468339 Electrostatic Origin of Enhanced Rate of Silica Surface Dissolution

Monday, November 14, 2016: 10:15 AM
Union Square 23 & 24 (Hilton San Francisco Union Square)
Kai Kristiansen, Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, Howard Dobbs, Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA, Markus Valtiner, Max-Planck-Institut f. Eisenforschung GmbH, Düsseldorf, Germany, George W. Greene, Institute for Frontier Materials, Deakin University, Victoria, NSW, Australia, J. Boles, Department of Earth Science, University of California at Santa Barbara, Santa Barbara, CA and Jacob Israelachvili, Department of Chemical Engineering, University of California at Santa Barbara, Santa Barbara, CA

Using an electrochemical cell in a Surface Forces Apparatus (EC-SFA) we found an enhanced dissolution rate of silica surfaces in close proximity to either muscovite mica or a gold surface as functions of time and electrochemical potential. The surfaces was pressed together at relatively low pressures (a few atm) while submerged in weak electrolyte solutions at 25°C and over a wide range of pH. Typical dissolution rates varies from 0.1 – 4 Å/ min, depending on the “effective” potential difference Δψ. For the silica-mica interface the origin of the Δψ is interpreted as arising from the overlapping of the double layers of the surfaces. The Δψ of the gold surface was controlled by a potentiostat. We find that changes in the dissolution rates of silica correlate quantitatively with the Δψ via a Butler-Volmer type equation, suggesting the dissolution is driven, at least in part, by electrochemical reactions. Our finding may have implications for a wide variety of applications, from geological processes to chemical mechanical polishing.

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See more of this Session: Fundamentals of Interfacial Phenomena I
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