Precipitation of Calcium Carbonate on a Steel Cathode

Abstract

The precipitation of calcium carbonate from water containing 3 mM CaCO3 has been studied on a rotating disk electrode made of 304 stainless steel. When the electrode is polarized at potentials where hydrogen is produced or dissolved oxygen is reduced, the reduction reaction raises the interfacial pH sufficiently to precipitate the carbonate. The effects of current density and modulation on the precipitation process have been examined. This paper reports on the nature of the precipitates formed. Depending on the experimental conditions, one may obtain calcite, vaterite or aragonite. A mathematical model has been developed to describe the transport phenomena in the boundary layer on the rotating disk electrode. This model takes into account convection, diffusion, and migration as well as the homogeneous ionic equilibria in order to estimate the degree of supersaturation at the surface.