Synergetic effect of cationic polymer microparticles and anionic polymer on fine clay flocculation

Although much research has been done into flocculation systems involving an ionic microparticles, few systematic investigations employing cationic poly mer microparticles (CPM) have been reported. In the present work, emulsifie r-free polymerization was conducted via copolymerization of styrene with th ree types of cationic monomer. This technique allowed cationic polymer micr oparticles with well-defined structures to be prepared. Dynamic flocculatio n experiments showed that the effectiveness of CPM alone as a flocculant fo r fine clay particles is affected by CPM charge density and by particle siz e, in the range 0.2 to 0.4 mu m. A strong synergetic effect between CPM and anionic polyacrylamide with high molecular weight and low charge density w as observed. This significantly reduced the dosage of polymeric flocculant required for effective flocculation. The best flocculation occurred at a va lue of the anionic polymer:CPM ratio of 1:8 (wt), with anionic polymer dosa ge approximately 0.06 wt% on clay. Electrostatic interaction between CPM an d anionic polymer appears to be an important driving force for flocculation . (C) 1999 Academic Press.