CoFe2S4-modified CNTs catalyst to activate peroxymonosulfate under a wide range pH for high-efficient tetracycline degradation via radical and non-radical paths

Abstract

Developing resilient and stable carbon-based metal catalysts for activating peroxymonosulfate (PMS) has attracted great attention in the advanced oxidation processes (AOP) area for removing organic pollutants in wastewater. This study synthesized CoFe₂S₄/CNTs (CFS-CNTs) nanocomposites using hydrothermal technique, which can activate PMS for efficient degradation of tetracycline (TC). A detailed characterization of the synthesized catalysts was conducted, and their catalytic performance was assessed by varying parameters such as catalyst dosage, PMS concentration, pH, and the presence of co-existing substances. The results demonstrated that CFS-CNTs showed excellent TC removal efficiency and reusability, even showing satisfactory degrading performance for various surface water matrices. The superior activities of the prepared catalysts are attributed mainly to the synergistic interaction of the bimetallic sulfides and CNTs. This synergy aids in the uniform dispersion of the catalysts and increases the availability of catalytic sites, which are essential in producing more active species. Free radical quenching experiments, chemical probe analyses, and electron paramagnetic resonance (EPR) demonstrated that SO₄·⁻ and ¹O₂ were the primary reactive oxygen species generated during the reaction environment. X-ray photoelectron spectroscopy (XPS) and electrochemical assessments also indicate that carbon nanotubes also functioned as high-speed charges, facilitating channels to achieve rapid electron transfer and accelerating the cycling of metal valence states. The TC degradation pathways, intermediate toxicity assessment, and CFS-CNTs/PMS system response mechanisms were also proposed. These findings provide new insights into the application of metal sulfides in PMS systems for the treatment of wastewater containing refractory organic pollutants.