Retention of redox sensitive metals/metalloids at reducing mineral surfaces

Description: Redox reactions, in particular multi-electron transfer reactions, tend to be slow and, hence, redox couples in natural systems often do not reach equilibrium even over very long time-scales. Sorption and subsequent transfer of electrons in an inner- outersphere complex between the redox partners tends to drastically increase the reaction rate and hence provides an important path in the redox cycling of trace elements. Ferrous iron minerals play a particularly important role as they provide both reducing capacity through their structural Fe(II), which is a stronger reducing agent than aqueous Fe(II), and a mineral surface that can mediate the electron transfer. Hence, ferrous oxides, silicates, and sulphides tend to reduce redox sensitive trace elements from their higher oxidation states. Only very few studies have assessed the thermodynamics, reversibility and kinetics of coupled sorption and redox processes of trace elements at surfaces of ferrous minerals. This project, thus, aims at quantifying and comparing the attenuation of U(VI) (extent, rate, and reversibility) at surfaces of phlogopite/biotite; goethite/magnetite; and pyrite at given near-natural conditions, thereby improving conceptual understanding of reductive sorption processes and providing missing rate data. This project is a part of the EU Integrated Project Fundamental Processes Of Radionuclide Migration (FUNMIG).

Project leader: Maria Malmström
Funding: Integrated Project within EU