Microwave heating can be applied to regeneration of an adsorbent in the removal of volatile organic compounds in very low concentration. In this study, binary adsorption of ethylene and water vapor on mordenites (MORs) was carried out for very low concentration of ethylene. Microwave was irradiated to the adsorbent bed and the effect of adsorbed water on the heating of MORs and the desorption of the adsorbates were investigated. In the binary adsorption, all MORs showed linear adsorption for ethylene in very low concentration range and the amounts of adsorbed ethylene decreased as compared with the adsorption of the single component. NaMOR was heated up rapidly and to high temperature by microwave irradiation under both dry and humid conditions as compared with HMORs. Due to the strong adsorption of water on NaMOR, the coexisting water vapor hindered the adsorption of ethylene, but promoted microwave heating. In microwave heating of NaMOR after pre-adsorption of ethylene and water, ethylene was concentrated maximally about nine times as high as that in initial feed. (C) 2005 Elsevier B.V. All rights reserved.