This investigation examined the instantaneous adsorption of NOx by moisture-saturated zeolites at ambient temperature. Among the zeolites studied, Faujasite exhibited the highest adsorption capacity owing to its relatively large pore size. Besides, the influence of cation was demonstrated by comparing the adsorption of zeolites with different cation densities (NaX vs. NaY, mesoporous silica MCM-48-like vs. Faujasite) and treatments (ion exchange of NaY with Cu2+). For the adsorption of NO, the effects of gas flow rates and pre-adsorbed hydrocarbons such as benzene, acetaldehyde or 1,3-butadiene were evaluated. It was proven that zeolite could efficiently capture nitrogen oxides in gas stream even it had been saturated by moisture, which will be valuable for the protection of environment and public health. (C) 2008 Elsevier B.V. All rights reserved.