Modelling calcite dissolution in a rotating disc reaction vessel

Abstract

The carbonate system is ubiquitous in nature, playing a role in many natural and industrial processes. For calcite dissolution, the kinetics and mass transport of the dissolved species reflect both the chemistry of the bulk, and the conditions at the dissolving interface. We formulate the dissolution problem as a set of coupled convection- reaction-diffusion equations that is not only consistent with the bulk chemistry, but is also connected with a Stefan condition for dissolution interface, treating it as a free boundary. The substantial difference in the order of magnitude of the various reaction rates decouples the system. The relatively slow speed of the moving interface allows for a quasi-steady solution. The model reproduces the experimentally observed behaviour without the need to introduce additional reactions occurring at the reacting surface.