV)-dimer sorption on magnetite is due to maghemitization, whereas Tc(IV) incorporation is due to the electron transfer from sorbed Fe2+ through magnetite and subsequent release of Fe(II) in solution (redox conveyor belt model), “burying” Tc(IV) into the magnetite structure. DFT calculations indicate that Tc(IV) incorporates in magnetite by an exchange of two Fe(II) atoms for one Tc(IV), keeping the charge balanced by creating a vacancy.

Keywords: Tc; Incorporation; Fe3O4; DFT; XAS

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-42933


More publications

A list of publications can be found here.

Research groups

Currently running third-party funded projects

  • Experimentally supported calculations of neutron fields and the resulting activities in spaces far from the reactor (EBENE) started: 04/2024, BMBF
  • Interactions of technetium with microorganisms, metabolites and at the mineral-water interface – Radioecological considerations (TecRad) started: 07/2022, BMBF
  • Redox reactivity of selenium in environmental geomedia (REDOX) started: 06/2022, ANDRA
  • Retention and solubility of dose-relevant radionuclides under the reducing near-field conditions of a repository in clay or crystalline rock (RULET) started 11/2024, BMUV

An overview of finished projects can be found here.

Team

Foto: Surface processes department

"Surface processes" department

Surface Processes

Head

NameBld./Office+49 351 260Email
Dr. Katharina Müller801/P2482439
k.muellerAthzdr.de

Employees

NameBld./Office+49 351 260Email
Dr. Astrid Barkleit801/P2073136
2512
2518
a.barkleitAthzdr.de
Aline Chlupka801/P2033198
2518
2523
a.chlupkaAthzdr.de
Dr. Norbert Jordan801/P2182148
n.jordanAthzdr.de
Dr. Mario Löw801/P3523154
m.loewAthzdr.de
Zarina Salkenova801/P2543487
z.salkenovaAthzdr.de
Stephan Weiß801/P3162758
2523
s.weissAthzdr.de
Maud Emilie Zilbermann801/P2543487
m.zilbermannAthzdr.de

"TecRad" Wechselwirkung von Technetium mit Mikroorganismen, Metaboliten und an Mineral-Wasser-Grenzflächen - Radioökologische Betrachtungen

NameBld./Office+49 351 260Email
Dr. Natalia Mayordomo Herranz801/P2522076
n.mayordomo-herranzAthzdr.de
Caroline Börner801/P2542251
c.boernerAthzdr.de
Irene Cardaio801/P2542251
i.cardaioAthzdr.de
Dr. Marcos Felipe Martinez Moreno3154
m.martinez-morenoAthzdr.de
Vijay Kumar Saini801/P3523328
v.sainiAthzdr.de

Alumni

Name at HZDR
Heidrun Neubert Lab assistant
Sara E. Gilson PostDoc
Christa Müller Lab assistant
Quirina Isabella Roode-Gutzmer Ph.D. student
Isabelle Jessat Ph.D. student,
gratuated 2023
Maximilian Demnitz Ph.D. student,
graduated 2022
Diana Marcela Rodriguez Hernandez Ph.D. student,
graduated 2021
Henry Lösch Ph.D. student,
graduated 2021
Manuel Eibl Ph.D. student,
graduated 2020
Susanne Lehmann Ph.D. student,
graduated 2020