The adsorption of polyethyleneglycol-400 (PEG-400) on zeolites NaA, CaA, NaX and NaY have been investigated by using FT-IR spectroscopy and scanning electron microscopic (SEM) analyses. The spectral data have indicated that the source of adsorption of the PEG-400 on the mentioned zeolites is the interaction between the (OH) group of the liquid adsorbent and the surface silanol groups of the zeolites by means of a hydrogen bond. Shortly, the PEG binds with the silanol groups through the hydrogen bonding where the ethereal oxygen acts as a hydrogen bond accepter. A part of the PEG molecule remains adsorbed on the surface and the rest part remains protruded. So, the most of the silanol groups on the zeolites are masked by the PEG-400. (C) 2009 Elsevier B.V. All rights reserved.