In-situ slow production of Fe2+ to motivate electro-Fenton oxidation of bisphenol A in a flow through dual-anode reactor using current distribution strategy: Advantages, CFD and toxicity assessment

Abstract

In-situ slow production of iron catalysts can not only simplify process control and solve the problem of difficult reuse of the ex-situ dosing catalysts, but also avoid the •OH consumption reaction caused by the excessive catalysts. However, the relevant research is relatively lacking. In this study, a flow through dual-anode electro-Fenton (EF) reactor using simple current distribution strategy was designed for the first time, and Fe2+ could be in-situ slowly generated to cost-effectively motivate EF oxidation. Compared to the traditional in-situ production of Fe2+ in EF system with a single iron anode, in-situ slow production of Fe2+ in dual-anode EF system using current distribution was more cost-effective. In multi-electrode EF system, continuous flow through reactor showed significant advantages over the traditional flow by and batch reactor in terms of electron and mass transfer, back-mixing phenomenon and convection diffusion, as proved by LSV, EIS analysis and computational fluid dynamics (CFD) simulations, such as turbulent kinetic energy, velocity, pressure and fluid trace distribution. The optimum conditions were attained by response surface methodology (RSM), including applied current of 53.59 mA, pH of 3.27, current ratio of iron anode of 35.89% and flow rate of 11.52 mL/min. Fenton reaction only occurred at the reaction zone where the iron anode was located, including the homogeneous Fenton reaction between the dissolved Fe2+ and electrogenerated H2O2 and the heterogeneous Fenton reaction caused by the iron oxide adhered on the cathode surface. Besides, the toxicity evolution was analyzed using the Kirby-Bauer disk diffusion method. In summary, this work provided an innovative and simple idea for the simultaneous in-situ production of H2O2 and Fe2+ at the most favorable rate for Fenton reaction, respectively.