Enhanced Refractory Organics Removal by •Oh and 1o2 Generated in an Electro-Oxidation System with Cathodic Fenton-Like Reaction

Abstract

Recently, carbon nanotubes coated carbon black and polytetrafluoroethylene (CNTs-C/PTFE) gas diffusion electrode was adopted 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 reduced applied voltage and saved energy, but the synergistic peroxone (O3/H2O2) reaction could enhance hydroxyl radicals (•OH) generation for organics removal. However, a large amount H2O2 was leftover in the effluent of ORR-EO, which was a waste of resource and energy. In this study, Fenton-like reaction for in-situ H2O2 decomposition to generate active oxidation species was induced by introducing MnO2 into the cathodic catalyst layer, and the sole MnO2/CNTs-C/PTFE air-cathode could achieve 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 effect to effectively generate •OH and singlet oxygen (1O2). Over 95% of TOC in phenol and landfill leachate bio-effluent were effectively removed, with 20% energy-saving compared to the ORR-EO with CNTs-C/PTFE air cathode.

Keywords: ORR-EO, Hydrogen peroxide, refractory organics, hydroxyl radicals, Singlet oxygen