2-D and 3-D Interactions in Random Sequential Adsorption of Charged Particles

We explore the influence of electrolyte concentration on the adsorption of charged spheres using modeling techniques based on random sequential adsorption (RSA). We present a parametric study of the effects of double layer interactions between the charged particles and between the particle and the substrate on the jamming limit using a two-dimensional RSA simulation similar to that of Z. Adamczyk et al. (1990, J. Colloid Interface Sci. 140, 123) along with a simple method of estimating jamming limit coverages. In addition, we present a more realistic RSA algorithm that includes explicit energetic interaction in three dimensions, that is, particle-particle and particle-surface interactions during the approach of a particle to the substrate. The calculation of interaction energies in the 3-D RSA model is achieved with the aid of a three-body superposition approximation. The 3-D RSA model differs from the 2-D model in that the extent of coverage is controlled by kinetic rather than energetic considerations. Results of both models capture the experimentally observed trend of increased surface coverage with increased electrolyte concentration, and both models require the value of a key model parameter to be specified for a quantitative match to experimental data. However, the 3-D model more effectively captures the governing physics, and the parameter in this case takes on more meaningful values than for the 2-D model. Copyright 1997 Academic Press. Copyright 1997Academic Press

Electrophoretic Motion of Two Spherical Particles with Thick Double Layers

The electrophoretic mobilities of two interacting spheres are calculated numerically for arbitrary values of the double-layer thickness. A general formula for the electrophoretic translational and angular velocities of N interacting particles is derived for low-zeta-potential conditions. The present calculation complements the well-studied case of thin double layers. The results are compared with recent reflection calculations and are used to compute the O(phi) contribution to the electrophoretic mobility of a suspension. Particle interactions can be significant for values of the scaled particle radius kappaa