Nonionic organic contaminants (NOCs) such as benzene, toluene, and phenol from contaminated wastewater can be effectively adsorbed by organo-zeolites. Organo-zeolites were prepared from synthetic ZSM-5 and natural zeolites, by exchanging the quaternary amines, i.e. hexadecyltrimethylammonium (HDTMA) bromide and n-cetylpyridinium bromide (CPB). The maximum adsorption of CPB onto these zeolites is in the order of clinoptilolite >ZSM-5-88 (SiO2/Al2O3 = 88) > ZSM-5-31 (SiO2/Al2O3 = 3 1) which is mainly dependent on the external cation exchange capacity (ECEC) of each zeolite. Batch adsorption experiment was carried out to remove benzene, toluene, and phenol from aqueous solution using the above-mentioned organo-zeolites. In addition, as-synthesized MCM-41 molecular sieve was employed for removal of organic contaminants from aqueous solution. The experimental results were fitted to the Langmuir, Freundlich, Redlich-Peterson and linear equation isotherms to obtain the characteristic parameters of each model. Our resultant data showed that nonlinear form of Langmuir, the Freundlich and Redlich-Peterson could be fitted well with sorption data in most cases. According to the evaluation using the Langmuir equation, the maximum organics adsorption by synthesized MCM-41 was much greater than that of the natural clinoptilolite and ZSM-5 zeolites. (C) 2004 Elsevier B.V. All rights reserved.