Do cationic and anionic polyacrylamide settling rates increase with charge density?

The maximum settling rates of flocs produced by cationic and anionic polyacrylamides decrease with charge density and increase with molecular weight.

What are cationic polyelectrolytes?

Polyacrylamides were used extensively as a flocculant in the clarification of water in industrial and municipal processes (5). Cationic polyelectrolytes are a class of polyelectrolytes that derive their unique properties from the density and distribution of positive charges along a macromolecular backbone as well as molecular weight.

Why do cationic polyacrylamides flocculate negatively charged particles?

The flocculation of negatively charged fine particles by high molecular weight cationic polyacrylamide occurs by the adsorption of the polyacrylamide chains on to the particle surface. Thus charge neutralization becomes a major mechanism, where the cationic polyacrylamides will locally reverse the particle surface charge.

How do cationic polyacrylamides aggregate?

Thus charge neutralization becomes a major mechanism, where the cationic polyacrylamides will locally reverse the particle surface charge. Collision with negative patches on another particle allows bridging then aggregation .

How does cationic polyacrylamide reduce zeta potential?

The reduction in the zeta potential to zero by the cationic polyacrylamide arises from charge neutralization through electrostatic attraction between the positively charged polymer and negative surface sites of the particle, and the adsorption of large amount of positively polymer onto the surface of kaolinite gives rise to charge reversal.

Does molecular weight affect thermal stability of polyacrylamide?

The very high molecular weight polyacrylamide displayed the highest stability in the series, indicating the importance of the molecular weight for thermal stability. On the other hand, very low molecular weight polyacrylamide displayed the lowest stability. The increase in molecular weight caused a decrease of weight loss %.