Enhanced visible-light photocatalytic degradation of organic dyes using highly crystalline MgFe₂O₄ nanoparticles synthesized by co-precipitation

Magnesium ferrite (MgFe₂O₄) nanoparticles were successfully synthesized via a controlled co-precipitation route to develop efficient and environmentally benign photocatalysts for wastewater treatment. X-ray diffraction analysis confirmed the formation of a highly crystalline pure cubic spinel phase with an average crystallite size of approximately 19 nm, while scanning electron microscopy revealed agglomerated quasi-spherical particles with mean diameters of 40–42 nm. FTIR spectra exhibited characteristic metal–oxygen stretching vibrations corresponding to tetrahedral and octahedral sites, further validating the spinel structure formation. UV–Vis diffuse reflectance data showed strong visible-light absorption with direct and indirect bandgap energies of 2.51 eV and 2.18 eV, respectively, accompanied by a low Urbach energy (0.137 eV), indicating minimal structural disorder. The measured zeta potential (−29.52 mV) suggested moderate-to-good colloidal stability. Under natural sunlight, MgFe₂O₄ demonstrated remarkable photocatalytic activity, achieving degradation efficiencies of 98.64% for methylene blue, 94.08% for Congo red, and 89.56% for Rose Bengal within 120 min, following pseudo-first- and second-order kinetics. The outstanding performance is attributed to efficient visible-light harvesting, reduced electron–hole recombination, and enhanced generation of reactive oxygen species, establishing MgFe₂O₄ nanoparticles as promising candidates for sustainable photocatalytic degradation of organic pollutants in wastewater systems.