Integrating UV Photo-Fenton Catalysis Processes with Crystalline Spinel NiFe₂O₄ Nanostructures for Sustainable Removal of Antibiotics from Aqueous Medium with Mechanistic, Kinetic, and Environmental Insights

The widespread use of antibiotics in aquatic environments poses significant ecological and public health risks due to their long-term presence, harmful effects, and their role in the evolution of antibiotic resistance. Nickel ferrite (NiFe₂O₄) nanoparticles were synthesized and used as heterogeneous catalysts in a UV-assisted photo-Fenton method to degrade sulfamethoxazole (SFX) and metronidazole (MTZ) from aqueous solutions. XRD, SEM-EDS, and FTIR investigations showed the presence of a crystalline spinel phase having an average crystallite size of 19.91 nm, a porous surface shape, and a homogenous distribution of Ni, Fe, and O. Degradation studies were conducted with antibiotic concentrations ranging from 10-50 ppm under varied Fe²⁺ (0.02-0.04 mM), H 2 O 2 (0.1-0.2 mM), catalyst dosages (0.002-0.006 g/L), and pH (3-5). Under optimal circumstances of pH 3-4, 0.004-0.006 g/L catalyst, and higher oxidant doses, both antibiotics were consistently degraded by more than 90% within 120 minutes. At 10 ppm, SFX and MTZ were degraded by 94.2% and 93.2%, respectively. The degradation followed apparent pseudo-first-order kinetics with observed rate constants (k obs ) of 2.4 × 10⁻² min⁻¹ for SFX and 2.2 × 10⁻² min⁻¹ for MTZ. This behavior is consistent with the Langmuir-Hinshelwood model, which simplifies to pseudo-first-order kinetics at low pollutant concentrations in heterogeneous photocatalytic systems. The calculated Electrical Energy per Order (EE/O) was approximately 4.0 × 10³ kWh/m³/order for SFX and 4.27 × 10³ kWh/m³/order for MTZ under optimized conditions. Mechanistic analysis suggested that hydroxyl radicals (•OH) are the dominant reactive species, generated through Fe²⁺/Fe³⁺ redox cycling and UV-assisted catalytic processes. The NiFe 2 O 4 -supported photo-Fenton system significantly outperformed the traditional and advanced oxidation processes at low catalyst loadings, demonstrating the potential of NiFe 2 O 4 nanoparticles as a sustainable and scalable approach for antibiotic degradation in wastewater.