Shewanella Drive Fe(III) Reduction to Promote Electro-Fenton Reactions and Enhance Fe Inner-Cycle

The slow reduction of Fe(III) to Fe(II) in electro-Fenton technology limits pollutant removal and causes Fe sludge production. This study hypothesizes that Shewanella, a dissimilatory iron-reducing bacteria, can accelerate the iron reduction of the Fenton reaction. A Shewanella biofilm coupled with Fe2O3 coated electrode (F/S) was used to drive the electro-Fenton reaction, and compared the results with the singlet Fe2O3 (F) anode and Shewanella biofilm anode (S). Meanwhile, dissolved oxygen (DO) is studied as an important influencing factor. The suitable DO was verified at ∼2 mg/L, phenol removal of F/S was 67% higher than that of the sum of three other singlet systems. The chemical oxygen demand (COD) removal was 72% and 50% higher than that of F and S, respectively. F/S corrosion current (Icorr) was 6.3 times higher than F, and induced hematite to transform into Fe2PO5 and FeOOH on the anode. Long-term operation showed that phenol was almost 100% removed for F/S; COD removal was generally 20% higher than F; thus, the toxicity of the effluent could be significantly decreased. The total Fe loss did not exceed 10% at the end of operation. This paper provides a feasibly novel method for electro-Fenton reaction, by employing Fe-reducing bacteria.