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 Fe 2 O 3 coated electrode (F/ S ) was used to drive the electro-Fenton reaction, and compared the results with the singlet Fe 2 O 3 (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 ( I corr ) was 6.3 times higher than F, and induced hematite to transform into Fe 2 PO 5 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.