THE USE OF OPPOSITELY CHARGED POLYELECTROLYTES AS FLOCCULANTS AND RETENTION AIDS

New results for flocculation of cellulose-clay mixtures with a so-call ed dual system, consisting of the polycation poly(dimethyldiallylammon ium chloride), PDMDAAC, and different polyanions are presented. The fl occulation behaviour was investigated by different procedures: polyele ctrolyte titration, dewatering test, and measuring the residual turbid ity. It should be pointed out that the flocculation mechanism depends on the molecular weight of the polyanion used. In the first case, when the molecular weight of the polyanionic compound is relatively low, t he complexation between the polycation and the polyanion is said to be the mechanism and the ratio of anionic to cationic charges (n(-):n(+) ) is of crucial importance. Using a very high molecular weight polyani on (much greater than 1 million) as one component of the dual system, the mechanism of reaction consists of bridging and patch effects.