The present work was focused on photocatalytic oxidation of the model molecule reactive brilliant X-3B by lanthanide-modified TiO2 samples under artificial solar and UV irradiation. Experimental results showed that the TiO2 samples doping with lanthanide (Ce and Gd) could greatly enhance the activity of pure TiO2, and could extend the absorption range to visible region. The optimum doping amount was 0.2 and 0.5 at.% for Ce- and Gd-doped TiO2 particles, respectively. The degradation kinetics of X-3B on Ce-doped TiO2, Gd-doped TiO2, and pure TiO2 were studied as well. The results exhibited that the degradation of X-3B on all the samples were in accordance with the first-order model. The trend of apparent reaction rate constants k(app) was as follows, Gd-doped TiO2 > Ce-doped TiO2 > pure TiO2, under solar illumination. Scatchard plot analysis was used to evaluate the adsorption phenomena of as-prepared samples, and it indicated that lanthanide doping can improve the efficiency of interfacial adsorption of TiO2 samples. The trend was the same as that of photocatalytic activity. (C) 2008 Elsevier B.V. All rights reserved.