ABSTRACT
Surface contamination due to submicrometer particulate matter is of concern in many areas including silicon wafer fabrication, mineral processing, water purification and detergency. The permanent removal of these particles from surfaces is a critical factor in these processes [1]. In solution, the combined effects of van der Waals attractive forces and electrical double layer forces govern the interaction between particles and a surface. By varying the solution conditions it is possible to alter the surface chemistry of interacting materials and change their interaction from attractive to repulsive. In this work, the attachment and detachment of
nanosized silica particles onto titanium dioxide surfaces has been studied as a function of pH and addition of solutions of linear polyphosphates. Previous in-situ infra-red studies [2] have shown that linear polyphosphates selectively adsorb onto titanium dioxide forming strong chemical bonds. Streaming potential measurements [3] have shown that for a fixed polyphosphate concentration, the titanium dioxide becomes more negative with increasing n, which was attributed to an increased charge density with n. In addition, direct force measurements [3-5] have shown that adsorbed polyphosphate introduces a steric layer which leads to a short-ranged repulsive interaction.
