Properties and quality indicators of polyacrylamide

Polyacrylamide, referred to as PAM, is divided into cationic, anionic, and nonionic types. The relative molecular mass is between 400 and 2000. The appearance of the product is white powder, soluble in water, and easy to decompose when the temperature exceeds 120 degrees.

Anionic polyacrylamide has the characteristics of a polymer electrolyte in neutral and alkaline media, is sensitive to salt electrolytes, and can be crosslinked with high-priced metal ions to form an insoluble gel. It is mainly used for domestic production water, industrial and urban sewage treatment, and can also be used for the dehydration of inorganic sludge.

The aqueous solution of cationic polyacrylamide is a polymer electrolyte with a positive charge. It can effectively condense suspended organic colloids and organic matter, and can strengthen the process of solid-liquid separation. Therefore, it is mainly used for the flocculation and precipitation of suspensions and suspensions in water, or the dehydration of organic sludge.

Nonionic polyacrylamide is a macromolecular chain that does not contain ionic groups, but the amide group can form hydrogen bonds with many substances, such as clay and cellulose, which condense due to adsorption and bridging.

In water treatment, polyacrylamide is usually used as white powdery particles, formulated into an aqueous solution of 0.1% to 0.3%, and the aqueous solution is a uniform, transparent and viscous solution.When dissolving, the anionic and cationic polymers need to be stirred for 1~1.5h, and the nonionic polymers need to be stirred for 2~3h.

Mechanism of action of polyacrylamide

The mechanism of action of polyacrylamide is generally considered to be adsorption-electrical neutralization-bridging, but electrical neutralization is not the main mechanism.In the process of flocculation, when the polymer concentration is low, the long chain of polymer adsorbed on the surface of the particles may be adsorbed on the surface of another particle at the same time, and two or more particles are linked together by bridging, resulting in flocculation. This is the bridging mechanism of polymer flocculation.The necessary condition for bridging is that there is a blank surface on the particles. If the concentration of polymer in the solution is large and the surface of the particles is completely covered by the adsorbed polymer, the particles will no longer flocculate through the bridging. At this time, the polymer plays a protective role.Therefore, there is an optimal range for the amount of polymer flocculant added, and beyond the optimal range, the flocculation effect is poor.