Brownian flocculation of polymer colloids in the presence of a secondary minimum.
Most analyses of Brownian flocculation apply to conditions where London-van der Waals attractive forces cause particles to be strongly bound in a deep interparticle potential well. In this paper, results are reported that show the interaction between primary- and secondary-minimum flocculation when the interparticle potential curve reflects both attractive and electrostatic repulsive forces. The process is highly time-dependent because of transfer of particles from secondary- to primary-minimum flocculation. Essential features of the analysis are corroborated by experiments with 0.80-microm polystyrene spheres suspended in aqueous solutions of NaCl over a range of ionic strengths. In all cases, experiments were restricted to the initial stage of coagulation, where singlets and doublets predominate.
Department of Chemical Engineering, University of Illinois, Urbana, IL 61801, USA. schow@uiuc.edu
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