Photosensitized and photocatalyzed degradation of azo dye using Lnⁿ⁺- TiO₂sol in aqueous solution under visible light irradiation

Abstract

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 (Lnⁿ⁺-TiO₂) sol catalysts were prepared by a chemical method of coprecipitation–peptization. The microstructure and morphology of Lnⁿ⁺-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 Lnⁿ⁺+-TiO₂hydrosol reaction system was studied to determine photocatalytic activity of the crystallized Lnⁿ⁺-TiO₂sol catalysts. Both TiO₂and Lnⁿ⁺-TiO₂sol catalysts demonstrated higher photocatalytic reactivity than Deggusa P25 TO₂powder catalyst significantly. The experiments also confirmed that the modification of TiO₂with 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 Lnⁿ⁺-TiO₂sol catalysts had significant absorption to visible light. Since this hydrosol reaction system using the Lnⁿ⁺-TiO₂sol 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.