Design of Polyelectrolytes for use in Flocculation: Effect of Ionic Strength, pH, and Monomer Concentration on Reaction Kinetics and Copolymer Microstructure

Abstract

Flocculation is a technology used for removing contaminants from liquids in various processes, including municipal wastewater treatment. Minimal attention has been paid to controlling the polymer microstructure using polymer reaction engineering techniques. A method was developed to study copolymerization kinetics of AMPS – AAm using in situ 1H NMR. Altering the ionic strength of both AMPS – AAm and DADMAC – AAm comonomer solutions altered reactivity ratios and the resulting copolymer microstructure. From flocculation trials, it was found that varying microstructures improved flocculation performance. Next, two copolymerization models for design of experiments and reactivity ratio estimation were studied; it was found that the penultimate model may be more accurate. Finally, a 22 factorial design was employed for DADMAC – AAm copolymerization to understand effects of pH and monomer concentration on reactivity ratios, molecular weight averages, and flocculation performance. It was found pH and monomer concentration impacted copolymer microstructure, which in turn affected flocculation performance.