Recent advances and trends of heterogeneous electro-Fenton process for wastewater treatment-review

Electrochemical advanced oxidation processes (EAOPs) are effective and environmentally friendly for the treatment of refractory organic pollutants. Among EAOPs, heterogeneous electro-Fenton (EF) process with in-situ formation of hydrogen peroxide (H2O2) is an eco-friendly, cost-effective and easy-operable technology to generate hydroxyl radicals ((OH)-O-center dot) with high redox potential. The generation of (OH)-O-center dot is determined by the synergistic H2O2 formation and activation. The surface catalytic mechanisms for H2O2 activation in the heterogeneous EF process were discussed. Some required features such as heteroatom doping and oxygen groups for H2O2 formation via selective two-electron oxygen reduction reaction (ORR) with carbonaceous electrode are summarized. The solid Fenton catalysts and integrated functional cathodes that widely used in heterogeneous EF for wastewater treatment are grouped into few classes. And the brief discussion on catalytic activity and stability of materials over different experimental conditions are given. In addition, the application of heterogeneous EF process on the remediation of emerging contaminants is provided. The challenges and future prospects of the heterogeneous EF processes about catalytic fall-off and multi-step/complex techniques for water purification are emphasized. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

Electrochemical advanced oxidation processes (EAOPs), particularly the heterogeneous electro-Fenton (EF) process, with in-situ formation of hydrogen peroxide (H2O2), have shown great potential for the effective and environmentally friendly treatment of refractory organic pollutants. This article discusses the surface catalytic mechanisms for H2O2 activation in the heterogeneous EF process and summarizes the required features for H2O2 formation via selective oxygen reduction reaction (ORR) with carbonaceous electrodes. It also provides an overview of solid Fenton catalysts and integrated functional cathodes used in heterogeneous EF for wastewater treatment, along with a brief discussion on their catalytic activity and stability under different experimental conditions. Additionally, the application of heterogeneous EF process in the remediation of emerging contaminants is highlighted, while emphasizing the challenges and future prospects related to catalytic fall-off and multi-step/complex techniques for water purification.