Degradation of pharmaceutical contaminants in water using iron-based spinel ferrites in a heterogeneous photo-Fenton process

Abstract: Pharmaceutical contaminants are increasingly detected in aquatic environments due to their widespread use, incomplete removal in conventional wastewater treatment plants, and continuous discharge into natural water bodies. Even at trace concentrations, these compounds may disrupt ecosystem balance, highlighting the need for effective remediation technologies. Advanced oxidation processes, particularly the heterogeneous photo-Fenton process, have emerged as promising alternatives for the degradation of persistent pharmaceutical contaminants. In this study, iron-based spinel ferrites of cobalt, manganese, and copper (CoFe2O4, MnFe2O4, and CuFe2O4) were synthesized by coprecipitation. The materials were structurally, morphologically, and optically characterized. In addition, ferrite nanoparticles supported on graphene oxide were prepared to extend the evaluation to supported catalytic systems and different pharmaceutical compounds. Powder X-ray diffraction (PXRD) confirmed the formation of spinel ferrite phases. Field emission scanning electron microscopy (FE-SEM) revealed quasi-spherical agglomerated morphologies, while X-ray photoelectron spectroscopy (XPS) confirmed the presence and expected oxidation states of the constituent elements at the material surfaces. Diffuse reflectance spectroscopy (DRS) was used to estimate optical band gap values through the Tauc method, yielding values in agreement with those reported for spinel ferrite photocatalysts. The catalytic activity of the ferrites toward the degradation of pharmaceutical contaminants was evaluated under UV irradiation using the heterogeneous photo-Fenton process. Degradation strongly depended on ferrite composition, with CuFe2O4 showing the highest activity during the degradation of sulfamethoxazole, used as a model pharmaceutical compound, and achieving over 95% degradation after four consecutive reuse cycles. Kinetic analysis indicated apparent pseudo-first-order behavior, with higher rate constants for CuFe2O4 compared to CoFe2O4 and MnFe2O4. Scavenger experiments confirmed the dominant role of hydroxyl radicals, while degradation product analysis revealed the formation of short-chain carboxylic acids, indicating progressive oxidation of the pharmaceutical molecules. Preliminary experiments using real water matrices demonstrated the potential applicability of the catalytic system under more complex conditions.