Description of gas adsorption isotherms on activated carbons with heterogeneous micropores using the Dubinin-Astakhov equation

Activated carbons with heterogeneous micropores were prepared from moso bamboo via KOH activation in this study. Due to a high degree of burn-off during KOH activation, the Dubinin-Astakhov (D-A) equation that contains an empirical parameter n was proposed to describe adsorption isotherms in terms of micropore filling, which could highlight the increased surface heterogeneity. The characteristic curves revealed that at low relative pressures the fraction of micropore filling was higher with decreasing n value. The adsorption isotherms of CO₂ on the activated carbons prepared in this work at 273K, 298K, and 313K were satisfactorily described by the D-A equation with a correlation coefficient r² higher than 0.999. The characteristic energy of adsorption of 4.08kJ/mol and a value of n of 1.0 demonstrated that the adsorption of CO₂ on the moso bamboo-derived activated carbons was in agreement with the characteristic curves of the D-A equation.