Efficient Photocatalytic degradation of direct blue 15 dye using samarium doped bismuth tungstate nanosheets: A sustainable approach towards wastewater treatment

The rare earth metal, samarium (Sm³⁺) doped bismuth tungstate (Bi₂WO₆) nanoparticles were prepared by a one-pot hydrothermal method. The powder X-ray diffraction (XRD) analysis confirmed the formation of Bi₂WO₆ with an orthorhombic crystal structure. The crystallite size of Bi₂WO₆ decreased from 20.73 to 9.25 nm as the Sm substitution in the W lattice increased. The vibrational modes of W–O, Bi–O, and Sm–O were identified in the range of 500–900 cm⁻¹. The optical bandgap of Sm³⁺ doped Bi₂WO₆ nanoparticles increased from 2.86 to 2.95 eV with higher Sm doping levels. The surface morphology revealed the formation of flower-like sheets in the Sm³⁺ doped bismuth tungstate. The energy dispersive X-ray (EDX) spectrum of Sm³⁺ doped Bi₂WO₆ nanoparticles confirmed the presence of Sm, Bi, W, and O without any other impurities. The small peak detected at 1082.14 eV in the survey scan of Sm³⁺ doped Bi₂WO₆ nanoparticles belonged to Sm3d. In the photocatalytic degradation of direct blue 15 (DB15) under visible light irradiation, the efficiency of the nanoparticles increased with higher Sm³⁺ concentration. The obtained results demonstrated that the Sm–Bi₂WO₆ nanosheets could provide an effective and sustainable solution for treating the wastewater containing direct blue 15 dye.