Nitrogen oxide gas purification using carbon in water as reducing reagent with the aid of microbial fuel cell

Highlights: • MFC can remove NOx by using carbon in water as reducing reagent. • The cathode with high activity greatly enhanced the NO_X removal efficiency. • The coexistence of O₂ with NO increased both the NOx removal and power output. • MFC maintained good stability for NO_X removal. Microbial Fuel Cell (MFC) can degrade the organic matter (OM) in wastewater at the anode and transfer electrons to the cathode. In this work, the harmful NO_X gas was used as electron acceptor in MFC and converted to harmless N₂. The OM in water was indirectly used as a zero-cost reducing agent for NOx removal. More than 80% of NO_X was removed continuously by MFC at room temperature. The NO_X was directly reduced to N₂ at MFC cathode and the cathode activity played a key role on enhancing the NO_X removal. The NO_X removal efficiency by the cathode of high potential was 1.37 times that by the cathode of low potential. When O₂ coexisting with NO as the electron acceptor, not only the NO_X removal but also the power output of MFC was improved greatly. The presence of NO_X did not decrease the power generation of MFC under the same O₂ concentration. The MFCs showed good stability for NO_X treatment and power output. Moreover, the possible pathways and advantages of NO_X removal by MFC were discussed in detail. These results indicated that the MFC system has the potential to treat wastewater, purify flue gas and recover energy simultaneously.