In this paper, a dual chelating sol-gel method was used to synthesize BaTiO3 nanoparticles by using acetylacetone and citric acid as chelating agents. The samples calcined at different temperatures were analyzed by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscope (SEM) and UV-vis diffuse reflectance spectra (UV-vis). The results indicated that cubic phase BaTiO3 nanoparticles about 19.6 nm can be obtained at 600 degrees C and changed into tetragonal phase at 900 degrees C about 97.1 nm. All the BaTiO3 nanoparticles showed effective photocatalytic activities on the removal of humic acid (HA) under UV light irradiation. A comparison of single (acetylacetone or citric acid) and dual chelating (acetylacetone and citric acid) synthetic processes was also studied and the results demonstrated that the dual chelating agents indeed reduced phase transformation temperature from cubic to tetragonal BaTiO3. (C) 2012 Elsevier Ltd. All rights reserved.