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[Dissolution experiments in anoxic condition]
[Dissolution experiments in oxic condition]

Dissolution mechanisms of Fe(hydr)oxides

Catalytic effects of redox reaction on ligand controlled dissolution

Dissolution of Fe(hydr)oxides is a key process in the iron cycle and is relevant, e.g., in coupled trace element cycles and in biological Fe acquisition. Despite the abundance of iron in many natural systems, its bioavailability is highly restricted due to the low solubility of Fe(hydr)oxides in environments with a circumneutral pH. To cope with the conditions of low biological Fe availability, organisms may exude organic compounds to increase its solubility by reductive and ligand controlled dissolution mechanisms.

Recently, we have shown synergistic effects between reductive dissolution and ligand-controlled dissolution in single goethite suspensions and in suspensions containing calcareous soil as well. However, the mechanism of redox promoted ligand-controlled Fe(hydr)oxide dissolution has not been studied intensively.

In our project, we hypothesize that electron transfer to structural Fe(III) by redox reaction labilizes the iron(hydr)oxide structure, and that this can accelerate ligand-controlled dissolution. To test this hypothesis we perform batch type dissolution experiments in the presence of reductant and ligand under the oxic and anoxic conditions at circumneutral pH values. We also perform dissolution experiments with organic compounds which play dual roles as reductant and ligand.

Since Fe is an essential nutrient for most organisms and contributes to the mobility of other trace metal in groundwater, understanding the mechanisms of dissolution of Fe(hydr)oxide is of great importance in geochemistry and biogeochemistry.

 

Researchers involved:

Ma. Kyounglim Kang, Department of Environmental Geosciences, University of Vienna

Dr. Walter D. Schenkeveld, Department of Environmental Geosciences, University of Vienna

Univ. Prof. Dr. Stephan M. Kraemer, Department of Environmental Geosciences, University of Vienna

Collaborators:

Prof. Dr. Janet G. Hering, Department Water Resources & Drinking Water, Swiss Federal Institute of quatic Science & Technology (Eawag)

Dr. Stephan J. Hug, Department Water Resources & Drinking Water, Swiss Federal Institute of Aquatic Science & Technology (Eawag)

Dr. Susan C. Borowski, Department Water Resources & Drinking Water, Swiss Federal Institute of Aquatic Science & Technology (Eawag)

Dr. James D. Kubicki, Department of Geological Sciences, University of Texas

M.Sc. Jagannath Biswakarma, Department Water Resources & Drinking Water, Swiss Federal Institute of Aquatic Science & Technology (Eawag)

 

 

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