Polyacrylamide for Water Treatment CAS NO.9003-05-8

Superiority:

Polyacrylamide, an acrylic resin that has the unique property of being soluble in water. It is employed in the treatment of industrial and municipal wastewater.

Polyacrylamides are produced by the polymerization of acrylamide (C₃H₅NO), a compound obtained by the hydration of acrylonitrile. Acrylamide is usually dissolved in water; it has toxic effects on the nervous system and must be handled under special protective procedures. The dissolved monomers (single-unit molecules) are induced to polymerize (link together to form large, multiple-unit molecules) through the action of free-radical initiators. In the resultant polymer, the acrylamide repeating unit has the following structure:.

Polyacrylamide does not have the toxic effects of acrylamide monomer. The polymer is hydrophilic (displays an affinity for water) and can form aqueous solutions of very high concentration. Because of their gel-like properties, these solutions are employed as flocculants in the removal of suspended particles from sewage and industrial effluents (e.g., wastewater from paper mills). Through the highly reactive amide (NH₂) group, the polymer can be chemically modified to produce positively charged cationic polymer or negatively charged anionic polymer. Ionic polymers are especially useful in separating metals from residues in various mineral-processing and metallurgical operations.

APPLICATIONS

Poly(acrylamide-co-acrylic acid) and its sodium salts (APAM) are widely used as thickening agent, binder, super absorbent, soil conditioner, filtering aid, flocculating agent, crosslinker, suspending agent, lubricant, and oil recovery agent. One of its largest uses is waste water treatment. When added to waste water, it causes suspended particles to aggregate and to precipitate. In municipal and industrial waste water treatment it can be used in all liquid-solid separation processes including primary sewage treatment. PAMs are also used to treat water from mineral mining operations. Another common use is oil extraction and recovery. When water is injected into the well, PAM assists in pushing oil locked in reservoirs towards the pump by increasing the viscosity of the injected water.

Cationic polyacrylamides (CPAM) are used for emulsion breaking, and for promoting filtration and sludge dewatering. The primary use is wastewater treatment. As a primary organic coagulant, it neutralizes negatively charged colloidal particles and thus induces flocculation and sedimentation which reduces sludge volume. In paper mills, it is mainly used to enhance retention and dewatering.

Another low volume but important use of anionic and cationic polyacrylamides is gel electrophoresis for macromolecule separation. When an electric field is applied across a PAM gel, the (negatively) charged proteins or nucleic acids migrate across the gel away towards the positive electrode. Since the mobility depends on the charge and size of the molecules, each molecule species migrates differently through the gel matrix.