Probing Coagulation and Fouling in Colloidal Dispersions with Viscosity Measurements: In Silico Proof of Concept

Colloidal dispersions in a flow can undergo the unwanted processes of coagulation and fouling. Prevention of these processes requires their proper understanding and the ability to monitor their extent. Currently, neither of these requirements is sufficiently fulfilled and this motivates the development of detailed models that capture the nature of the dispersion processes operating at the scale of primary colloidal particles. We model coagulation and fouling in colloidal dispersions using the dynamic discrete element method (DEM), with an interaction model accounting for particles that are elastic, adhesive, and stabilized by electrostatic charge. At the same time, the particles can adhere to the wall. Flow-field computation captures the mutual influence between particles and flow. The model also includes a pair-wise implementation of lubrication forces. The modeling results indicate that viscosity is highly sensitive to the formation of clusters, reflecting not only the larger size of clusters with increasing surface energy, but also the slower kinetics of coagulation in charge-stabilized dispersions. By contrast, viscosity is not sensitive to the attachment of particles to the wall. The mechanism of fouling determined from the simulation results comprises the initial bulk formation of clusters and subsequent dynamic wall attachment and detachment of the clusters. The presented work improves understanding of the dynamic behavior of colloidal dispersions, which is strongly relevant for industrial applications as well as for on-line monitoring and control.