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Bridging Flocculation : A Modeling Study of the Role of Polymer Adsorption Dynamics

Anand V. P. Gurumoorthy and V. A. Juvekar

Polymer adsorption from solution to solid surface plays an important role in bridging flocculation. It is desirable to understand the dynamics of adsorption for a number of reasons. For example, the balance between flocculation and stabilization of a colloidal suspension can be affected by the dynamics of adsorption. Although a number of experimental studies on kinetics of polymer adsorption have been reported in the literature, there is a need for a comprehensive model for diffusion in the interfacial region. Such a model is proposed in this paper. The connectivity of the homopolymer segments is assumed to be described by a random flight model within the framework of mean field theory while the dynamics of the probability of the connected segment is given by the Smoluchowski equation. The model yields the profiles for evolution of surface excess with time. This is then compared with surface excess obtained from equilibrium calculations. It is found that the surface excess predicted by the dynamical model at long times is the same as that predicted by equilibrium calculations. The dynamical adsorption behavior of homopolymers of different chain lengths is also studied. It is found, as expected, that longer chains adsorb more than the smaller chains and tend to equilibrate slower than smaller chains.