TiO2/ZSM-5 composites were prepared from SiO2 of rice husk ash and TiO2 sol from hydrolyzed TiOSO4 salt. The combined effect of these two materials greatly enhanced the photocatalytic decolorization of methylene blue dye solution. The instant decolorization of the dye solution in the dark by the composite, TiO2/ZSM-5 (wt ratio 1:1), resulted from the combination of the adsorption by ZSM-5 zeolite and TiO2 nano-particles, and of Na2SO4 salt adhering to the composite surface. As a strong flocculating agent, the SO42- ion caused the precipitation of the dye onto the composite surface which consequently enhanced the photocatalytic decolorization of the dye under UV irradiation. The composite, TiO2/ZSM-5 (wt ratio 1:5), completely decolorized the methylene blue dye in 2.5 h, giving an equivalent performance to that of TiO2, P-25 powder. (C) 2007 Elsevier B.V. All rights reserved.