Enhancement of CuS/Fe3O4@MIL-100(Fe) ternary composite by co-catalyst CuS for photo-Fenton degradation of oxytetracycline hydrochloride

Abstract

The efficiency of Fenton-like catalysts was critically affected by the rapid transfer of Fe²⁺/Fe³⁺, a process that was essential for the formation of active free radicals by H₂O₂. Herein, we synthesized CuS/Fe₃O₄@MIL-100(Fe) (CFM) ternary composites using hydrothermal and in-situ growth methods to enhance the degradation of oxytetracycline hydrochloride (OTC-HCl) in a Fenton-like photocatalytic system. The incorporation of CuS as a co-catalyst into the double iron-based system significantly enhanced photocatalytic activity, achieving a 95.31 % degradation efficiency for OTC-HCl within 50 min under optimized conditions. The catalyst had good reusability, has 86.64 % degradation efficiency after five magnetic recovery cycles, and still showed good catalytic performance in the presence of five different concentrations of common anions. Further analysis using active species quenching and electron paramagnetic resonance (EPR) experiments revealed the role of oxygen-containing radicals in the process. Liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations provided OTC-HCl degradation pathways and intermediates. X-ray Photoelectron Spectroscopy (XPS) analysis indicated that CuS enhanced the performance of the bis-iron-based materials by improving the transfer efficiency of Fe²⁺/Fe³⁺ and Cu⁺/Cu²⁺ ions, which in turn accelerated the generation of reactive radicals from H₂O₂.