Degradation of refractory organics in dual-cathode electro-Fenton using air-cathode for H2O2 electrogeneration and microbial fuel cell cathode for Fe2+ regeneration

Highlights: • Dual-cathode electro-Fenton was realized by coupling air-cathode with MFC cathode. • Fe²⁺ regeneration was accelerated through Fe³⁺ reduction on CF cathode of MFC. • RhB removal rate was 64% higher than electro-Fenton without coupling MFC cathode. • MFC power generation was enhanced by 480% due to higher Fe³⁺/Fe²⁺ redox potential. The electrogeneration of H₂O₂ and electro-regeneration of ferrous are conflicting matters in electro-Fenton system. In this research, the degradation of Rhodamine B, methyl orange (MO) and 4-chlorophenol (4-CP) was investigated using a novel dual-cathode microbial fuel cell (MFC) electro-Fenton (EF) hybrid system. An air-cathode of an EF system was used for H₂O₂ electrogeneration and a carbon felt cathode of a MFC was used to accelerate Fe²⁺ regeneration. Synergistic improvement of MFC power generation and the degradation of the above refractory organics through EF reaction was achieved. The EF air-cathode was fabricated by adopting activated carbon/graphite powder mixture and PVDF binder, which showed higher H₂O₂ generation but slower Fe³⁺ reduction rate than MFC carbon felt cathode. The Rhodamine B removal rate constant and mineralization current efficiency of the MFC coupled EF were 64% and 42% higher than that of uncoupled EF, respectively. The MFC-EF coupled system also exhibited significantly higher removal efficiency for MO and 4-CP than that of un-coupled EF system. Moreover, the power density of MFC was greatly enhanced by coupling EF due to higher Fe³⁺/Fe²⁺ redox potential than oxygen reduction.