PNNL

Abstract

Based upon the framework of the terrace-ledge-kink model of dissolution [1], the site-specific dissolution kinetics at the CaCO3(1014) surface-water interface have been investigated for the first time using atomic force microscopy. The experiment was carried out in a solution cell where the "real time" dissolution kinetics were examined in an aqueous environment under different flow and temperature conditions. Results show that dissolution proceeds via the retreat of steps and the creation of pits on the surface. In the surface-reaction-controlled regime, retreat of single-layer steps was found to be anisotropic with two different velocities. By measuring the sum of the two velocities at different kink sites were obtained. The results suggest the although the surface morphology is predominated by the deep pits after the initial dissolution stage, the overall dissolution rate is controlled by the retreat of single-layer steps on the surface. The study provides not only valuable information on the relationship between the atomic structure and the site-specific reactivity of the surface, but also quantitatively deomonstrates the morphological variation of the CaCO3(1014) surface resulting form dissolution.