Fe₃O₄@CNT as a high-effective and steady chainmail catalyst for tetracycline degradation with peroxydisulfate activation: Performance and mechanism

Confining metal oxide nanoparticles (NPs) in carriers such as carbon nanotubes (CNTs) has become a novel strategy for designing highly efficient and stable non-noble metal chainmail catalysts. In this study, Fe₃O₄ NPs were confined in the chainmail of multi-walled CNTs to prepare Fe₃O₄@CNT magnetic nanocomposite with confinement effect, and peroxydisulfate (PDS) was activated to degrade tetracycline (TL) in aqueous solution. Under the conditions of 20 °C, pH₀ = 7, 0.5 mM PDS and 0.4 g/L Fe₃O₄@CNT, TL degradation efficiency of 98.1% could be achieved by radicals (^[rad]OH, SO₄^[rad]−, O₂^[rad]−) and non-radicals (¹O₂) generated in the system. Stable carbon-layer structure can protect Fe₃O₄ NPs inside the chainmail from the influence of reaction environment. TL degradation efficiency still reached 80.2% after five cycles, and the leaching of Fe ions was less than 10 μg/L during each cycle. Electrochemical analysis and density functional theory (DFT) calculations show that electron transfer from active Fe₃O₄ NPs to the carbon layer to motivate the catalytic activity of carbon surface. This work will provide an innovative path for the application of chainmail catalysts in nano-water environmental remediation.