Role of polymer conformation in interparticle-bridging dominated flocculation

Abstract

Flocculation of alumina with a dual polymer combination (polydiallyl dimethyl ammonium chloride and polyacrylic acid) is compared in this study with individual polymers. Zeta potential and conformational characteristics of the system are studied in order to determine the role of these properties in determining flocculation. The dual polymer system is shown to yield markedly better flocculation than either single polymer. Analysis of flocculation results along with the zeta potential measurements under corresponding conditions showed polydiallyl dimethyl ammonium chloride flocculation of alumina to be mainly electrostatic while polyacrylic acid flocculation to be polymer bridging at high pH and charge neutralization at low pH. The role of polymer conformation was found to be very important upon isolating the electrostatic effect by comparing the flocculation results under constant zeta potential. Polymer conformation in solution as well as at the solid-liquid interface can be altered by changing solution conditions and complexation with another polymer. It was shown that by manipulating polymer conformation, the flocculation can be greatly enhanced even at very low polymer dosage. In the specific case studied, the stretched and strongly adsorbed polymer was found to give excellent flocculation.