Coupling Of Autotrophic And Heterotrophic Denitrification In The Bio-cathode Using Paracoccus Sp. YF1 And Impact Of Nanoparticles On MFC

The aim of this research was to explore the coupling of autotrophic and heterotrophic denitrification in the bio-cathode using Paracoccus sp. YF1 and the effect of nanoparticles such as nano-graphene (N G) and nano-iron (nZVI) on the generation of electricity and degradation of organic substrate in the Microbial Fuel Cells (MFC).Fristly, in order to remove nitrate and generate electricity, the bio-cathode microbial fuel cell (MFC) using parococcus sp.strain YF1 was assembled in this study. Results showed that the carbon-nitrogen ratio and initial pH in the cathode had strong influence on the electricity generation and removal of nitrate, e.g,150 mV of voltage was output and 100% nitrate was removed after biodegradation for 15 h at pH 8.0 and C/N 20. Based above, it indicated that the degradation mechanism of nitrate from wastewater either by parococcus sp.strain YF1 could be through reduction to nitrogen or by being used directely as the nutrient reqired, and generate power at same time. In addition, Scanning Electron Microscope (SEM) and Cyclic Voltammetry (CV) analysis showed parococcus sp.strain YF1 was used to build up MFC, as electron donors for power generation by the direct contact.Secondly, the enhancement of voltage output by the addition of nanomaterial in the MFC is gaining its great popularity in recent years. In this part, I also evaluated the effect of nano-graphene(N G) and nano-iron(nZVI) impacting on the performance of MFC. New findings include that the highest voltage of MFC retained when the nZVI and N G was added into MFC, repectively, comparing with the control experiment. However, this cycle for generated electricty increased by 10 hours in the presence of 50 mg/L nZVI. On the contrary, the cycle of MFC’s operation was significantly reduced by 40 hours in the presence of 500mg/L N G, which was probably due to its toxicity to the bacteria on the surface of electrode in MFC, causing the process of electricity’s generation ended at 65h.In summary, the observation could be resulted from (1) since the aggregation of N G and nZVI can serve as carrier for the growth of microorganisms, thus promoted the COD’s reduction and the reduction of operate cycle in MFC. (2) the toxicity of NG on the both free cell in the solution and cell attached on the electrode surface was not obvious. In contrast, a low concentration of nZVI inhibited the growth of bacteria in the solution, but its impacts on microorganisms attached to the surface of electrode were limited. However, a high concentration nZVI particle was prone to aggregate in anode solution, supporting the metabolism of cells on their surface. Conseqtenly, they had negative influence on the bacteria of electrode surface, even leading to the death of these cells.