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) with high redox potential. The generation of •OH 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.