CeO2-TiO2 nanoparticles were prepared by the sol-gel process using 2-hydroxylethylammonium formate as room-temperature ionic liquid and calcined at different temperatures (500-700 degrees C). CeO2-TiO2-graphene nanocomposites were prepared by hydrothermal reaction of graphene oxide with CeO2-TiO2 nanoparticles in aqueous solution of ethanol. The photocatalysts were characterized by X-ray diffraction. BET surface area, diffuse reflectance spectroscopy. scanning electron microscopy, and Fourier transformed infrared techniques. The results demonstrate that the room-temperature ionic liquid inhibits the anatase-rutile phase transformation. This effect was promoted by addition of CeO2 to TiO2. The addition of graphene to CeO2-TiO2 nanoparticles enhances electron transport and therefore impedes the charge recombination of excited TiO2. The photodegradation results of the pollutants in aqueous medium under UV irradiation revealed that CeO2-TiO2-graphene nanocomposites exhibit much higher photocatalytic activity than CeO2-TiO2 and pure TiO2. The photocatalytic activity of CeO2-TiO2-graphene nanocomposites decreases with additional increasing of the graphene content. Moreover, comparison of the photocatalytic activities of CeO2-TiO2-graphene with the other CeO2-TiO2-carbon demonstrates that CeO2-TiO2-graphene nanocomposites have the highest photocatalytic activity due to their unique structure and electronic properties. Chemical oxygen demand for solutions of the pollutants gave a good idea about mineralization of them. (C) 2011 Elsevier B.V. All rights reserved.