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.
Keywords: Hydrogen peroxide; Hydroxyl radicals; ORR-EO; Refractory organics; Singlet oxygen.
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