Kinetics bridging flocculation

Stoll, S. and Buffle, J. (1996). Computer simulation of bridging flocculation processes the role of colloid to polymer concentration ratio on aggregation kinetics. J. Colloid Interface ScL, 180,548-563. 

This book presents coverage of the dynamics, preparation, application and physico-chemical properties of polymer solutions and colloids. It also covers the adsorption characteristics at and the adhesion properties of polymer surfaces. It is written by 23 contemporary experts within their field. Main headings include Structural ordering in polymer solutions Influence of surface Structure on polymer surface behaviour Advances in preparations and appUcations of polymeric microspheres Latex particle heterogeneity origins, detection, and consequences Electrokinetic behaviour of polymer colloids Interaction of polymer latices with other inorganic colloids Thermodynamic and kinetic aspects of bridging flocculation Metal complexation in polymer systems Adsorption of quaternary ammonium compounds art polymer surfaces Adsorption onto polytetrafluoroethylene from aqueous solutions Adsorption from polymer mixtures at the interface with solids Polymer adsorption at oxide surface Preparation of oxide-coated cellulose fibre The evaluation of acid-base properties of polymer surfaces by wettability measurements. Each chapter is well referenced. 

Pelssers, E.G.M., M.A.C. Stuart, and G.J. Fleer. 1990. Kinetics of bridging flocculation—role of relaxations in the polymer layer. Journal of the Chemical Society, Faraday Transactions 86 (9) 1355-1361. 

The two major theories of flocculation, the bridging model (1) and the electrostatic patch model (2, 3 ), provide the conceptual framework for the understanding of polymer-aided flocculation, but they do not directly address the kinetics of the process. Smellie and La Mer (4) incorporated the bridging concept into a kinetic model of flocculation. They proposed that the collision efficiency in the flocculation process should be a function of the fractional surface coverage, 0. Using a modified Smoluchowski equation, they wrote for the initial flocculation rate... 

Stock composition, kinetics of adsorption and hydrodynamic shear dictate the point at which a cationic polymer is added to a papermaking furnish in order to induce flocculation. Flocculation of cellulose fibers in turbulent flow proceeds very rapidly and is completed in less than two seconds.120-123 Flocks form due to charge interactions through a patch-type or a bridging-type mechanism. However, these flocks will be sensitive to shear force and deflocculation and reflocculation might occur. 

As mentioned above, two-component flocculants often present advantages over a single-component flocculant, such as better control of flocculation kinetics and improved floe strength. Most dual-component flocculants consist of two polyelectrolytes, two pol5miers, or a polyelectrolyte and a nanocolloid. Usually, one of the components adsorbs on the surface of the particles to be flocculated and the second component bridges these polymer-coated particles. Therefore, this combination of patching and bridging is believed to be responsible for excellent results, as described for instance for retention systems (Fig. 5) [10]. 

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