Enhanced refractory organics removal by ^•OH and ¹O₂ generated in an electro-oxidation system with cathodic...

Recently, carbon nanotubes coated carbon black and polytetrafluoroethylene (CNTs-C/PTFE) gas diffusion electrode was used as an air-cathode in an electro-oxidation (EO) system for effectively generating hydrogen peroxide (H₂O₂) through a 2-electron oxygen reduction reaction (ORR). This ORR-EO system not only lowered applied voltage and conserved energy, but the synergistic peroxone (O₃/H₂O₂) reaction could increase hydroxyl radicals (^•OH) generation for organics elimination. However, a significant proportion of H₂O₂ was left in the effluent of ORR-EO, which was a loss of resources and energy. In this study, a Fenton-like reaction for in-situ H₂O₂ decomposition to generate active oxidation species was inserted by introducing MnO₂ into the cathodic catalyst layer, and the sole MnO₂/CNTs-C/PTFE air-cathode could accomplish 90% of phenol degradation. When MnO₂/CNTs-C/PTFE air-cathode combined with Ti/NATO anode in an ORR-EO system, all anodic oxidation, Fenton-like reaction, and peroxone took place to successfully generate ^•OH and singlet oxygen (¹O₂). Over 95% of TOC in phenol and landfill leachate bio-effluent was effectively eliminated, with 20% energy savings compared to the ORR-EO with CNTs-C/PTFE air cathode.