Stimulated aggregation in ensembles of microcrystals

Aggregates of calcium carbonate microcrystals precipitated from a highly supersaturated aqueous solution were found to form in two stages. At the first stage, high-porosity disordered aggregates (floccules), and at the second, low-porosity ordered aggregates (agglomerates) formed. The application of an acoustic field with a frequency of 2.64 MHz and radiation power 3 W/cm² did not influence the kinetics of formation of microcrystals but accelerated aggregation by four orders of magnitude. This effect was explained by the sonostimulated desolvation of microcrystals colliding with the surface of aggregates and the corresponding decrease in the probability of the detachment from aggregates after collisions. The formation of microcrystals and aggregates in an acoustic field can be described by a Fokker-Planck-type equation. Taking this into account, a model of sonostimulated agglomeration revealing the direction of further investigations was formulated.