Polyelectrolyte coagulant and flocculant effects on heteroagglomeration of cellulosic fines and CaCO_3 particles

摘要

Effects of a high-charge cationic polyelectrolyte (a coagulant), a very-high-mass cationic polyelectrolyte (a flocculant), or the combination of a cationic coagulant followed by an anionic flocculant were evaluated relative to the particle size distributions in suspensions of cellulosic fines and CaCO_3 particles. Laser diffraction particle size analysis for the mixed suspension showed the virtual disappearance of signal corresponding to unattached CaCO_3 particles upon addition of cationic flocculant. Charge effects related to the coagulant had less influence on the particle size distribution compared to the polymer bridging effects of the flocculant. Microscopic images revealed differences in the structure of agglomerates in the polymer-treated systems. The polymer-induced attachments between CaCO_3 and cellulosic fines can be interpreted as an additional stage of heteroagglomeration, supplemental to those attachments that had already been formed between CaCO_3 and cellulose surfaces prior to addition of the polyelectrolytes. Resulting structures depended not only on the polyelectrolytes but also on the characteristic shapes of cellulosic fines and the fibrillation of their surfaces.