Flocculation Kinetics of Colloidal Suspensions: Effects of Metallic Coagulant Dosage and Primary Particle Concentration on the Breakup and Aggregation Constants

Abstract

The scientific knowledge of the flocculation process has progressed substantially since the experimental work of Argaman and Kaufman (1970). However several aspects, particularly the ones associated with process mathematical modeling, still remain controversial. One of these controversies surrounds the effect of coagulant dosage and the concentration of primary particles on the aggregation and breakup kinetic constants, K_A and K_B, respectively. In this study, the experimental data collected to evaluate this effect showed that: (a) The dosage of metallic coagulants influences considerably the flocculation kinetics of colloidal suspensions, reflecting directly on K_A and K_B; (b) For short detention times, in order to allow for adequate aggregation of colloidal particles, the coagulant dosage should be the one which produces the largest possible K_A; for relatively longer detention times, the dosage can be smaller, leading to the sweep coagulation mechanism. In this case the coagulant dosage is actually defined by flocculation and not by coagulation.