ELECTROPHORETIC PARTICLE AGGREGATION

Stability criteria and pairwise aggregation rates have been calculated for electrophoretic motion of non-Brownian spheres with differing zet a potentials and thin electric double layers. Aggregation rates are ob tained by a trajectory analysis, and stability criteria are determined by analyzing the near-contact motion between two particles. The resul ts predict that a given suspension is considerably less stable against aggregation during electrophoresis than during sedimentation, and tha t the aggregation efficiencies for electrophoresis exceed those for bu oyancy-driven motion by an order of magnitude. These results are expla ined in terms of the relatively weak interaction between well-separate d particles during electrophoresis and the electrically driven withdra wal of fluid between closely spaced particles in an electric field. El ectrophoretic and buoyancy-driven aggregation rates depend primarily o n a dimensionless driving force and the size ratio of the particles; t he stability of a colloidal suspension depends on four additional para meters that describe the colloidal forces that act between the particl es. (C) 1995 Academic Press, Inc.