Synthesis of La-doped Bi2WO6 to study on the removal of RhB wastewater under visible light

Bismuth tungstate photocatalysts were prepared by the hydrothermal synthesis method which is both simple and safe. La was doped at different molar ratios into Bi2WO6 samples. The photocatalytic activity of the as-prepared samples was then evaluated by removal of Rhodamine B (RhB) solution under visible light irradiation. Samples with high photocatalytic activity were characterized by various methods, such as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area, and ultraviolet visible (UV–vis) diffuse reflectance spectra (DRS). Compared with pure Bi2WO6, the La doping effectively improved the photocatalytic activity of Bi2WO6. 3%La/Bi2WO6 sample displayed superior photocatalytic efficiency with nearly 98.2% removal of RhB solution in 120 min of visible light irradiation. The results of characterization revealed that the specific surface area of Bi2WO6 photocatalyst was also increased after La doping. It indicated that La doping decreases the band gap and hinders the re-binding of e− and h+. Therefore, the La-doped Bi2WO6 samples have an absorption property in the visible light range and have a good morphology. The experimentally determined photocatalytic mechanism showed that h+ was the main active species. The photocatalytic degradation effects of photocatalyst amount, initial RhB concentration, and initial pH of the RhB solution were investigated in the 3%La/Bi2WO6 sample, which optimized the photocatalytic activity. In addition, a possible mechanism is proposed to explain the process of RhB solution removal.