A pH self-regulated three-dimensional electro-Fenton system with a bifunctional Fe-Cu-C particle electrode: High degradation performance, wide working pH and good anti-scaling ability

Three-dimensional electro-Fenton system (3DEF) shows great prospect for wastewater treatment. However, the development of an efficient particle electrode with wide working pH and good anti-scaling ability still remains a challenge. In this study, a novel iron-copper-carbon black (Fe-Cu-C) composite was fabricated through a one-step process of pyrolyzing the metal-resin precursors and worked as the particle electrode in the three-dimensional electro-Fenton reactor. In this system with electrodes polarization, the anode-to-cathode flow mode created a locally acidic zone in the packed bed with Fe-Cu-C particle, which facilitated the H2O2 generation from 2-electron reduction of O2 and decomposition into center dot OH via heterogeneous Fenton reaction. Consequently, it was found that average p-Nitrophenol (p-NP) removal efficiency of 88% and average COD removal efficiency of over 76% were achieved even after 6 h continuous treatment in the continuous-flow 3DEF system packed with Fe-Cu-C particles at a current density of 20 mA cm-2 and flow rate of 1.33 mL min- 1. Noticeably, the flow-through 3DEF had the appreciable anti-scaling ability to resist the deactivation of particle electrodes induced by hardness ions and showed little sensitivity to solution pH in the range of 4.0-10.0 with specific energy consumption of approximately 0.089 kW h g-1 COD. Generally, this material could be used as a low-cost particle electrode in combination with flow-through 3DEF for practical wastewater treatment.