SOME EFFECTS OF PARTICLE-SIZE IN SEPARATION PROCESSES INVOLVING COLLOIDS

The size of colloidal particles has long been considered to be a major factor in their mass transport in aquatic environments. In aggregatio n and deposition reactions, the mass transport rates of colloidal part icles are expected to decrease with increasing particle size since the rmal diffusion dominates this process. Particle size has also been con sidered to affect colloid chemical interactions, at least on theoretic al grounds, with predicted rates of attachment in aggregation and depo sition processes decreasing substantially as colloidal particle size i s increased. Observations have failed to confirm this prediction. The situation becomes more complex and predictions more consistent with ob servations when reversible aggregation and deposition such as dan occu r in secondary minima are considered. This is done in this paper in si mulations using a combination of Brownian dynamics and Monte Carlo (BD MC) techniques. Some experimental observations of virus transport in p orous media are presented. The BDMC simulations provide a partial expl anation for these results. (C) 1997 IAWQ. Published by Elsevier Scienc e Ltd.