APPLICATION OF ALPHA-PLOTS AND N-PLOTS TO N-2 ADSORPTION-ISOTHERMS OF ACTIVATED CARBONS

The application of the n and alpha methods to two different groups of N2 adsorption isotherms of activated carbons has been studied. The chemical nature of the adsorbent and the adsorbate and the adsorbent-adsorbate interactions have been established as two different means of assessing the standard N2 adsorption isotherms of non-porous carbon. The application of both criteria to N2 adsorption isotherms of activated carbons gave deviations at low and high relative pressures; these deviations were not significant in the evaluation of the micropore volumes and non-microporous surface areas of the carbons. Alternatively, the comparison between micropore volumes obtained by applying the Dubinin-Raduskevich (DR) equation and those from the n and alpha plots showed different results relating to the pore-size distributions of the carbons. Some alpha plots showed two straight portions, that located at lower alpha values being the most appropriate for evaluating the micropore volumes. In general, alpha and n plots have been shown to be more useful than the DR equation for analysing the N2 adsorption isotherms of highly activated carbons.