The use of dielectric spectroscopy for the characterisation of polymer-induced flocculation of core–shell particles

Flocculation is an important process in separation science, but only few methods are available for on-line evaluation of the process. Recently, it has been shown that dielectric spectroscopy can be used to characterise the flocculation process of hard polystyrene particles. As many “real life” suspensions contain particles covered with a porous layer of organic material, it is of interest to investigate the potential of dielectric spectroscopy to characterise the flocculation of such suspensions as well. In this paper dielectric spectroscopy is used to investigate the flocculation process of core–shell particles. The flocculation process is characterised using a photometric dispersion analyser as a reference method, and the results are compared to the dielectric dispersions measured by dielectric spectroscopy. It is found that the use of the relaxation time of the dielectric dispersion for an evaluation of the flocculation process is commensurate with the use of the photometric dispersion analyser. Furthermore, the magnitude of the dielectric dispersion is observed to decrease as the charge of the core–shell particles is neutralised. Dielectric spectroscopy is thus found to have potential as an on-line flocculation monitor.

The figure shows the dieelectric relaxation time of core–shell particles as a function of added polymer. The changes are caused by the collapse of the shell and the aggregation of the particles.Figure optionsDownload high-quality image (63 K)Download as PowerPoint slideResearch highlights
► Aggregation of core–shell particles causes an increase in the dielectric relaxation time.
► Charge neutralisation of core–shell particles results in a decrease in the magnitude of the dielectric dispersion.
► Aggregation of core–shell particles causes an increase in the magnitude of the dielectric dispersion.