PNNL

Abstract

Scanning force microscopy (SFM) provides relatively unique opportunities for the detailed study of dissolution and growth processes real time in aqueous and other solutions. By providing a detailed image of the crystallographic features as they grow or dissolve, SFM helps provide a bridge between the atomic level site-specific reactions from solution and macroscopically observable surface morphology, reaction rates and solution composition. Over the past several years we have examined the effects of solution and flow conditions on the dissolution of calcite. The anisotropic structure of steps on the calcite cleavage surface produces a delightful interplay between the movement of steps and the surface morphology. The initial work focused on the movement of steps during dissolution in "pure" aqueous solution. This work has been followed by examination of the influence of various solution additions on the calcite dissolution and eventually the growth of a second crystal phase that appears to have an epitaxial relation to the calcite. The influence of the impurities on general calcite dissolution has been understood in terms of a "blocking" version of the terrace ledge kink (TLK) model of surface and surface reactions