Surface bond-conjugated TiO2/SiO2 was prepared by means of the impregnation method. Based on the results of XRD, FTIR, XPS and BET measurements, the growth of titania (predominantly anatase) on the silica substrate seems to occur by anchoring of the TiO2 phase through Ti-O-Si cross-linking bonds. The structure model of TiO2/SiO2 was proposed. Compared to B-TiO2, the most efficient catalyst is 30 wt.% TiO2/SiO2 (Ims30), which showed three times higher photoactivity for the degradation of reactive 15 (R15). In addition, the catalyst had a higher photoactivity on a silica of smaller particle size than on the silica of larger particles. Silica gel plays the basic role of dispersion and support for power TiO2. The isoelectric point of the catalyst was 3.0 pH units by the measurement of zeta-potential, indicating the presence of the surface acidity of the: catalyst. The photodegradation and the adsorption of R15 and cationic blue X-GRL (CBX) were investigated with the change of initial aqueous pH. (C) 2001 Elsevier Science B.V. All rights reserved.