PD Dr. habil. Moritz Schmidt

Head Chemistry of the f-elements
Phone: +49 351 260 3156
+49 351 260 2536

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Structures and Reactivity at the Water/Mineral Interface

Retention mechanismsThe Helmholtz-funded Young Investigator Group "Structures and Reactivity at the Water/Mineral Interface"was a group funded by the Helmholtz Association from 2013 to 2018. The group worked on understanding the reactions of the actinides (particularly Pu, Am, and Cm) at mineral surfaces on the molecular level. The work is embedded in our institute's efforts to provide reliable information as a basis for the safety case of a potential nuclear waste repository, where the mobility of the actinides will depend on their retention by the surrounding mineral phases.

The ternary system consisiting of actinide, solution, and mineral surface may host a wide range of chemical reactions (see figure). The retention potential of these reactions will vary significantly, which is why a quantification without understanding of the underlying mechanisms of retention is insufficient. As an example, a structurally incorporated ion will only be remobilized, if the host mineral phase dissolves macroscopically, on the other hand "outer sphere" sorption complexes may become unstable by a mere change in ionic strength.

Accurate description of such a system requires the use of cutting edge techniques capable of acquiring molecular information selectively from the mineral surface. To this end, our group focuses on applying surface X-ray diffraction techniques (crystal truncation rods - CTR und resonant anomalous X-ray reflectivity - RAXR) as well as site-selective time-resolved laser-induced fluorescence spectroscopy (TRLFS). Both techniques allow us to determine the speciation of actinides at an interface in situ at environmentally relevant trace concentration levels. The techniques are complementary, in that TRLFS yields information on the local structure surrounding an adsorbate, while CTR and RAXR yield a full structural picture of the interface from bulk crystal to bulk solution. This fundamental research will help to make long-term, safe disposal of nuclear waste possible.

The group was positively evaluated and expired as scheduled on September, 30th 2018.

Group membersGruppenfoto_231116

  • Dr. Moritz Schmidt
  • Sophia Hellebrandt
  • Sebastian Reese
  • Dr. Canrong Qiu
  • Dr. Bin Xiao
  • Konrad Molodtsov
  • Julia Neumann
  • Dr. Erik V. Johnstone
  • Dr. Sascha Hofmann
  • Dr. Stefan Hellebrandt

Selected publications