A simple model to study the flocculation of suspensions over time

The model based on logistic growth theory, that was introduced in Chassagne, Claire, and Zeinab Safar. “Modelling flocculation: Towards an integration in large-scale sediment transport models.” Marine Geology 430 (2020): 106361, can be used to model the time evolution of either the particle (floc) size or the concentration of particles of a given size. In the present article, we show how this model can easily be linked to the many studies performed over the years about the flocculation kinetics at the onset of flocculation experiments. Flocculation experiments done on kaolinite suspensions destabilized by addition of salt are used as examples. Both perikinetic and orthokinetic flocculation are considered. By fitting the experimental data over the whole experiment period, it is shown that the floc size L(t) time evolution follows the relation dL/dt = L/t_b − L²/(L_eqt_b) where t_b is a characteristic time and L_eq a characteristic size, which are obtained from the fits.