Fe-MOFs/CuS nanocomposite-mediated peroxymonosulfate activation for tetracycline degradation: Boosted dual redox cycles

Engineering dual redox centers in catalysts for peroxymonosulfate (PMS) activation emerges an efficient strategy to achieve high pollutant degradation performance. In this study, MIL-88 A (Fe) supported copper sulphide (MIL-88 A (Fe)@CuS) was developed as a PMS activator to degrade aqueous tetracycline (TC). MIL-88 A (Fe)@CuS showed high catalytic performance towards PMS activation, and a TC degradation rate of 91.0 % (20 mg/L) could be achieved within 40 min, with a k value of 0.3921min⁻¹. The TC removal rate of the MIL-88 A (Fe)@CuS system was 1.55 and 1.12 times higher than that of MIL-88 A (Fe) + PMS and CuS + PMS systems, respectively. MIL-88 A (Fe)@CuS also possessed excellent stability in terms of good activity maintenance, low metal leaching, and stable structure. In addition, the MIL-88 A (Fe)@CuS + PMS system exhibited good degradation performance towards different antibiotics in real water metrics. In TC degradation, reactive oxygen species (ROS) include SO₄^•-, •OH, O₂^•- and ¹O₂ are involved, and SO₄^•- served as the main species. The synergistic effect of both Cu and Fe cycles for PMS activation was confirmed, and S benefited the rapid Cu²⁺/Cu⁺ and Fe³⁺/Fe²⁺ cycling. Furthermore, three potential TC degradation pathways have been identified based on experimental and computational studies. Overall, this work presents a feasible approach for developing efficient composite catalysts for advanced oxidation processes with dual redox cycles.