Iron-based resin heterogeneous photo-self-Fenton system for efficient photocatalytic degradation of antibiotic wastewater

The homogeneous Fenton reaction is limited by its pH requirements for the addition of the iron source and by the safety risks of working with high concentrations of hydrogen peroxide (H2O2) - both of which are major obstacles in the path toward utilizing this reaction for practical applications. In this study, we present a novel heterogeneous photo-self-Fenton system of iron-doped resorcinol formaldehyde (FRF) resin. This system is able to generate and utilize H2O2 in-suit, making it highly efficient at degrading and mineralizing various types of antibiotics (macrolides, sulfonamides, tetracyclines, quinolones) at a neutral pH without the need for additional reagents. Remarkably, the degradation rate constant of oxytetracycline (OTC) increased by 34.2 times compared to the resorcinol formaldehyde (RF) photocatalysis. The enhanced degradation performance of this system is attributed to (i) The Iron-anchored RF, which facilitates the rapid transfer of photogenerated electrons, thereby accelerating the recycling of iron ions and improving the migration and separation efficiency of photogenerated carriers. (ii) The heterogeneous photo-self-Fenton reaction using in situ generated H2O2 to produce abundant hydroxyl radicals. Finally, the mechanism of action and the mineralization pathway of OTC were systematically studied. The OTC undergoes demethylation, hydroxylation, and ring-opening and ultimately is completely mineralized to CO2 and H2O. The work provides a new sustainable pathway for extensively constructing heterogeneous photo-self-Fenton systems.