Co-Flocculation of Mixed-Sized Colloidal Particles in Aqueous Dispersions Under a DC Electric Field.

When an electric field is applied to or removed from colloidal particle aqueous dispersions, a reversible increase in sedimentation velocity of the colloidal particles, referred to as the Electrically Induced Rapid Separation (ERS) effect, is observed. While electrophoresis and other interfacial electrokinetic phenomena under applied electric fields are well-studied, the phenomena of particle aggregation and re-dispersion caused by the application and removal of the field remain largely unexplored despite their significance. Experiments using mixed aqueous dispersions of poly (methyl methacrylate) (PMMA) particles of different sizes revealed that applying an electric field induced the formation of co-flocs involving both large and small particles, significantly enhancing the sedimentation velocity. It was also observed that slight vibrational deformation hindered the ERS effect. Under uniform electrolyte concentration conditions, the ERS effect was found to depend on pH, with a stronger effect observed when the absolute value of the zeta potential was larger. These findings indicate that the presence of the electric double layer plays a crucial role in the manifestation of the ERS effect. The results of this study provide critical insights for the further application of the ERS effect.