Copper-containing magnetite supported on natural clay as a catalyst for heterogeneous photo-Fenton degradation of antibiotics in WWTP effluent

The use of natural clay as a support for magnetite and copper-containing magnetite was evaluated for heterogeneous Fenton/photo-Fenton degradation of trimethoprim and sulfamethoxazole. In Fenton experiments, the incorporation of copper ions on magnetite played an important role in the decomposition of hydrogen peroxide. Photo-Fenton experiments were performed under solar and UV-LED (370 nm) irradiation, with complete degradation of both antibiotics in purified water achieved under solar irradiation. Evaluation of the effects of inorganic anions and organic carbon showed that the highest •OH scavenging was due to CO32-/HCO3- and organic matter content. From a practical perspective, treatment of wastewater treatment plant effluent under solar irradiation resulted in 52% and 41% degradation of TMP and SMZ, respectively, together with 15% removal of dissolved organic carbon. The material maintained efficiency during 3 reuse cycles, showing its potential for use as a low-cost catalyst. The intermediates identified by UHPLC/MS indicated that TMP degradation involved hydroxylation, demethylation/hydroxylation, and cleavage pathways, while SMZ degradation involved hydroxylation, breaking of the sulfonamide bond, and opening of the isoxazole ring.