FLOCCULATION OF ILLITE SUSPENSIONS BY CAT IONIC POLYELECTROLYTES

The adsorption of cationic polyelectrolytes (PE) and its effect on the electrophoretic mobility of illite particles and on the stability of their suspensions have been studied. It has been shown that the adsorp tion isotherms of polymers are of high-affinity type, and the adsorbed amount substantially reduces with the solid phase concentration. The adsorption of polyelectrolytes first decreases the electrokinetic pote ntial of the particles, then causes the recharging of the particles su rface. The dependence of the sedimentation (filtration) rate of suspen sions on the PE concentration reveals a maximum. The concentrations of highly charged PE at which maximum flocculation occurs and those corr esponding to the isoelectric point (iep.) of the surface, coincide, wh ereas for PE with low charge density, intensive aggregation takes plac e at polymer contents much less than that necessary to reach the iep. value. Different mechanisms of flocculation were assumed in the presen ce of low and high charge density polyelectrolytes. Also the role of e quilibrium and non-equilibrium adsorbed layers on the mechanism of flo cculation of dispersions with different solid content is discussed.