Flocculation properties and kinetic investigation of polyacrylamide with different cationic monomer content for high turbid water purification

A novel cationic polyacrylamide (PAMC) with various cationic monomer contents were prepared by copolymerizing acrylamide (AM) and methacryloxyethyl trimethyl ammonium chloride aqueous solution (DMC) through low-pressure ultraviolet (UV) initiation. The chemical structure of PAMC was determined by Fourier transform infrared (FTIR), proton unclear magnetic resonance spectrometry ( 1 H NMR), thermal gravimetric and differential analysis (TG-DTA) analysis. Flocculation performance of PAMC was tested in clarification of kaolin suspension, and flocculation kinetic and mechanism were discussed accordingly. Results showed that PAMC with 40% cationic monomer content exhibited excellent turbidity removal efficiency at pH 4.0, dosage of 0.3   mg·L −1 , stirring speed of 120   rpm, stirring time of 15   min, and sedimentation time of 40   min. Increased cationic monomer content and reduced kaolin pH level resulted in the increase of transmittance of the supernatant and decrease of optimal PAMC dosage. The determined kinetic constant ( K ) suggested that interaction of contact and collision between flocculants and kaolin particles was sufficient at the optimal PAMC dosage. ZP analytical results showed that charge neutralization and adsorption were dominant under acidic and alkaline environments, respectively.