Dissolution Kinetics of Solid Particles and the Role of Aggregation: Vaterite Dissolution

We report the dissolution kinetics and mechanism of dimeric and larger aggregates of quasi-spherical particles of spherulitic vaterite, CaCO3, showing that dissolution occurs under thermodynamic control for all species, as seen for the corresponding monomeric species. While the dissolution rate measured via the variation of the projected two-dimensional area with time is, within experimental error, identical for all species, the dissolution time scale required for complete dissolution increases proportionally with particle size. We conclude that the time scale of complete dissolution time scale reflects the extent of aggregation, the solubility of vaterite, and the diffusion coefficient of the dissolved species. Generic inferences on the role of aggregation on the dissolution kinetics of solid particles are drawn.