Comparison of coagulation mechanism between powdered activated carbon and kaolin suspensions with cationic polyelectrolytes

In this study, a cationic polyacrylic polymers was used as a primary coagulant to investigate the difference of coagulation mechanism between powdered activated carbon(PAC) and kaolin suspensions by Jar test. The origins of surface charge on PAC and kaolin are the dissociation of surface functional groups and the isomorphous replacement within the crystal lattic, respectively. Owing to containing different origins of surface charge on particles, coagulation of PAC suspensions is markedly different from that of kaolin suspensions. Coagulation mechanism with polymers is predominated by bridging action. The mutual interactions responsible for bridging action are hydrogen bonding and ionic bonding, and are dependent of the types and concentrations of particle, and polymers dosage. For particle concentrations less than 100 mg/l, the coagulation of PAC suspensions could be occurred with polymers, but kaolin suspensions.