Hydroxyl Radical Generation in Heterogeneous Fenton Reaction and Its Interaction with Nanoplastics as Potential Advanced Oxidation Process

Growing concern over nanoplastics as emerging pollutants calls for effective treatment methods, with advanced oxidation processes (AOPs) showing strong potential for their degradation. This study examines the interaction between polyethylene terephthalate nanoplastics (PET-NPs) and magnetite nanoparticles (MNPs) in a heterogeneous Fenton-like system, focusing on colloidal behavior, hydroxyl radicals (●OH) generation, and potential degradation pathways. Zeta potential (ZP) and particle diameter measurements were used to characterize nanoparticle dispersion and aggregation mechanisms over a pH range of 3–9.5. The results revealed a pronounced pH-dependent stability, with MNPs exhibiting larger hydrodynamic diameters (283 nm) and lower stability at pH 3 (ZP: −9.8 mV) compared with neutral or alkaline conditions (189 nm; ZP: −44 to −42 mV). PET-NPs exhibited minimal agglomeration at a pH of 9.5 (ZP: −25.6 mV). Unlike conventional Fenton systems, ●OH production peaked at pH 7–9.5 (0.3–0.35 μM), attributed to preserved Fe2+ sites and reduced particle agglomeration. Although PET-NPs resisted oxidative degradation, their aggregation with MNPs enabled magnetic recovery (46% efficiency at pH 3) through charge screening, Fe3+/Fe2+ bridging, and hydrophobic interactions. These findings highlight MNPs’ potential for sustainable nanoplastic separation and emphasize the need for optimized catalysts to enhance ●OH-driven degradation. Overall, this work advances understanding of nanoplastic–magnetite interactions and offers insights into AOP applications.