Theory and Experiments for Dissolving Solids in Water

The dissolution of soluble particulate matter is a common process in the chemical industry. Poor understanding of the dissolution process may lead to unnecessarily high process times or poorly prepared feeds. A better understanding of this process would help alleviate these problems. This article reviews the previous literature findings on dissolution, and highlights the shortcomings, mostly due to the fact that average values of the relevant parameters have to be used and that the effects of both reducing particle size and reducing driving force are thus neglected. A model is therefore developed to analytically account for the reduction in driving force. This has a wider range of applications than previous equations. The model approach is validated using calcium oxide, widely used in, for example, environmental applications, alkali-initiated reactions, paint production, and mortar, mostly as a dissolved chemical. Despite the cumulative effect of all the errors associated with making predictions with data from various literature sources, especially diffusivity values, and of course the correlation itself, a fair agreement between experiment and prediction was obtained. This confirms that the regime of dissolution of calcium oxide is closely matched to the regime assumed in the derivation of the model. Overall, the results show that the framework for modeling the reduced driving force with time is a very effective way of improving understanding of the dissolution process to such an extent that it can give quantitative information to aid with the design of new mass transfer equipment or the optimization of existing equipment.