Commentary on the paper ‘ ‘ On the adsorption affinity coefficient of carbon dioxide in microporous carbons ’ ’ by E . S . Bickford et al . ( Carbon 2004 ; 42 : 1867 – 71 )

The recent letter to the editor by Bickford et al. [1] discusses the uses of the CO2 affinity coefficient in microporous carbons, bCO2 , and its physical significance. The paper points out the lack of having absolute b values and attempts to give answer to the question of the suitability of the value of bCO2 = 0.35 in microporous carbons. The authors conclude that this cannot be considered a ‘‘classical’’ value and that much more work is needed to clarify its physical significance, in order to maintain the well-deserved popularity of the Dubinin– Radushkevich equation. We welcome the effort of the authors to address – and even challenge – the use of bCO2 to characterize microporous carbons. However, we cannot agree with their conclusions. Firstly, because we feel that the importance and relevance of b has been overestimated in the paper. Secondly, because, on the basis our own research, a suitable classical value of bCO2 near 0.35 appears to exist. Thus, we have reported excellent agreements on the characteristic curves of different carbons, obtained with many couples comparing CO2 and benzene and or N2 adsorption. In all the cases, values near 0.35 for CO2 and 0.33 for N2 have been used. We wish to address the following three issues.