(86j) Electrostatic Origin of Enhanced Rate of Silica Surface Dissolution

Kristiansen, K., University of California Santa Barbara
Dobbs, H., University of California Santa Barbara
Valtiner, M., Max-Planck-Institut f. Eisenforschung GmbH
Greene, G. W., Deakin University
Boles, J., University of California at Santa Barbara
Israelachvili, J., University of California Santa Barbara
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 â?? 4 Ã?/ min, depending on the â??effectiveâ? potential difference Î?Ï?. For the silica-mica interface the origin of the Î?Ï? is interpreted as arising from the overlapping of the double layers of the surfaces. The Î?Ï? of the gold surface was controlled by a potentiostat. We find that changes in the dissolution rates of silica correlate quantitatively with the Î?Ï? 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.