A dual-cathode pulsed current electro-Fenton system: Improvement for H₂O₂ accumulation and Fe³⁺ reduction

In conventional electro-Fenton (EF), high H₂O₂ accumulation and Fe³⁺ reduction rate are difficult to synchronously achieve on a single cathode. Then a dual-cathode pulsed current EF (DCP-EF) is proposed, where different current density imposes on gas diffusion cathode (GDE) and carbon felt (CF) alternately. In this system, GDE is mainly for H₂O₂ accumulation, while CF is primarily for Fe³⁺ reduction. Optimal current density on GDE for H₂O₂ formation is 10 mA cm⁻², while it is 2.5 mA cm⁻² for Fe³⁺ reduction on CF. A switching time of 20 s is alternatively utilized on each cathode. In the DCP-EF process, H₂O₂ accumulation witnesses a 10% improvement along with a low-level energy consumption (31.16 W h/mol H₂O₂) compared to the conventional one. Aside from H₂O₂ improvement, a higher Fe³⁺ reduction rate (93.8%) is also observed than the conventional one with single CF system (71%), while total iron remains stable since iron precipitation near-cathode vicinity is alleviated in DCP-EF. A 98.5% sulfamerazine decay coupled with 85.6% mineralization confirms the superiority of the proposed system. Because a higher concentration •OH is detected than that of conventional one. In conclusion, the DCP-EF system is promising, coordinating H₂O₂ accumulation and Fe³⁺ reduction simultaneously.