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Providing the last piece of the puzzle

We already have a deep understanding of how iron behaves in the octahedral sheets of clay minerals. This research has added to our knowledge of the behaviour of tetrahedral sheets.

Project leader

Dr Anke Neumann

Eawag, Switzerland (Project Lead)



Project staff

Fabien Baron, University of Poitiers


Eawag discretionary funds


ETH Zürich, Switzerland

University of Poitiers, France

Pacific Northwest National Lab (PNNL), USA


Eawag initiated research on characterising the redox properties of clay minerals. We now have a much deeper understanding of processes in subsurface environments, including:

  • nutrient cycling
  • trace element mobility
  • organic pollutant transformation

This understanding has led to practical applications. For example, it has provided expert advice in assessing host rocks and buffer materials for radioactive waste storage. Clay minerals have a unique ability to buffer redox reactions over a large range of environmental conditions. This may originate from reversible changes in the redox state of iron in the octahedral sheet. Yet the role of iron in the tetrahedral sheets remained elusive.

Synthetic clay minerals with well-defined iron coordination have recently become available. We are investigating their redox properties. We are using a combination of electrochemical and spectroscopic methods. This research will complete our understanding of the redox buffering by iron-containing minerals in soils and groundwaters.