Flocculation and Retention of Precipitated Calcium Carbonate by Cationic Polymeric Microparticle Flocculants

Abstract

A series of cationic polymeric microparticles (CPMP) with different charge densities and particle sizes were synthesized using emulsion or microemulsion polymerization. The interactions among positively charged polymeric microparticles, negatively charged fibers, and precipitated calcium carbonate (PCC) particles were studied. It has been found that although CPMP could adsorb onto a positively charged PCC particle surface, effective flocculation of PCC in water could not be obtained by CPMP alone. However, the combination of CPMP with an anionic polyacrylamide (APAM) did significantly improve the flocculation of PCC. The flocculation mechanics of PCC in this dual flocculation system were that the CPMP first created effective patches on the PCC surface, then APAM formed interparticle bridges through positively charged CPMP patches. It has also been found that the particle size and the surface charge of CPMP are two major factors affecting the flocculation of PCC suspension. The retention of PCC on wood fibers using a dual-flocculant system of CPMP–APAM was studied, and the related mechanism is discussed here.