In this study, a hydrophobic magnetite coated with an alkyl chain or a phenyl group on the surface was prepared and used as an adsorbent to investigate the adsorption behavior of aromatic compounds having various values of log P(ow) (phenol 1.46, benzonitrile 1.56, nitrobenzene 1.86, benzene 2.13, toluene 2.73, chlorobenzene 2.84 and o-dichlorobenzene 3.38) onto hydrophobic magnetite. The hydrophobic magnetites were modified with stearic acid and phenyltrimethoxysilane, and the modification amounts were 9.84 x 10(-3) and 4.17 x 10(-2) mmol/g, respectively. The aromatic compounds used in this study were divided into 3 groups depending on the log P(ow): 1 < log P(ow) < 2, 2 < log P(ow) < 3 and 3 < log P(ow). The adsorption amounts of above each group on the magnetite at an initial concentration of 100 ppm were 3.62 x 10(-3) (nitrobenzene), 1.92 x 10(-2) (phenol), 1.13 x 10(-1) (chlorobenzene), 2.42 x 10(-1) (benzene), and 3.10 x 10(-1) mmol/g (dichlorobenzene), respectively. This indicates that the adsorption behaviors depend on the strength of hydrophobicity of aromatic compounds. The adsorption mechanism for 2 < log P(ow) < 3 and 3 < log P(ow) is hydrophobic interaction and that for 1 < log P(ow) < 2 is pi-electron interaction. The quantitative relationship between the amount of adsorbed compounds and modified functional groups and the fitting for adsorption isotherm models suggested that this adsorption might form a multi-layer adsorption in the most cases. (C) 2011 Elsevier B.V. All rights reserved.