A comparative study about the influence of metal ions (Ce, La and V) doping on the solar-light-induced photodegradation toward rhodamine B

Abstract

Water contamination by the textile dye effluents has become a serious environmental issue, which are threatening to the human health and biological diversity. The TiO2 photocatalysis has been proven to be used to remove textile dyes in water. In order to improve its solar-light activity, three metal ions, including cerium (Ce), lanthanum (La) and vanadium (V), were selected as dopants to prepare metal ions doped TiO2 particles by sol–gel method. The synthesized particles were characterized by X-ray diffraction, field scanning electron microscopy, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. Through the physicochemical properties of the resulting metal ions doped TiO2 particles, we found that characteristics of dopants could strongly affect the crystalline phase and crystallite size, the optical absorption spectrum and the bandgap energy of the modified TiO2 catalysts, and consequently influence the photocatalytic ability. We investigated the link between dopant’s characteristics and photoactivity of the doped catalysts, and deduced that the existence of dopant in the modified catalysts is crucial. In the case of Ce or La doping, the dopants homogeneously dispersed on the surface of TiO2 particles as oxides and interacted with TiO2 particles via REOTi bond. Nevertheless, the V species successfully entered the TiO2 lattice and substituted for Ti4+ due to its similar ionic radius with Ti. The photocatalytic activities of Ce-, La-, or V-doped TiO2 photocatalysts were evaluated by the degradation of rhodamine B under simulated solar-light illumination. In our case, only the doping of Ce or V could drive efficient solar-light activity. The bandgap energy of 1.0%-Ce–TiO2 was narrowed to 2.70eV and the removal ratio for dye could raise up to 83% with a relatively high calcination temperature.