MOLECULAR-SIEVE BEHAVIOR OF ACTIVATED CARBONS

Analysis of data for the adsorption of various molecular probe molecul es on a number of different microporous carbons has revealed an empiri cal relationship between log(n(0)) and log(V-m), where n(0)/mmol g(-1) is the micropore capacity for a given adsorptive and V-m/cm(3) mol(-1 ) the corresponding adsorptive molar volume. It is shown that observed differences in the linearity and slope of the log(n(0)) vs log(V-m) p lots can be rationalised on the basis of different types of molecular sieve behaviour and that analysis of the plots should therefore be abl e to provide useful information relating not only to the micropores th emselves but also to the micropore entrances. It is also concluded tha t the adsorption of nitrogen is atypical while, with regard to water v apour adsorption, the results indicate that adsorption only occurs in pores of slit-width greater than or equal to 0.37 nm (rather than the previously suggested value of greater than or equal to 0.5 nm), due to the fact that a stable hydrogen-bonded structure is not able to form in narrower ports.