Here, increasing coverage both reduces the amount of in-We explore the influence of electrolyte concentration on the terfacial area available for adsorption and increases the proxadsorption of charged spheres using modeling techniques based imity of adsorbate molecules to one another, thereby making on random sequential adsorption (RSA). We present a parametric this situation more complex than the low coverage limit. study of the effects of double layer interactions between the Since high coverages are also of technological interest in charged particles and between the particle and the substrate on view of the more efficient use of adsorbent capacity, the the jamming limit using a two-dimensional RSA simulation similar development of effective and realistic approaches for modelto that of Z. Adamczyk et al. (1990, J. Colloid Interface Sci. 140,
ing this behavior is of great practical importance.
123) along with a simple method of estimating jamming limit
The most widely used basis for modeling adsorption is coverages. In addition, we present a more realistic RSA algorithm that includes explicit energetic interaction in three dimensions, that due to Langmuir, who considered adsorption to take that is, particle-particle and particle-surface interactions during place at individual, independent sites, each able to accommothe approach of a particle to the substrate. The calculation of date one adsorbate molecule. Consideration of reversible interaction energies in the 3-D RSA model is achieved with the mass action kinetics then led to the well-known hyperbolic aid of a three-body superposition approximation. The 3-D RSA isotherm. Experimental data from a very wide variety of model differs from the 2-D model in that the extent of coverage systems have been fitted to the Langmuir form despite clear is controlled by kinetic rather than energetic considerations. Redeviations, in many cases, from the assumptions inherent in sults of both models capture the experimentally observed trend of the Langmuir model. As a result, the parameters obtained increased surface coverage with increased electrolyte concentrain these studies have had only descriptive value in the curvetion, and both models require the value of a key model parameter fitting sense, and have not provided predictive mechanistic to be specified for a quantitative match to experimental data. Howcapabilities. Deviations of several kinds are possible: (i) ever, the 3-D model more effectively captures the governing physics, and the parameter in this case takes on more meaningful absence of clearly defined adsorption sites; (ii) deviations values than for the 2-D model.