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

[Display omitted] •Magnetic chainmail catalyst Fe3O4@CNT with confinement effect was successfully prepared.•Fe3O4@CNT catalyst shows a high TL degradation efficiency in different water matrixes.•TL degradation includes both radical and non-radical pathways.•CNTs act as stable carbon layer to accelerate electron transfer in PDS activation. 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 (OH, SO4−, O2−) 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.