Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 53: Solid-liquid interfaces: Reactions and electrochemisty III (joint session O/CPP)

CPP 53.2: Vortrag

Mittwoch, 14. März 2018, 15:15–15:30, MA 144

Real-Time Measurement of Silica Dissolution at the interface with water — •Jan Schaefer, Ellen H.G. Backus, and Mischa Bonn — Max Planck Institute for Polymer Research, Mainz, Germany

Dissolution processes of minerals in water are often studied on macroscopic scales by detecting dissolution products in bulk solution and inferring microscopic reaction rates using models that require assumptions. Here, we present a direct way to measure the dissolution rate of silica, a mineral of geological significance, in contact with water. We find that on a surprisingly short timescale of tens of hours, the interfacial concentration of dissolution products saturates at a level close to the solubility of silica (~ millimolar). As the bulk solution is known to be equilibrated only after several weeks, our results reveal that the macroscopic dissolution process is limited by diffusion. A comparison with a simple 1D reaction/diffusion model indicates that the diffusion coefficient of dissolved silica decays with progressing dissolution which suggests that the small silicic acid species polymerize next to the silica surface.