Hydrothermal Synthesis and Catalytic Evaluation of TiO2-Fe3O4 Hybrid Nanoparticles for AOP Applications

Advanced oxidation processes (AOPs) have emerged as technologies for the removal of pollutants in water systems due to their ability to generate hydroxyl radical (•OH). However, the catalytic behavior and synergistic interactions of hybrid nanomaterials in different AOPs remain insufficiently quantified. In this study, TiO2-Fe3O4 hybrid nanoparticles (HNPs) were synthesized through a hydrothermal method and evaluated in Fenton, photocatalysis, and photo-Fenton processes. Three formulations (TiO2 to Fe3O4 1:1, 1:0.5, and 1:0.25) were prepared to investigate the influence of content on catalytic activity by indirectly quantifying •OH generation through 7-hydroxycoumarin formation. Physicochemical, structural and magnetic characterization shows a possible formation of core–satellite like and Janus-like HNPs with superparamagnetic behavior. Among the evaluated catalysts, the HNP-0.25 formulation exhibited the highest catalytic activity under photo-Fenton conditions, achieving a •OH generation rate of 0.11052 µmol min−1 g−1 and a synergy index of 11.26, which indicates a cooperative interaction between photocatalytic and Fenton pathways. Furthermore, the optimized HNPs demonstrated high degradation efficiency toward pollutants, achieving 99% degradation of methylene blue (k = 0.1528 min−1) and 97% removal of ciprofloxacin (k = 0.0699 min−1) after 50 min under photo-Fenton conditions. These findings demonstrate that the composition and hybrid nature of TiO2-Fe3O4 nanoparticles play a critical role in promoting synergistic AOP interactions, enhancing •OH generation and pollutant degradation efficiency.