Reactions at the mineral – water interface play a central role in environmental processes. Most studies are focused on probing ideally flat surfaces in the presence of bulk solution to emphasize the intrinsic reactivity of these systems. In natural environments, chemical reactions may occur in interconnected pore space, where the mineral-water interactions are controlled by advective-diffusive transport under fluid saturated conditions. Effect of fluid flow on reactive transport is a well-known phenomenon. However, reactivity of minerals under advection dominated conditions is not well studied. Here we present the effects of fluid flow on chemical and structural changes at the calcite (104) surfaces as a function of reaction progress using a novel microfluidic channel apparatus. A series of experiments were conducted using a microfluidic cell attached directly to the calcite (104) surface to assess surface reactivity under dynamic flow conditions. These confined microfluidic environments enable us to precisely control initial fluid composition and fluid velocity within the microfluidic channels. The mineral samples were reacted at room temperature with a dilute Pb2+ solution under far-from equilibrium conditions over a range of ionic strength. Reacted samples were analysed ex-situ using SEM, AFM, DHM, nano-SIMS, profilometry, synchrotron beam x-ray fluorescence and reflectivity. We observed emerging behaviour in calcite dissolution pattern and secondary PbCO3 deposition. We also observed that variations in flow rate and ionic strength affect the substrate dissolution rate and the distribution and morphology of secondary Pb-bearing precipitates within the flow channels. Understanding these effects will enable us to develop a predictive understanding of emergent phenomena in geochemical reactive transport processes involving metal-carbonates.

Heterogeneities at confined calcite-water interface driven by advective reactive transport

ACS Spring 2022

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