Nd-doped MoO₃@SiO₂ nanocomposites for sustainable dye degradation of congo red and crystal violet: Insights into structural, optical, and catalytic properties

The environmental persistence of synthetic dyes, notably Congo Red (CR) and Crystal Violet (CV), necessitates effective remediation strategies. This study presents the synthesis of 3%, 6% and 9% neodymium-doped molybdenum trioxide nanoparticles (Nd-doped MoO₃@SiO₂) supported on a silica matrix via a solvent-mediated co-precipitation method. Comprehensive characterization was performed using XRD, Raman, TEM, UV–vis spectroscopy, PL, FTIR, FESEM with EDX, and XPS. XRD analysis confirmed the successful incorporation of Nd³⁺ ions into the MoO₃ lattice with orthorhombic crystal structure, while TEM images revealed uniform dispersion with an average size of approximately 50 nm. UV–vis spectroscopy showed a blueshift in the absorption edge, suggesting increases the charge carrier concentration. FTIR and Raman spectra identified characteristic vibrational modes, affirming the structural integrity of the composite. XPS analysis verified the oxidation states and elemental composition, confirming the presence of Nd³⁺ and Mo⁶⁺. Photocatalytic experiments demonstrated that the 6% Nd-doped MoO₃@SiO₂ composite achieved degradation efficiencies of 94.6% for CR and 83.8% for CV under solar irradiation within 90 min. Kinetic analysis revealed that the degradation process adhered to first-order kinetics, with intraparticle diffusion influencing adsorption behavior. Adsorption isotherm analysis revealed that the Temkin model best described the adsorption equilibrium, suggesting multilayer adsorption and a heterogeneous energy distribution on the catalyst surface. Reusability tests confirmed the catalyst's stability, exhibiting less than 5% efficiency loss over four cycles. The Nd-doped MoO₃@SiO₂ nanoparticles as effective and reusable photocatalysts for dye-contaminated wastewater treatment.