UNDERSTANDING ADHESION - A MEANS FOR PREVENTING FOULING

Adhesion of particulate materials is an important step in the formatio n of fouling. Because the size of such materials is generally less tha n 1 mu m the phenomenon can be described in terms of colloid chemistry . Accordingly, the net force of interaction between foulants and the s urface has been described in terms of DLVO theory (van der Waals attra ction and electrostatic double-layer repulsion). However, those forces are sometimes not sufficient to describe the formation of fouling. Re cent works have made it possible to calculate the effect of hydrophobi c interactions and steric forces, which can also be taken into account . In aqueous media, the various types of interactions can be strongly affected by the pH, the ionic strength, the type of ions, and the pres ence of polymeric molecules. The objective of this work is to give a g eneral overview of the basic physicochemical factors playing a role in fouling and to outline some practical aspects related to the theoreti cal reasoning to help prevent or at least mitigate fouling. (C) Elsevi er Science Inc., 1997.