Assessing Polyelectrolyte Behavior by Size‐Exclusion Chromatography

Abstract

Size‐exclusion chromatography (SEC) is used to investigate the behavior of polyelectrolytes during sewage and water‐treatment processes. Sewage treatment is modeled by jar tests on raw sewage. Beyond the optimum polyelectrolyte dose for turbidity removal of 2 mg/L, SEC is able to detect residual polyelectrolytes in the supernatant. It is also possible to show by SEC measurements that higher molecular weight (MW) fractions of cationic polyelectrolytes are adsorbed to the solids proportionally more than the lower MW fractions; however, with anionic polyelectrolytes there is no similar selection. In the case of water treatment, SEC is used to investigate the interaction of polyelectrolytes with chlorine and ozone. In both cases, there is a shift to lower MW products, and this could be related to a reduction in flocculation efficiency of the polyelectrolyte. The production of acrylamide and chloroform during chlorine and ozone interaction with the polyelectrolyte is also monitored. Acrylamide monomer concentration is reduced by both chlorine and ozone. Chloroform is produced in significant concentrations during chlorination (yield of 0.019 mg/mg at pH 9 after three days). SEC can thus be used for detection, monitoring, and control; to study the behavior of polyelectrolytes during treatment processes and hence design more effective polyelectrolytes; and finally, to predict the flocculation efficiency of existing polyelectrolytes.