Magnetic field-enhanced activation of O2 by nano zero-valent iron for efficient treatment of copper-complexed wastewater

The pervasive threat of toxic and stable heavy metal-organic complexes to aquatic ecosystems necessitates efficient decomplexation strategies. In this study, we developed a magnetic field (MF)-enhanced nano zero-valent iron (nZVI) system that activated O 2 for the removal of Cu(II) and chemical oxygen demand (COD) from Cu-complexed wastewater (EDTA-Cu, citrate-Cu, tartrate-Cu). The introduction of MF significantly enhanced Cu-complex destruction and Cu 2+ immobilization, while reducing toxicity and improving biodegradability. Mechanistic studies revealed that nZVI would displace Cu from complexes, reducing free Cu 2+ to Cu 0 on its surface. The resultant Cu 0 , in synergy with Fe 2+ , activated O 2 to generate reactive oxygen species (ROS), which cleaved metal-organic bonds and oxidized organic ligands. MF amplified this process by enhancing paramagnetic O 2 accumulation at nZVI/Cu 0 sites, accelerating ROS production via the O 2 ⟶O 2 •− ⟶H 2 O 2 ⟶•OH pathway, thereby boosting Cu-organic decomplexation and COD removal. Catalyst characterization further revealed that MF promoted Cu 0 dispersion on nZVI, preventing cluster formation and optimizing electron utilization for O 2 activation. As demonstrated by our energy-cost efficiency analysis, the MF/nZVI/O 2 process achieved 1.375–1.785 g Cu /kWh for Cu-organic wastewater treatment, significantly outperforming many previously reported processes. This study introduces a novel MF-assisted nZVI system for efficient treatment of Cu-complexes, offering a promising cost-effective and sustainable solution for practical application.