The flocculation of kaolin aqueous dispersion by two cationic polyelectrolytes

The flocculation by compositions, based on synthetic poly-1,2-dimethyl-5-vinylpyridinium methyl sulfate (K1),poly-trimethyl(methacryloyloxyethyl)-ammonium methyl sulfate (K2) and natural polyelectrolyte (chitosan, Cs) using an aqueous kaolin dispersion was studied. Floccule formation parameters and sedimentation rates were determined by optical microscopy, turbidimetry and microelectrophoresis. The synergistic effect is observed using the polyelectrolyte compositions, it appears in 40% increase of the floccule sedimentation rates and promotes the formation of two times more dense floccules compared to using individual flocculants. The synergistic effect of two cationic polyelectrolytes was confirmed by the flocculation research results in aqueous-salt solutions at various NaCl salt concentrations. A study of the behavior of the two polyelectrolytes macromolecules in solution was performed to explain the observed synergistic effect. The decrease of macromolecules hydrodynamic radius in the joint presence of two like-charged polyelectrolytes was revealed by the capillary viscometry, dynamic and static light scattering. It was determined, that the behavior of two cationic polyelectrolytes in the common solution determines the character of their behavior on the dispersed phase surface in the flocculation process.