Ionic adsorption from a primitive model electrolyte—nonlinear treatment

In order to investigate the effects of both finite ion size and specific adsorption on the electrical double layer, we consider a restricted primitive model elecrolyte against a uniformly charged nonpolarizable surface, in which the ions adsorb on the wall via Baxter’s sticky potential. Wall–ion interactions are treated in the hypernetted-chain (HNC) approximation and bulk interactions are treated in the mean spherical approximation (MSA). In the HNC/MSA, this model does not exhibit any saturation in the adsorbed surface charge density although one can be produced as an artifact of linearization. The expression for the potential of mean force possesses the term previously identified as responsible for the discreteness-of-charge effect, although there is a quantitative difference due to the absence of a low inner layer dielectric constant in our model. Results for the surface potential and distribution functions are presented for the case of anionic adsorption on the surface.