Bridging efficiency, flocculation

The two major theories of flocculation, the bridging model (1) and the electrostatic patch model (2, 3 ), provide the conceptual framework for the understanding of polymer-aided flocculation, but they do not directly address the kinetics of the process. Smellie and La Mer (4) incorporated the bridging concept into a kinetic model of flocculation. They proposed that the collision efficiency in the flocculation process should be a function of the fractional surface coverage, 0. Using a modified Smoluchowski equation, they wrote for the initial flocculation rate... 

High shear forces are prevelant in the approach flow system to the paper machine (i.e. as the fibre suspension approaches the point of deposition on the wire), and these have a large impact upon the efficiency of retention aids (Figure 7.8). A study of the effect of shear can often be helpful in establishing the mechanism of retention. Bridging flocculation is irreversibly sensitive to shear (i.e. when the shear forces are removed the suspension does not reflocculate) whereas charge neutralisation is reversibly sensitive to shear. 

I. Particle size vs. chain length and dissociation property of the polymer For flocculation of coarse particles, bridging by organic polymers is very effective, especially that by the nonionic polymer. Inorganic electrolyte and surfactants do not have high flocculation efficiency. 

Schmitt, A., M.A. Cabrerizo-Vflchez, R. Hidalgo-Alvarez, and A. Femandez-Barbero. 1998. On the identification of bridging flocculation An extended collision efficiency model. Progress in Colloid and... 

---