DETERMINATION OF CARBON POROSITY FROM LOW-TEMPERATURE NITROGEN ADSORPTION DATA - A COMPARISON OF THE MOST FREQUENTLY USED METHODS

This paper compares the most frequently used procedures for carbon por osity determination, i.e. the Dubinin-Radushkevich, Dubinin-Izotova, t and alpha(s) plot, Horvath-Kawazoe (HK) and micropore analysis method s. The correlations between the obtained results are presented, and th e importance of the choice of reference material for t and/or alpha(s) plot construction is displayed. It is concluded that only the HK meth od predicts smaller pore sizes. Our results show also that nitric acid oxidation of carbon and desorption in a flow of He in the temperature range 493-573 K leads to considerable changes in its porosity. Howeve r, for carbon previously oxidized and desorbed at 573 K, a pore-blocki ng effect occurs which probably results from the production of anhydri des in the carbon micropores.