Facile synthesis of Aluminum-doped Bi₂WO₆ and enhanced remediation of aqueous Methylene Blue and Rhodamine B

Pristine Bi₂WO₆ and different concentrations of aluminum-doped Bi₂WO₆ nanoparticles were synthesized using a simple hydrothermal method for a comparative study of the decolorization of aqueous organic pollutants. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), UV–visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Brunauer–Emmett–Teller (BET), Zeta potential, field-emission scanning electron microscopy (FE-SEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS). The XRD pattern revealed the formation of an orthorhombic structure for pure and Al-doped Bi₂WO₆. Aluminum doping decreased the crystallite size. The formation of 3D flower-like nanostructures that were composed of 2D nanosheets was observed through FE-SEM. The band gap increased because of the doping aluminum, which revealed the blue shift of the band gap. We performed both photocatalytic and adsorption experiments for 20 ppm aqueous Methylene Blue (MB) and Rhodamine B (RhB) for all synthesized catalysts. The aluminum-doped Bi₂WO₆ catalysts showed enhanced decolorizing efficiency, and 0.15Al-Bi₂WO₆ exhibited the best performance for adsorption. The results were analyzed using various models such as second-order kinetics, the BMG model, and the intraparticle Weber and Morris diffusion model. We found taht 97.02% and 95.61% of MB and RhB dye solutions decolorized in 20 and 30 min using 0.15Al-Bi₂WO₆, with second-order rate constants of 0.566 Lmg^-1min^-1 and 0.225Lmg^-1min^-1, respectively.