LIMITING LAW FOR ION ADSORPTION IN NARROW PLANAR PORES

The adsorption of simple electrolytes in narrow planar pores is studied. The validity of the limiting law according to which the density of a classical ionic fluid approaches the fugacity in the pores barely exceeding the diameter of the ions is confirmed using the graphical expansion of the singlet-ion distribution. The same result emerges from the Kirkwood equation for the ion-wall correlation. The analysis is paralleled by the open-ensemble Monte Carlo simulation of the electrolyte in the pore, the periodic boundary conditions being implemented using the two-dimensional Ewald summation. The computations conform with theoretical predictions for extremely narrow slits and provide useful insights into the partitioning of the salt between the slit and the bulk solution at intermediate widths of the pores.