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

• Activated carbons with heterogeneous micropores were prepared via KOH activation.
• The adsorption of CO2 on the activated carbons obeys the Dubinin–Astakho equation.
• Carbon surface heterogeneity is described by the Dubinin–Astakho parameter n.
• The value of n for CO2 adsorption is smaller than that reported in the literature.
• The activated carbons prepared in this work had highly heterogeneous micropores.

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 273 K, 298 K, and 313 K were satisfactorily described by the D-A equation with a correlation coefficient r2 higher than 0.999. The characteristic energy of adsorption of 4.08 kJ/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.