Kinetics of bridging flocculation. Role of relaxations in the polymer layer

Abstract

From experimental data on the kinetics of flocculation of polystyrene latex by means of poly(ethy1ene oxide) it is deduced that the well known classical aggregation theory of von Smoluchowski does not apply to bridging flocculation. A new kinetic model is therefore developed. It has as a key element the flattening of the polymer molecules with time, by which they lose the ability to form bridges. We take this into account by introducing a characteristic time of reconformation. The only other parameter is a minimum coverage of 'active' polymer chains per particle, necessary for bridge formation. Using reasonable values for these two parameters, we find that the model describes the experimental data very well.

Initial stage dynamics of bridging flocculation of polystyrene latex particles with low charge density polycation in a mixing flow near the isoelectric point

“…This transient condition continues for a while so that the rate of flocculation can be accelerated by "bridging". The picture is close to non-equilibrium flocculation proposed by Pelssers et al [48]. However, in our case, the charge of segments is opposite to the surface, as depicted in Fig.…”

Initial Stage Dynamics of Bridging Flocculation of Polystyrene Latex Spheres with Polyethylene Oxide

“…Because we could not find any differences with respect to ionic strength, we expect that the polymer layer formed by spreading is already thicker than 30 nm, which is the Debye reciprocal length for the experimental condition at the lower ionic strength (KCl = 1.0 × 10 −4 M). This fact also means that the theory of polymer inactivation by the folding of the protruding chain into the inside of the electrical double layer proposed by Pelssers et al (17) is not the case for our system. On the basis of the difference in the resulting layer thicknesses due to the means of polymer addition, Polverari and van de Ven (29) concluded that the adsorption of PEO onto PSL particles is kinetically controlled.…”

Mathematical modeling of polymer-induced flocculation by charge neutralization

“…Several experimental studies have shown that adsorption density reaches its maximum within a few minutes [34][35][36][37] and results in spontaneous growth of aggregates [38,39]. Polymer relaxation times were also found to be on the order of a few seconds or generally less than a minute [40,41]. Hence, it is reasonable to assume that polymer adsorption attains equilibrium before particles undergo any meaningful number of collisions.…”