Feasibility Of Nitric Oxide As Electron Acceptor Of Microbial Fuel Cell Cathode And Transformation Process

As nitrogen oxides(NOx) being one of the problems that cause global air pollution, complexing absorption biological nitrogen oxides reduction is an emerging technology of denitration. However, with high cost of complexing agent and large energy consumption of regeneration, this technology meets its bottleneck problem.Microbial Fuel Cell(MFC) can make an achievement about the removal of organic pollutants and efficient production of electricity. With the combination of the MFC’s electricity generation and nitrogen oxides’ s removal technology, this thesis puts forward a new idea — taking nitrogen oxides as election acceptor so as to realize the goal to treat wastes with processes of wastes against one another.In this paper, we first investigated the feasibility of NO as a MFC cathode electron acceptor. We constructed a 28 ml cubic single chamber reactor, and the anode was a carbon brush, the cathode was carbon rolled cathode. Drainage method was used to achieve pure NO as electron acceptor, and the output voltage of single chamber MFC reached up to 380 MV. It is proved that NO can be used as an electron acceptor in the cathode of MFC reactor.The accumulation of nitrite and nitrate in the reactor was found when the NO was the electron acceptor. In this study, we constructed two configurations of the reactors, a cubic MFC and a membrane cubic MFC, at the same time, the method of electrochemical reduction was used to explore the nitric oxide transformation process. The results show that nitrite and nitrate oxidation by-products in the reaction process will be accumulated, at the condition of higher potentials and higher H+ concentration, reduction products are NH4+ and N2, at lower potentials, the reduction products may be N2 and N2 O.Because of the low solubility of NO in water, the mass transfer efficiency is not high. Therefore, citric acid(CIT) was used to carry out the complexation of NO and the feasibility and influence factors of the complex were investigated. The experimental results show that Fe(III) CIT and Fe(II) CIT-NO as the MFC cathode electron acceptor, and the regeneration of Fe(II) CIT is feasible. The p H of cathode electrolyte(Fe(II) CITNO and Fe(III) CIT) in the reduction of cathode influence the MFC electrical property. The initial Fe(III) CIT concentration is higher, the electricity production performance is better.The experimental also designed a MFC reactor with a 600 m L anode and a 180 m L filler cathode, it was operated with nitric oxide as electron acceptor and also a 600 ml cubical reactor as before were compared. The effects of temperature, HRT and external resistance on the electrical properties of MFC is researched. The results showed that the best temperature is 30 ℃ as experimental temperature. The hydraulic retention time 6h, 12 h and 24 h were compared, the result was the shorter the hydraulic retention time, the higher the MFC performance and the better the removal of NO we can get. The small resistance of MFC and NO is better, and the MFC property is better and the NO removal rate is higher in the experiment 20 Ω. The most favorable condition for the laboratory is 30 ℃, HRT 6 hours, and the external resistance 20 Ω. At the same time compared with simple cubic reactor, the filler cathode reactor is more suitable for continuous intake gas, whose practical value is higher.