Determination of the adsorption volume and surface of carbon adsorbents with developed mesoporosity

The isotherms of excess adsorption of CH₄ (at<i>P</i>=0.001–160 MPa), SF₆ (at<i>P</i>=0.001–2.4 MPa), and C₆H₆ (at<i>P</i>=0.0001–0.1 MPa) on carbon adsorbents—microporous carbons CMS and FAS with developed mesoporosity and graphitized soot—were measured in the 298–408 K temperature region. Calculation of the isotherms of absolute adsorption of the total content of these substances requires knowledge of the adsorption volume, which was determined by different methods: by the Dubinin—Radushkevich equation; by the experimental isotherm of excess adsorption and the equation of absolute adsorption; by the method using the intersection of nonlinear isosteres of excess adsorption and isosteres of absolute adsorption; by the comparative plot of values of the excess C₆H₆ adsorption Γ_FAS—Γ_soor; by the method using the difference of molecular radii of adsorptives and the surface of the specific adsorbent; and by the calculation of the adsorption layer thickness using the FHH equation for mesoporous systems. The results of determination of the adsorption volume for microporous systems of these carbons agree well with each other and with the passport data for the adsorbents. Analysis of the results revealed the peculiarity of the sulfur hexafluoride adsorption related to the formation of associates on the surface of the carbon adsorbents.