Session: Molecular Processes at Mineral-Water Interfaces:

The study of the reactivity of carbonate rocks is essential to the development of novel and more efficient strategies for CO₂ storage or enhanced oil recovery among others. Since their reactivity towards other aqueous phases is controlled by nanoscale interfacial processes, probing the molecular interactions at the mineral-water interface is therefore needed to gain a better control over energy production and/or storage processes involving these materials.
Carbonate rocks are of special interest since they are formed in a large variety of environments. They present thus a complex structure, heterogeneous composition – potentially including some organic matter – and textures made of (bio)minerals, which results in a surface chemistry with an inherent heterogeneity down to the nanoscale. The scale of observation – from the mm to the nm – is therefore pertinent and potentially an important parameter when describing surface chemistry properties of this rocks.
Here, we present a study of the surface properties of carbonate rocks probed at the nanoscale using Atomic Force Microscopy (AFM), but exploring multiple spatial scales up to the mm. We have measured the topographical features of the carbonate rocks and identified various carbonate cements and 5 bioclasts, namely bryozoans, mollusks, echinoderms, red algae and foraminifera. We have determined in detail the main features of the microstructures for each type of bioclast and compared them with that of the cements. In addition to multi-scale imaging of bioclasts, we also present their adhesion properties in air and in aqueous environments. From these observations we have evaluated the spatial variability of surface chemistry properties across scales. Overall, this AFM study presents a detailed characterization of the carbonate biomineral nature in carbonate rocks and the role they play in the surface chemistry.

Alexander Van Driessche

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