2-D AND 3-D INTERACTIONS IN RANDOM SEQUENTIAL ADSORPTION OF CHARGED-PARTICLES

We explore the influence of electrolyte concentration on the adsorptio n of charged spheres using modeling techniques based on random sequent ial adsorption (RSA). We present a parametric study of the effects of double layer interactions between the charged particles and between th e particle and the substrate on the jamming limit using a two-dimensio nal RSA simulation similar to that of Z. Adamczyk et al. (1990, J. Col loid 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 dimen sions, that is, particle-particle and particle-surface interactions du ring the approach of a particle to the substrate. The calculation of i nteraction energies in the 3-D RSA model is achieved with the aid of a three-body superposition approximation. The 3-D RSA model differs fro m the 2-D model in that the extent of coverage is controlled by kineti c 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 th e governing physics, and the parameter in this case takes on more mean ingful values than for the 2-D model. (C) 1997 Academic Press.