The use of dielectric spectroscopy in the investigation of the effect of polymer choice on the flocculation of polystyrene particles

The flocculation of colloidal suspensions using synthetic polymeric flocculants is an important operation in separation processes. Optimizing flocculant use requires insight into the underlying mechanisms governing flocculation. As most existing methods for the online characterization of flocculation processes can only be used on dilute suspensions, new methods applicable at high solid content levels are of interest. This study used dielectric spectroscopy to investigate the mechanisms involved in the flocculation of polystyrene particles with three different cationic polymers. We observed that the relaxation time of the dielectric dispersion increased as particle flocculation was initiated. Reduction of particle charge due to polymer addition was found to reduce the magnitude of the dielectric dispersion, whereas the formation of aggregates increased it. This resulted in decreasing magnitude when charge reduction was the primary cause of flocculation, whereas the magnitude increased when the particles were flocculated by bridging.

Theoretical permittivity spectrum of a suspension consisting of (1) primary particles, (2) open aggregates and (3) compact aggregates. Frequency window of the measurement of dielectric spectroscopy is indicated.Figure optionsDownload as PowerPoint slide