USE OF N-2 AR AND CO2 ADSORPTION FOR THE DETERMINATION OF MICROPOROSITY AND SURFACE FRACTAL DIMENSION OF CARBON-BLACKS AND SILICAS

The microporosity of silicas and carbon blacks is characterized by using the Dubinin-Radushkevitch (D-R) equation. It is shown that the shape of the D-R lines corresponding to the adsorption of N2 and Ar on silicas are very different from that obtained on carbon blacks. It is explained by differences in the accessibility of the micropores for small molecules at low temperature. The Ar and N2 BET surface areas are determined and the value of the molecular area of N2 on silicas is discussed. The surface fractal dimensions of the two types of adsorbents are determined by means of the FHH fractal equation from the N2 adsorption isotherm above the monolayer coverage.