A micro-mechanical model for the rate of aggregation during precipitation from solution

Abstract

This paper collates approximately 10 years of research by our group on the subject of aggregation during precipitation of inorganic salts from aqueous solutions. We show that by considering the aggregation rate constant to be the product of a collision rate constant and an efficiency we may describe all our results (for one vessel) as a dependence of the efficiency on a dimensionless number, M. The formulation of M arises from our previously published hypothesis that new aggregates must cement themselves together fast enough to withstand the (periodic) hydrodynamic force acting to disrupt them. The new analysis presented here shows that our previous deduction of an internal mass transfer limit in the cementing process is incorrect. We are, by means of this analysis, now able to propose simple, physically based, and apparently general, kinetic equations for aggregation.