ASSESSMENT OF THE SURFACE-AREA AND MICROPOROSITY OF ACTIVATED CHARCOALS FROM IMMERSION CALORIMETRY AND NITROGEN ADSORPTION DATA

For two sets of activated charcoals (one activated in water vapor, the other in phosphoric acid) the surface area available to a given organic molecule is determined by comparing the enthalpy of immersion with that of a nonporous reference sample. Examination of the theoretical adsorption potentials in cylindrical or slit-shaped micropores suggests that the above surface area is closer to reality than the Brunauer-Emmett-Teller equivalent area. Following these lines, a micropore size distribution is directly derived from the enthalpies of immersion in liquids of different molecular sizes. They compare reasonably well with results obtained from the analysis of adsorption isotherms and enthalpies of nitrogen adsorption.