A model for the collision efficiency of shear-induced agglomeration involving polymer bridging

An expression is derived in terms of key dimensionless groups, including a group for steric interaction, to determine the collision efficiency for shear-induced agglomeration of non-colloidal particulate suspensions. Agglomeration is assumed to take place due to bridging of polymer layers on colliding particles. The forces considered arise due to the van der Waals, double-layer, steric and hydrodynamic interactions. The expression for collision efficiency was determined a priori from physico-chemical parameters including the shear rate and it shows the dependence on flocculant concentration, molecular weight and shear rate. A cone and plate device was used to experimentally study the agglomeration of spherical glass beads dispersed in an aqueous glycerin solution. Non-ionic polyethylene oxide (PEO) was used as a flocculant. The collision efficiency was found to have a power law dependence on shear rate and be a strong function of adsorbed polymer layer thickness.