Kinetics of Polymer Conformational Changes and Its Role in Flocculation

Abstract

The kinetics of conformational changes of a series of partially hydrolyzed polyacrylamides (HPAM) adsorbed on alumina in aqueous solutions was studied along with the flocculation of alumina. After the polymer was adsorbed, the conformation of the adsorbed polymer was changed by shifting the suspension pH. It was found that the kinetics of the polymer conformational change was dependent upon the hydrolysis degree and the molecular weight. It was found that while under fixed pH conditions the flocculation continuously decreased apparently due to floc breakage; under shifted pH conditions (from low to high) it went through a maximum as a function of time. When the effects of floc breakage caused by agitation are isolated and accounted for the flocculation is found to correlate well with the conformational changes in the system. It is proposed that the unusual flocculation time dependence obtained under the shifted pH condition is caused by the combination of the beneficial effect of the predominant polymer conformational changes and the detrimental effect of floc breakage by agitation.