Efficient removal of N-nitrosodimethylamine and triclosan by nFe@Fe3O4 nanocomposites: Enhanced generation of active hydrogen atoms

In this study, nFe and Fe 3 O 4 composites (nFe@Fe 3 O 4 ) were prepared for the efficient removal of N -nitrosodimethylamine (NDMA) and triclosan (TCS) in water. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that nFe@Fe 3 O 4 consisted of a core of Fe 3 O 4 surrounded by a layer of spherical nFe. nFe@Fe 3 O 4 exhibited significantly reduced agglomeration, looser structure, slower passivation, and enhanced stability compared to nFe. nFe@Fe 3 O 4 exhibited excellent performance in the removal of NDMA and TCS. Under optimal conditions, the nFe@Fe 3 O 4 system achieved 99.9% removal of both NDMA and TCS after 72 h, significantly outperforming the nFe system alone. It also resisted interference from different pH values and ionic conditions well. The results of product analysis and density functional theory (DFT) calculations revealed that the removal of NDMA in nFe@Fe 3 O 4 was attributed to the cleavage of N=O and N-N bonds. Removal of TCS resulted from chlorine removal and ether bond cleavage. The identification and verification experiments of active species showed that active hydrogen atoms (•H) in solution were responsible for the significant removal of NDMA and TCS. Catalytic hydrogenation was the primary mechanism of this reaction. The Fe(III)/Fe(II) cycle regenerated Fe(II) to slow passivation. Fe 3 O 4 improved the electron transfer and proton conductivity of nFe@Fe 3 O 4 , accelerating its corrosion and enhancing generation of •H. Additionally, nFe@Fe 3 O 4 maintained excellent removal performance under repeated use, stability testing, and real water condition.