Polyelectrolyte Characteristics and Flocculation

Abstract

The relationships among the characteristics of cationic polyelectrolytes, mixing conditions, and flocculated particle size distribution were studied in an attempt to develop a rational basis for selecting polyelectrolytes. Charge density was found to be the predominant factor in selecting an optimum dosage of polyelectrolyte for flocculating particles with a primary charge opposite to that of the polyelectrolyte. The initial periods of both rapid and slow mixing are critical in the formation of flocs. Large, strong flocs were obtained with high‐molecular‐weight (>;105) polymers. A simplified model was developed to predict the average floc size based on the molecular weight of the polyelectrolyte and the mixing intensity.

Comparison of the performance of chitosan and a cationic polyacrylamide as flocculants of emulsion systems

“…Charge neutralization, can be considered, as the mechanism of flocculation by oppositely charged polymers; however, in same cases polymer bridging plays at least a minor role (19,20).…”

Characterization of kaolin flocs formed by polyacrylamide as flocculation aids

“…Previous research on the behaviors of adsorption and flocculation of particles had mainly focused on the complex effects of flocculation conditions on the removal efficiency, and thus, most of the experimental results were principally limited in the residual turbidity (Leu and Ghosh, 1988;Fan et al, 2000;Yu and Somasundaran, 1996), few investigations pay attention to distinction of floc itself. Knowledge of floc characteristics is essential for the optimization of flocculation process (Glover et al, 2001;Ray and Hogg, 1987;Yukselen and Gregory, 2004;Yu et al, 2006).…”

Treatment of anionic emulsion systems using chitosan, polyacrylamide, and aluminum sulfate

“…The presence of emulsified oil in waste water of the edible fats industry can interfere with many tertiary or advanced waste water treatments such as adsorption, filtration, and various membrane techniques (Ries and Meyers 1968) and can cause severe problems in the step of biological treatment (Axberg et al 1980). The destabilization of colloidal dispersions by polymers cannot be completely described by either mechanism: bridging and charge neutralization models (Leu and Ghosh 1988). The double-layer model predicts that the concentration of coagulant necessary to destabilize a colloid will be almost independent of the colloid concentration, and also that charge reversal and restabilization of the colloid cannot occur (Stumm and O'Melia 1968).…”