Adsorption of electrolyte in a templated hard-sphere matrix. Predictions of the continuum replica Ornstein–Zernike approach

Abstract

Thermodynamic and structural properties of the primitive model of size asymmetric 1-1 electrolyte solutions in a disordered hard-sphere matrix environment mimicking a microporous adsorbent were studied. The influence of the hard-sphere template on the adsorption properties of the material was analyzed. The numerical results of our study follow from the application of the replica Ornstein–Zernike integral equations, complemented by the hypernetted chain closure. Two different electrolyte models were examined with parameters mimicking lithium and sodium chloride solutions. The excess chemical potential for adsorbed electrolyte in an untemplated and a templated hard-sphere matrix was studied. Steric effects due to matrix confinement are known to have substantial influence on the properties of the annealed electrolyte. Our results showed the hard-sphere template produces a distribution of obstacles which increases the adsorption of electrolyte compared to the untemplated matrix case. The results were explained with regard to the pair-distribution functions for the various interaction pairs.