The MFC-driven Electrocatalytic Reduction Of Nitrate With Cu-Pd Composite Catalyst Modified Cathode

The increase of nitrate in water environment is not only a cause of eutrophication but also a potential threat for human health. Regarding to these facts, it stimulates people great concern on nitrate contamination in water. Electrocatalysis reduction method is a promising nitrate pollution treatment technology, but there are two limiting factors of its application. On the one hand, electrocatalysis process need to consume a lot of electricity, on the other hand, catalyst always use precious metal materials.In order to overcome these shortcomings, in this paper, microbial fuel cell technology was used to drive electrocatalytic reduction of nitrate, anode exoelectrogen degrades organism to produce electrons, electrons flow to the cathode through external circuit to reduct electron acceptors(NO3--N). Cu-Pd bimetallic catalyst was composited with polypyrrole (PPy) or titanium dioxide (TiO2 to form PPy-Cu-Pd stainless steel wire mesh electrode and TiO2-Cu-Pd carbon cloth electrode, which was used as the cathode electrode. Scanning electron microscopy(SEM) and x-ray energy spectrometry(EDX) results indicated that Cu-Pd electrode tended to form cluster, while PPy and TiO2 increased catalyst specific surface area, dispersed the bimetal more uniformly and reduced aggregation. Electrocatalytic activity was evaluated by reduction of nitrate in MFC cathode chamber. After 5.5 h reaction, the removal rate of NO3--N was 29.3% in Cu-Pd electrode system, the biggest cell potential was 0.218 V and the biggest power density was 30mW/m3, internal resistance was about 500 ?. When the polymerization time of PPy was 150s, the removal rate of NO3--N was 35.5% in PPy-Cu-Pd electrode system, which is increased 6.2% than Cu-Pd electrode, the biggest cell potential was 0.269 V, and the biggest power density was 50mW/m, which is 1.67 times of the Cu-Pd electrode system, internal resistance was about 200 ?. TiO2-Cu-Pd electrode calcinated at 450? had the highest catalytic activity, the removal rate of NO3--N was 59.2% in TiO2-Cu-Pd electrode system, which is increased 29.9% than Cu-Pd electrode and increased 27.3% than PPy-Cu-Pd electrode, the biggest cell potential was 0.550 V, the biggest power density was 120mW/m3, which is 4 times of the Cu-Pd electrode system and 2.4 times of the PPy-Cu-Pd electrode system, internal resistance was about 100 Q. Moreover, Using 450? TiO2-Cu-Pd electrode as the cathode electrode, removal rate of nitrate in MFC system increased with the external resistor reduction first and then reduced, when connecting with 500? external resistor, TiO2-Cu-Pd electrode system exhibited the highest removal rate of NO3--N, which was 71.6%. Reducing metal doping concentration, removal rate of NO3--N increased first and then reduced, and got highest at 0.25% pd doping concentration, which was 65.46% at 1000? resistance. Even if Pd doping concentration was 0.125%, the removal rate of NO3--N can still reach 60.10%. The main product was gas in all of this reactions.