Porträt Prof. Dr. Brendler, Vinzenz; FWOA

Prof. Dr. Vinzenz Brendler

Head of Department
Thermo­dynamics of Actinides
Phone: +49 351 260 2430

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Actinide thermodynamics department

Image: FWOA department image ©Copyright: Prof. Dr. Vinzenz Brendler


The research topics of the Department of Actinide Thermodynamics within the Institute of Resource Ecology are clustered around the determination of thermodynamic (and kinetic) parameters, their evaluation, processing, storage in respective databases and utilization for geochemical modeling. From a chemical point of view the focus is set on heavy metal contaminants, namely long-lived radionuclides. Their environmental fate, including migration and entrance into the food chain is of paramount societal concern.  Respective precaution, detoxification, separation and remediation measures need to be designed on the basis of a mechanistic understanding of all relevant physico-chemical processes. Then in turn a realistic, i.e. precise and robust forecast of their dissemination in geo- and biosphere and the risk involved for human health becomes possible.

Whereas the thermodynamic of aquatic species is often quite well understood, the picture is different for surface processes such as surface complexation, ion exchange, mineral transformation and surface precipitation - all of them considered important retardation mechanisms in complex environmental systems. With respect to solid phases research primarily deals with those minerals dominati

ng most rocks and soils. Prominent examples are the rock-forming constituents of crystalline rocks such as quartz, feldspars and mica, or alumosilicates such as kaolinite, illite, or montmorillonite. Engineered systems of interest are iron minerals and cementitious compounds.

Based on own investigations but also strongly embedded in the research topics of other departments (namely Surface Processes, Chemistry of the f-Elements,  Molecular Structure and Biogeochemistry) the identification of (surface) species and development of molecular models lays the foundation of realistic sets of species and their reaction equations - usually called model development. In a second step formation constants and other thermodynamic parameters are determined through experimental series under varying boundary conditions like pH, redox potential, ionic strength, temperature or CO2 partial pressure. This allows for the parameterization of the models derived afore. Species sets, reactions and parameters then support the compilation of respective geochemical databases providing required for the assessment of the macroscopic migration behavior of the long-lived radionuclides. Respective codes are shared with the department of Reactive Transport, where the team also provides many aspects of surface characterizations needed for our own model development. Another overarching goal is a tiered approach towards upscaling from the nano- to the macro scale, bridging the distance between atomistic investigations and the large scale prognostics required e.g. in performance assessment of nuclear waste repositories and covering distances of several km over up to one million years.

The actual major research topics of our department can be su

mmarized as follows:

Latest publication

Natural and synthetic plagioclases: Surface charge characterization and sorption of trivalent lanthanides (Eu) and actinides (Am, Cm)

Lessing, J.; Neumann, J.; Lützenkirchen, J.; Bok, F.; Moisei-Rabung, S.; Schild, D.; Brendler, V.; Stumpf, T.; Schmidt, M.

The environmental fate of radiotoxic actinides is controlled by their interactions with feldspars. Here, the sorption of trivalent minor actinides (Am, Cm) and their rare earth analogue Eu onto synthetic pure Ca-feldspar (anorthite) and natural plagioclases of different Ca contents is investigated, covering ranges of [M3+] (52 nM–10 μM), solid-liquid ratios (1–3 g/L), pH (3–9), and ionic strengths (0.01–0.1 M NaCl) under both ambient and CO2-free conditions. The zeta potential shows an unusual increase and charge reversal between pH 4 and 7 with increasing amount of Ca and Al in the feldspar crystal lattice, which is likely connected to adsorption and/or surface precipitation of dissolved Al3+. Streaming potential measurements yield (de)protonation constants for anorthite surface sites of log K- = -6.94 ± 0.38 and log K+ = +6.84 ± 0.38. Batch sorption data shows strong immobilization of M3+ by plagioclases at mildly acidic and basic pH. Time-resolved laser fluorescence spectroscopy using Cm indicates the formation of an inner-sphere complex and its two hydrolyzed forms. The complex reactivity of dissolved Al3+ at the plagioclase-water interface severely complicated the development of a surface complexation model, emphasizing the need for additional research in this area.

Keywords: Ca-feldspar; Anorthite; Sorption; Trivalent metal ions; TRLFS; Surface Complexation Model; Charge Reversal



NameBld./Office+49 351 260Email
Prof. Dr. Vinzenz Brendler801/P2502430


NameBld./Office+49 351 260Email
Dr. Frank Bok801/P2023551
Rodrigo Castro
Viktor Dück801/P3063241
Alexandra Duckstein801/P1532774
Dr. Stephan Hilpmann801/P3062860
Dr. Jerome Kretzschmar801/P2073136
Dr. Elmar
Dr. Solveig Pospiech801/P2052011
Dr. Anke Richter801/P2022426
Dr. Katja Schmeide801/P2082436
Salim Shams Aldin Azzam801/P3482386
Claudia Sieber801/P2542251
Susanne Zechel801/P3523328



NameBld./Office+49 351 260Email
Dr. Harald Foerstendorf801/P2513664


NameBld./Office+49 351 260Email
Sabrina Beutner801/P2032429
Tim Gitzel801/P3162025
Dominik Goldbach801/P2033198
Karsten Heim801/P2012434
Sylvia Schöne801/P2033198