Yttrium incorporated TiO2 supported ZSM-5 catalysts were prepared by a sol-gel method and an ion exchange process. The structural features of the photocatalysts were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and surface area (BET) measurements. XRD analysis supplied information about the crystalline sizes of TiO2 and Y2O3 nanoparticles. AFM and SEM images revealed obvious variations in the surface morphology of raw ZSM-5 after TiO2 and Y2O3 loading. The photocatalytic performances of the supported catalysts were evaluated for the clecolorization of methyl orange (MO) solution under UV irradiation. The results showed that yttrium incorporation enhanced the clecolorization rate percentage of MO. The effects of TiO2 content, yttrium ion content, catalyst amount, pH and initial MO concentration were examined as operational parameters. The photocatalytic reactions followed pseudo- H rst-order kinetics and discussed in terms of Langmuir-Hinshelwood model. The repeatability of photocatalytic activity was also tested. A plausible mechanism is proposed for the route of degradation. (c) 2008 Elsevier B.V. All rights reserved.