Mass transfer of ozone in aqueous phase is a major aspect of ozonation and advanced oxidation processes. The aim of this study is to compare the performances of an ejector with those of a more traditional gas/liquid contactor: a bubble column. The hydrodynamic study showed that the volumetric mass transfer coefficient of the ejector (K(L)a = 7.2 x 10(-2) to 1.35x 10(-1) s(-1)) was greater than that of the bubble column's (K-L,a = 1.5 x 10(-2) to 2.8 x 10(-2)S(-1)). Very important differences in the values of the residence time and gas retention rate were also observed. A study of phenol degradation was performed. Due to its specifications the ejector is very efficient when the kinetics of reaction is fast (diffusion-controlled regime). In both semi-batch and open circuits, the phenol was quickly eliminated and the ozone transfer was very high (up to 98%). It is to be noted that these results were obtained for a processing time of approximately I s. (C) 2007 Elsevier B.V. All rights reserved.