Flow-through electro-Fenton using nanoconfined Fe-Mn bimetallic oxides: Ionization potential-dependent micropollutants degradation mechanism

Herein, we present a flow-through electro-Fenton system for highly efficient and selective degradation of organic contaminants. The essential to this design was a functional nanohybrid filter cathode consisting of an electroactive carbon nanotubes (CNT) filter functionalized with bimetallic Fe/Mn oxide nanoparticles under nanoconfinement. Results suggested that the nanoconfined Fe/Mn-in-CNT filter exhibited a much higher organic degradation kinetics (1.65 times) relative to its unconfinement counterpart (Fe/Mn-out-CNT). Singlet oxygen was the primary reactive oxygen species in the Fe/Mn-in-CNT-based system, in sharp contrast with the hydroxyl radical-mediated pathway in the Fe/Mn-out-CNT-based system. The efficacy was closely correlated with the ionization potential of target organic molecules, with preferentially oxidized organics with the electron-donating ability. Both experimental evidences and theoretical results collectively revealed the superior performance associated with the synergistic effects among Fe, Mn, CNT, and electric field in the nanoconfined system.

Automated summary

In this study, a flow-through electro-Fenton system was developed for efficient and selective degradation of organic contaminants. The key element of the system was a functional nanohybrid filter cathode made of carbon nanotubes (CNT) functionalized with Fe/Mn oxide nanoparticles under nanoconfinement. The results showed that the nanoconfined Fe/Mn-in-CNT filter had significantly higher organic degradation kinetics compared to the unconfinement counterpart. Singlet oxygen was the primary reactive oxygen species in the nanoconfined system, while the hydroxyl radical-mediated pathway was dominant in the unconfinement system. The superior performance of the nanoconfined system was attributed to the synergistic effects among Fe, Mn, CNT, and electric field, as revealed by experimental and theoretical analysis.