Stable CuFeO/Kaolin-based catalytic particle electrode in 3D heterogeneous electro-Fenton system for orange G removal: Synthesis, performance and mechanism

Orange G is a kind of widely applied but environment-unfriendly dye. Three-dimensional heterogeneous electro-Fenton (3D/HEF), as a combination of three-dimensional electrochemical (3D/E) and heterogeneous electron-Fenton (HEF), having attracted more attentions. However, it is still insufficient in the investigation of coupling mechanism and preparation of highly stable catalytic particle electrodes. Herein, stable copper iron oxide/Kaolin catalytic particle electrodes were synthesized via a facile sol-gel method and applied in 3D/HEF for OG removal. A 40 %-CuFeO/Kaolin (450 °C, 2 h) catalytic particle electrode was optimized and a stable Fe-O-Al bond was found to form between CuFeO and Kaolin. Under optimal conditions, the removal of OG and TOC could reach 99.48 % and 58.13 % respectively within 60 min in neutral environment. From well-designed comparative experiments, various effects such as anodic oxidation, three-dimensional electrochemical oxidation were distinguished, indicating that an excellent synergism between 3D/E attributed to Kaolin and HEF due to CuFeO was the significant cause for the superiority of CuFeO/Kaolin-based 3D/HEF. Radical scavenging experiments verified both hydroxyl radical (•OH) and superoxide radical were generated with •OH dominated, which could efficiently degrade OG through such steps as desulfonation, decolorization, naphthalene opening, benzene opening. Besides, the CuFeO/Kaolin catalysts represented high stability with OG removal still maintaining 92.18 % after 8 cycles, low ion leaching and wide applicability to other dyes, manifesting a kind of fine catalytic particle electrode applied in 3D/HEF have been designed for dye removal and furthermore, providing a new idea for preparing composite catalytic particle electrode in 3D/HEF hybrid system.