The use of a particle counter in studying flocculation by polymers

An investigation has been made into the flocculation of colloidal particles by polymers in solution at different polymer molecular weights, and particle size and concentrations. The systems studied were, initially kaolin with polyacrylamide, and, more extensively, polystyrene latexes with a cationic polyelectrolyte. The flocculation was followed by counting the particles using a laser-light-scattering flow ultramicroscope. The results have been explained in terms of both charge neutralisation and reversal, and polymer bridging between particles. Unusual features were observed when using the polyelectrolyte where flocculation, restabilisation and secondary flocculation at increasing polymer doses were found. Tentative explanations for these results have been put forward.