ABSTRACT
Polymers added to colloidal dispersions maintain stability or induce flocculation through a variety of mechanisms [1]. Bridging flocculation, relevant to technologies such as wastewater treatment and papermaking, is classically defined in Fig. 1 to result from interparticle attractions occurring when polymer chains simultaneously adsorb onto two particles. A number of systems are known to undergo bridging flocculation, including polyethylene oxide adsorbing onto clay [2], hydrophobically modified cellulosics and polyethylene oxides adsorbing onto acrylic latex [3], and certain cationic polyacrylamides adsorbing onto polystyrene latex [4-7], clay [8-11], silica [12,13], cellulose fibers [14-16], and aluminum oxide[17]. Generally, bridging is expected when small amounts of high-molecular-weight polymers are added to dispersions where they adsorb to the particles but do not saturate the surface[18]. Without a careful series of experiments, however, bridging flocculation can be hard to distinguish from other means of colloidal destabilization. Furthermore, bridging is sometimes a transient process occurring prior to stabilization of the suspensions.
