Effect of polyelectrolyte mixtures on the electrokinetic potential and kinetics of flocculation of clay mineral particles

The effect of binary mixtures of cationic and anionic electrolytes on the kinetics of aggregation, size and strength of flocs formed from kaolin and bentonite particles as a function of the polymer dose, mixture composition, sequence of the components addition and intensity of stirring the system has been studied. A synergism in the flocculation capacity in mixtures of moderate and weakly charged polyelectrolytes was observed; the biggest aggregates have been found at condition of adding first the cationic polymer then the anionic one. An initial intensive short stirring the suspension accelerates the aggregation process and increases the size of flocs independently of the sequence of polymers addition. In mixtures of cationic and anionic polyelectrolytes, the zeta-potential of particles is determined by the adsorbed anionic polymer independently of the charge density of polyelectrolytes and sequence of addition of the mixture components to the suspension. The laws observed were explained by features of polyelectrolytes conformation in adsorbed mixed polymer layers. (C) 2011 Published by Elsevier B.V.