Transient collision efficiency of polymer-induced flocculation

Abstract

The temporal variation of the collision efficiency of primary particles in polymer-induced flocculation is investigated. A kinetic model is introduced assuming that the flocculation and the adsorption of polymer molecules are second order, and the desorption of polymer molecules is first order. The adsorption of polymer molecules is assumed to be reversible, and an adsorbed polymer molecule is allowed to rearrange itself. The result of numerical calculations reveals that, depending on the ratio (number of sites on the polymer molecules/number of sites on the surfaces of the colloidal particles) and the relative magnitude of the adsorption rate constant and the desorption rate constant, the collision efficiency calculated by the conventional analysis may be either underestimated or overestimated. Thus, care must be taken in predicting the rate of polymer-induced flocculation through the collision efficiency approach.