FWO-Institutskolloquium: „Electrostatic interactions at clay mineral surfaces: At the crossroads between mineralogy, geochemistry, and geophysics“

Datum

24.01.2024

Zeit

14:00 - 15:30

Sprecher

Christophe Tournassat

Zugehörigkeit

Professor at the University of Orléans, France

Sprache

en

Hauptthema

Chemie

Host

PD Dr. C. Fischer (FWOT)

Beschreibung

Electrostatic interactions at clay mineral surfaces: At the crossroads between mineralogy, geochemistry, and geophysics Christophe Tournassat (ISTO, University of Orléans, France; EESA, Lawrence Berkeley National Laboratory, USA) Clayey materials properties are key elements in several important subsurface energy-related applications, including the long-term disposal of nuclear wastes in geological repositories and the storage of CO2 in subsurface geological formations. Clayey materials show a remarkable array of desirable macro-scale properties such as very low permeability, strong adsorption, semi-permeable membrane properties, and high swelling pressure, which lead to slow advective transport rates, contaminant retardation, limited diffusion for anions, and self-sealing of fractures. These properties arise from the interactions of charged mineral surfaces with water and solutes present in the nanopores of these materials, among which electrostatic interactions often play a dominant role. The study of interactions between water molecules, ions, and individual clay mineral surfaces remains an intense field of research, providing a basic understanding to build predictive models for the simulation of clayey material behavior as a function of physical and chemical forcing. However, the behavior of nanoporous clay environments is complicated by the fact that the pore structure of clay materials, but also the surfaces and compositions of clay minerals, are heterogeneous, and that water and ions can be present in bulk water, incorporated within interlayer spaces, adsorbed to external surfaces, whether at basal or edge surfaces, or located within the electrical double layer. Mutual interactions between these system components lead to highly coupled processes and these couplings manifest themselves in macroscopic observations up to geological formation scale, such as geologic ultrafiltration, i.e. the accumulation of solutes on the inflow side of clay-rich lithologies. To understand and predict the coupling phenomena, a preferred approach is usually built on the following sequence: i) to examine the physical processes at the molecular and pore scale, ii) to up-scale the physical laws toward the continuum scale, and iii) to compare continuum scale model predictions to geophysical and geochemical observables. My talk will address some of the challenges related to this type of upscaling strategy focusing on the role of electrostatic interactions on clay minerals properties.

Letztmalig verändert: 24.01.2024, 07:40:05