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This study introduces a tartrate-EDTA-Fe complex as a soluble electron mediator (EM) in bioelectrochemical systems (BES) coupled with ammonia stripping units. The complex enables efficient electron transfer at the cathode while allowing aeration only at the stripping column, eliminating the need for multiple aeration points. At RC-A = 12, the system achieved 6.9 ± 0.2 g N m⁻² d⁻¹ NH₄⁺-N recovery—3.8 times higher than non-EM controls—while maintaining comparable performance to prior work at drastically lower recirculation ratios (0.5 vs. 288), simplifying system design for scale-up.

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Abstract

Traditional bioelectrochemical systems (BESs) coupled with stripping units for ammonia recovery suffer from an insufficient supply of electron acceptors due to the low solubility of oxygen. In this study, we proposed a novel strategy to efficiently transport the oxidizing equivalent provided at the stripping unit to the cathode by introducing a highly soluble electron mediator (EM) into the catholyte. To validate this strategy, we developed a new kind of iron complex system (tartrate-EDTA-Fe) as the EM. EDTA-Fe contributed to the redox property with a midpoint potential of -0.075 V (vs. standard hydrogen electrode, SHE) at pH 10, whereas tartrate acted as a stabilizer to avoid iron precipitation under alkaline conditions. At a ratio of the catholyte recirculation rate to the anolyte flow rate (R C-A ) of 12, the NH 4 + -N recovery rate in the system with 50 mM tartrate-EDTA-Fe complex reached 6.9 ± 0.2 g N m -2 d -1 , approximately 3.8 times higher than that in the non-EM control. With the help of the complex, our system showed an NH 4 + -N recovery performance comparable to that previously reported but with an extremely low R C-A (0.5 vs. 288). The strategy proposed here may guide the future of ammonia recovery BES scale-up because the introduction of an EM allows aeration to be performed only at the stripping unit instead of at every cathode, which is beneficial for the system design due to its simplicity and reliability.

Keywords

Stripping (fiber)AmmoniaOxidizing agentTartrateCathodeInorganic chemistry

Identifiers

DOI
10.1016/j.ese.2022.100186
PubMed
36158760
Journal
Environmental Science and Ecotechnology
Year
2022