Polyacrylamide, abbreviated as PAM, is classified into cationic, anionic and nonionic types. Its relative molecular mass ranges from 400 to 2000. The product appears as white powder and is highly soluble in water. It is prone to decomposition when the temperature exceeds 120 degrees.
Anionic polyacrylamide exhibits the characteristics of a polymer electrolyte in neutral and alkaline media. It is sensitive to salt electrolytes and can cross-link with high-valent metal ions to form insoluble gels. It is mainly used in domestic and industrial water treatment, industrial and urban sewage treatment, and can also be used for dewatering inorganic sludge.
The aqueous solution of cationic polyacrylamide is a high-molecular electrolyte with a positive charge. It can effectively coagulate suspended organic colloids and organic matter and enhance the solid-liquid separation process. Therefore, it is mainly used for the flocculation and sedimentation of suspensions and suspended solids in water, or the dewatering of organic sludge.
Nonionic polyacrylamide is a macromolecular chain without ionic groups, but the amide groups can form hydrogen bonds with many substances, such as clay and cellulose, and coagulate due to adsorption bridging.
In water treatment, the commonly used polyacrylamide is in the form of white powder granules, which are prepared into a 0.1% to 0.3% aqueous solution. The aqueous solution is uniform, transparent and viscous. When dissolving, anionic and cationic polymers need to be stirred for 1 to 1.5 hours, while nonionic polymers need to be stirred for 2 to 3 hours.
Principle of polyacrylamide flocculant
1.Polyacrylamide, due to its polar group - amide group, adsorbs on the surface of sediment particles through the action of its hydrogen bond.
2. Polyacrylamide has a very long molecular chain. The large orders of magnitude of long chains have an infinite adsorption surface area in water, so it has a good flocculation effect. It can use the long chains to bridge between particles, form large particle flocs, and accelerate sedimentation.
3. With the flocculation and coagulation assistance of polyacrylamide, during the sludge coagulation process of clear water treatment, double ionization compression may occur, which reduces the stability of particle aggregation. Under the action of molecular attraction, particles combine, and the simple anions of the dispersed phase can be replaced by the anion groups of the polymer.
4. The substances in the composition of polyacrylamide polymers and natural water, as well as the suspended solids in water, or the ions of previously added hydrolyzed coagulants, may undergo chemical interactions, which could be complexation reactions.
5. Polyacrylamide forms polymer Bridges between solid particles because its molecular chains are fixed on the surfaces of different particles.
