Neodymium Doped Copper Ferrite Nanocomposites as an Effective Magnetic Catalyst for the Organic Dyes Decomposition

Neodymium-substituted copper ferrite nanoparticles with composition CuNdxFe2−xO4 (x = 0.00–0.11) were synthesized via the sol–gel autocombustion method and systematically analyzed for their structural, optical, and photocatalytic properties. X-ray diffraction combined with Rietveld refinement confirmed the formation of a dominant spinel ferrite phase with minor secondary phases, while Nd incorporation induced a reduction in crystallite size and an increase in lattice microstrain without disrupting the long-range spinel structure. Optical studies based on diffuse reflectance UV–Vis spectroscopy and Tauc analysis revealed direct allowed electronic transitions and a non-monotonic variation of the optical band gap (2.7–3.1 eV) as a function of Nd content, attributed to the combined effects of lattice distortion, defect states, and cation redistribution. Photocatalytic performance was evaluated through Congo Red degradation under light irradiation in the presence of H2O2. Nd substitution significantly enhanced photocatalytic activity, with CuNd0.09Fe1.91O4 showing the highest degradation efficiency (~96%), whereas the highest apparent rate constant (Langmuir–Hinshelwood model) was observed for CuNd0.05Fe1.95O4. The results demonstrate that controlled Nd substitution effectively tunes the structural and electronic properties of CuFe2O4, leading to improved photocatalytic performance and highlighting its potential for wastewater treatment applications.