Enhancing Cu-EDTA decomplexation in a discharge plasma system coupled with nanospace confined iron oxide: Insights into electron transfer and high-valent iron species

Decomplexation of heavy metal-organic complexes dominated by reactive oxygen species (ROS) oxidation had attracted extensive attention. Nanospace confinement is a novel strategy to enhance pollutant removal due to its regulation on ROS transformation and local accelerated dynamics. Herein, nano-confined Fe₂O₃ catalyst supported by carbon nanotubes (Fe₂O₃-in-CNTs) was synthesized, and it displayed obvious synergistic effects on decomplexation of Cu-EDTA complex in a non-thermal plasma (NTP) process. Cu-EDTA decomplexation efficiency reached 98.8% within 20 min in the NTP/Fe₂O₃-in-CNTs system, and the corresponding kinetic constant was 4.5 and 2.5 times as that in single NTP and unconfined systems, respectively. Based on experimental and theoretical results, nanospace confinement induced electron localization around Fe and C atoms and rearrangement of orbital electrons, favoring strongly oxidative Fe^Ⅳ formation and catalytic decomposition of H₂O₂ and O₃. Nanospace confinement made Cu-EDTA decomplexation process transform from radical pathway to non-radical pathway. Cu-EDTA decomplexation pathways in the NTP/Fe₂O₃-in-CNTs were proposed.