APPLICABILITY OF THE DUBININ RADUSHKEVICH EQUATION TO CO2 ADSORPTION ON ACTIVATED CARBONS

The Dubinin-Radushkevich equation (DR) is generally applied to the CO2 adsorption data on activated carbons in order to find their micropore volume and also their apparent surface area. This equation is an adaptation of the more general Dubinin-Astakhov equation (DA) with n = 2. The value of n in the DA equation decreases with the percentage of burn-off of the activated carbon, and therefore, the DR equation can be appropriately applied to a few activated carbons with low to medium burn-off. For activated carbons with medium to high burn-off, the application of the DR equation to the CO2 adsorption isotherm leads to wrong conclusions. In these cases the experimental data are better fitted by the DA equation with a value of n lower than 2, which makes the apparent surface area obtained by the DA equation greater than that obtained by the DR equation and similar or higher to that obtained with N2 at 77 K by applying the BET equation.