Photosensitized and photocatalyzed degradation of azo dye using Lnn+-TiO2 sol in aqueous solution under visible light irradiation

With attempts to improve the photocatalytic activity of titanium dioxide (TiO2) catalysts and also extend the light absorption towards the visible light region, three types of the lanthanide ion-modified titanium dioxide (Ln(n+)-TiO2) sol catalysts were prepared by a chemical method of coprecipitation-peptization. The microstructure and morphology of Ln(n+)-TiO2 sol samples were characterized by atom force microscope, particle size distribution, and X-ray diffraction measurements. The analytical results showed that these sol catalysts had better particles distribution and interfacial adsorption ability than the powder catalysts in suspension. The photocatalytic degradation of azo dye (X-3B) in Ln(n+)-TiO2 hydrosol reaction system was studied to determine photocatalytic activity of the crystallized Ln(n+)-TiO2 sol catalysts. Both TiO2 and Ln(n+)-TiO2 sol catalysts demonstrated higher photocatalytic reactivity than Deggusa P25 TO2 powder catalyst significantly. The experiments also confirmed that the modification of TiO2 with lanthanide ions doping can improve the efficiency of interfacial adsorption and photocatalytic reactivity with azo dye. The photocurrent response of catalysts under visible light irradiation showed that the Ln(n+)-TiO2 Sol catalysts had significant absorption to visible light. Since this hydrosol reaction system using the Ln(n+)-TiO2 sol catalyst has several advantages over most conventional powder reaction systems, it may provide a new approach for further development of photocatalytic reaction systems in the future. (c) 2004 Elsevier B.V. All rights reserved.