Effect of polyelectrolytes and polyelectrolyte mixtures on the electrokinetic potential of dispersed particles. 1. Electrokinetic potential of polystyrene particles in solutions of surfactants, polyelectrolytes and their mixtures

Abstract

The effect of cationic and anionic surfactants, as well as cationic and anionic polyelectrolytes (PE), their binary mixtures on the electrokinetic potential of monodisperse carboxylated polystyrene (PS) particles as a function of the reagents dose, pH, the charge density (CD) of polymers, the surfactant/PE and binary PE mixture composition, and sequence of components addition to the suspension has been studied. It has been shown that addition of increasing amount of anionic surfactant/polyelectrolytes increases the abso lute value of the negative zeta potential of PS particles; this increase is stronger the CD of the PE and pH of the system are higher. Adsorption of cationic surfactant/polyelectrolytes leads to a significant decrease in the negative ζ potential and to overcharging the particles; changes in the ζ potential are more pronounced for PE samples with higher CD and for suspensions with lower pH values. In mixtures of cationic and anionic PE, in a wide range of mixture composition, the ζ potential of particles is determined by the adsorbed amount of the anionic polymer independently of the CD of PEs and the sequence of addition of the mixture components. The isoelectric point of the surface is reached at the adsorbed amount of positive charges of PE that is approximately equal to the surface CD of particles. The laws observed were explained by features of macromolecules conformation in adsorbed mixed PE layers. Considerations about the role of coulombic and non coulombic forces in the mechanism of anionic/cationic PE adsorption are presented.

Polymer adsorption and electrokinetic potential of dispersed particles in weak and strong electric fields

“…roughly the same as the surface charge density. Similar results were obtained for other polyelectrolytes adsorbed on the surface of silica and polystyrene [50][51][52].…”

“…Similar behaviour we observed for all investigated particles having adsorbed cationic polymers of different charge density [48][49][50][51][52][53]. Effect of pH on the electrokinetic potential of polyelectrolyte-covered particles is illustrated by Fig.…”

“…We have performed a systematic study on the effect of anionic and cationic polyelectrolytes on the electrokinetic potential of negatively charged polystryrene, silica, bentonite and kaolin particles as a function of the polymer dose, pH, charge density (CD) of the polyelectrolyte, electrolyte concentration [48][49][50][51][52][53]. It should be stressed that our independent adsorption measurements testify that in the PE concentration range described in this section, the whole added polymer is adsorbed by particles, i.e.…”

“…We have shown [50][51][52] that there is a remarkable correlation between the number of (+) charges of polyelectrolytes with different CD that is necessary to add to polystyrene or silica suspension to reach the iep of the particles surface. For example, for SNF FO 4125 (CD=6 %), SNF FO 4400 (CD=35 %) and SNF FO 4800 (CD=80 %) cationic polyelectrolytes, the iep of the PS surface is reached at polymer concentrations 3.2 mg/g, 0.6 mg/g and 0.25 mg/g, respectively, i.e.…”

“…This is explained by formation of pseudo-cationic polyelectrolyte from the anionic one as a result of H + transfer from the solution to the amino-group of the polymer in highly acidic solutions (pH 2.1) [52].…”