Photoluminescence and Photocatalytic Degradation of Methylene Blue and Methyl Red using Pr³⁺ Doped CdS Nanoparticles

The reflux technique was used to synthesize praseodymium-doped cadmium sulfide nanoparticles (Pr³⁺: CdS) with different doping concentrations 0, 5, 7, 9 and 11 at %. According to X-ray diffraction the samples were crystalline and hexagonal phase. Agglomerations of nanoparticles were observed from scanning electron microscopy image. When excited at 423 nm transitions of ³P₁ → ³H₅, ³P₀ → ³H₅, ³P₀ → ³H₆, ³P₀ → ³F₂ are obtained from the photoluminescence studies. The position, sharpness, and intensity increased with increase in concentration. Commission internationale de l’eclairage diagram shows that Pr³⁺ doped CdS had a hue almost white light, indicating that it might be used for solid-state illumination. For degrading methylene blue and methyl red, it was found that catalyst dose of 5 mg/L, pH 9 and pH 11 shows the best degradation percentage which is 89 and 94% respectively. Pr³⁺ doping enhanced methyl red and methylene blue degradation by photocatalyst. The experimental data matched both the Langmuir–Hinshelwood (L–H) and pseudo-first-order kinetics models. At the same ideal experimental conditions, the pseudo-first-order provided a better fit than the Langmuir–Hinshelwood kinetic model. The research suggests that Pr³⁺ doped CdS may operate effectively as a photocatalyst to detoxify harmful colors from wastewater.