Investigation of dynamic processing on aluminum floc aggregation: Cyclic shearing recovery and effect of sulfate ion

The floc formation and re-aggregation potential and the effects of sulfate on coagulation by AlCl3, polyaluminum chloride (PAC), and Al13 species using a photometric dispersion analyzer (PDA) are in- vestigated. It is found that the recovery level from shearing is the highest for the Al13 species. This is likely a result of increased collision efficiency due to more effective charge neutralization. The ex- perimental results show that sulfate has a significant effect on coagulation and promoting aggregation of hydrolyzed species for the Al13 species. It results in significant improvement of the coagulation effi- ciency through an electrostatic patch effect. The results further indicate that zeta potential of the parti- cle suspension is not the only indicator for the coagulant efficiency when precipitate formation sig- nificantly improves coagulation.