Colloids and Surfaces A: Physicochemical and Engineering Aspects 138 (1998) 207–216 The capture of colloidal particles on surfaces and in porous material: basic principles Theo G.M. van de Ven Paprican and Department of Chemistry, Pulp and Paper Research Centre, McGill University, Montreal, H3A 2A7, Canada Abstract The deposition of colloidal particles onto surfaces can be considered a special case of hetero-coagulation. Deposition and detachment kinetics are determined by a combination of colloidal and hydrodynamic factors. For well-defined geometries and for systems in which particle–wall interactions are attractive, the deposition rate can be predicted accurately from first principles. When repulsive interactions are operative, theoretical difficulties arise from a number of sources, such as a coupling between hydrodynamics and electrokinetics, surface charge regulation, and shear- induced modification of configurations of adsorbed polymers. These complications prevent accurate prediction of slow deposition rates. Also, no good a priori models exist to predict detachment rates, although trends can be predicted. Experimental examples will be provided of colloidal particle deposition on flat surfaces in an impinging jet, in which the flow is well defined, and in porous beds consisting of pulp fibers, in which the flow is rather ill defined. Effects of electrolyte and polymers on deposition are discussed. © 1998 Elsevier Science B.V. Keywords: Particle deposition; Deposition kinetics; Impinging jet; Packed beds 1. Introduction improve our fundamental understanding of such systems. Deposition of colloidal particles on surfaces is The kinetics and detachment of colloidal par- important in a number of areas, such as in paint- ticles is determined primarily by two factors: (i) ing, printing, coating, filling of paper, adhesion of the ‘‘chemistry’’, which determines the attractive biological cells and fouling of membranes. In some or repulsive forces between particles and the sur- applications deposition is being promoted, in some face, as well as the strength of the adhesive bond, applications deposition is being avoided or mini- and (ii) mechanical or hydrodynamic forces and mized, whereas in others the detachment of colloi- flow fields, which determine the rate at which dal particles is desired, e.g. as in the deinking of particles are transported to and from the surface. waste papers. In all cases the process is controlled Hence, to study particle–wall interactions it is by the deposition and detachment kinetics of col- essential to control both physicochemical and loidal particles on surfaces. It is clear that a hydrodynamic conditions. thorough understanding of the kinetics is essential A number of deposition-flow cells have been if one wants to optimize a process involving depos- used by various researchers to study deposition ited particles. At the same time, the study of model kinetics, such as the parallel plate channel [1,2], the rotating disk [3,4], and the Couette flow cell systems and their interactions with surfaces can 0927-7757/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S0927-7757(96)03956-8