Much of the challenge in understanding geochemical processes at fluid-solid interfaces is the complexity and small scale of these important regions.  That is, at a fluid-solid interface, a diverse range of interactions of dissolved species and solvent molecules meet potentially dozens of reactive sites on solid surfaces to create a rich and complex reactive environment.  Dave Wesolowski ran a decade-long project on understanding nanoscale complexity at mineral-water interfaces, informally known as the electric double layer project.  In this project, they combined multiple experimental and computational tools to understand ion and solvent molecule sorption and transport in the interfacial region.  Their pioneering work led to transformative advances in how we think of, measure and simulate, mineral-water interfaces.<br/><br/>Here, our recent results are shown on how we are using similar concepts and techniques to understand mineral precipitation on planar substrates, but how these diverse reactions play out in porous media.  We start at the atomic-level probing interface structure and sorption of ions on planar surfaces. We then show how sorption of the electrolyte and incorporation of impurities can affect crystal growth, both on single crystals, but also the nucleation and growth of precipitates in an idealized porous medium, a glass bead pack.  The system that we will focus on is barite (BaSO4)-water interface, with impurities including the background electrolyte and strontium.  We find that the “background electrolyte” concept is a misnomer and that these dissolved species are playing an active role in determining the rate of reactions.  Similarly, the relationship between the effect of the strontium impurity on growth morphology and its affect on the rates of precipitation, having different effects on nucleation and growth of barite.

Atomic- to pore-scale geochemistry: Effects of ion sorption and incorporation on mineral growth

255th National Meeting (2018)

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