Adsorption layer of charged surfaces: An exact nearest-neighbor model for the linear lattice

The effects of finite ion size and polyion concentration on the adsorption isotherms are examined within the context of a one-dimensional lattice rest ricted to nearest-neighbor interactions. The nearest-neighbor interactions include that of the bound ion with adjacent lattice sites as well as with a neighbor bound ion. Both screened and unscreened Coulombic interactions ar e employed,as they are shown to exhibit different behaviors under high salt concentrations. For the screened interactions, previously adsorbed ions ar e released, whereas for the unscreened Coulombic interaction charge reversa l is observed for sufficiently separated lattice sites. The effect of polyi on concentration is to provide a "constant" degree of adsorption for added salt concentrations less than the concentration of counterions released by the polyion, The model is applied to experimental data on monovalent and di valent salts.