Polyacrylamide (PAM) is a linear polymer known for its excellent thermal stability and water solubility. Due to its unique properties, it can also function as a coagulant aid.
When a coagulant is introduced into water, appropriate hydraulic conditions must be created to successfully complete the coagulation process. The coagulation process consists of two stages: mixing and flocculation. Each stage has different requirements for water turbulence. The mixing phase generally lasts less than two minutes, during which the coagulant must be stirred into the water to facilitate rapid hydrolysis and condensation reactions. In contrast, during the flocculation phase, turbulence should be reduced to prevent the flocs from breaking apart under prolonged high-intensity stirring.
When inorganic coagulants are combined with PAM, PAM’s inherent ability to aggregate fine polymer flocs is limited. Inorganic coagulants can easily become neutralized by electrostatic forces. Once aggregates reach a certain size, PAM can effectively perform its bridging function, enhancing the interaction between flocs through electrostatic neutralization, allowing them to come closer together and form larger, denser aggregates.
At this stage, PAM acts as a coagulant aid. It is a high molecular weight polymeric flocculant that stabilizes flocs through bridging adsorption. Fine, uniformly dispersed particles and clay particles in the dispersed phase are adsorbed onto the active groups on the carbon chains of PAM, forming aggregates that interconnect to create larger flocs.