The reactive adsorption of NO2 over activated carbon (AC) was investigated at 50 degrees C. Both the NO2 adsorption and its reduction to NO were observed during the exposure of AC to NO2. Temperature programmed desorption (TPD) was then performed to evaluate the nature and thermal stability of the adsorbed species. Adsorption and desorption processes have been proposed based on the nitrogen and oxygen balance data. The micropores in AC act as a nano-reactor for the formation of -C(ONO2) complexes, which is composed by NO2 adsorption on existing -C(O) complexes and the disproportionation of adsorbed NO2. The generated -C (ONO2) complexes are decomposed to NO and NO2 in the desorption step. The remaining oxygen complexes can be desorbed as CO and CO2 to recover the adsorptive and reductive capacity of AC. (C) 2010 Elsevier B.V. All rights reserved.