The dissolution of silicate materials such as minerals, glasses, and cement pastes in geologic media has been the subject of investigation for more than 50 years. However, our current understanding of heterogeneous molecular- to nano-scale processes driving fluid-silicate interactions remains insufficient to enable accurate predictions of macroscopic geochemical data related to the long-term carbon cycle, soil formation, nutrient cycling in the critical zone and durability of nuclear waste depositories. In all these areas, it is known that the formation of silica-rich nanoporous coatings at reacting interfaces constitutes a key confounding factor. The importance and attributes of these interfacial layers are yet largely overlooked.<br/><br/>Here, we have investigated the properties of the nanoporous interfacial layers using advanced analytical techniques and high-performance atomistic simulations. Direct measurement of the interfacial dissolution-reprecipitation reactions (using feldspars and ISG glass as model crystalline and amorphous silicate materials) was carried out at multiple scales using in situ and surface sensitive techniques, including synchrotron-based grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), transmission electron microscopy (TEM) and vertical scanning interferometry (VSI). The data revealed the existence of intricate relationships between the multi-scale porosity of such complex media and the associated local ionic mobility in the porous layers.<br/><br/>Based on these findings we investigated the mobility of water and alkali ions through relevant nanoporous systems using molecular dynamics (MD) modeling. Realistic water-silica-ions interactions were generated by including the effects of negative surface charge. Single cylindrical silica nanopores were evaluated in their ability of to sustain concentration gradients of ions by estimating their permeability and salt rejection capability. Our results support the analogy of such systems with semi-permeable membranes and nanofluidic diodes, and the results may ultimately explain the ability of nanoporous interfacial layers to modulate fluid-mineral interactions.

Control of the macroscopic dissolution rates of silicate materials by nanoporous interfacial layers

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.