Enhancing The Electricity Generation And Sludge Reduction Of Sludge Microbial Fuel Cell With Graphene Oxide And Graphene

Sludge microbial fuel cell(SMFC)is capable of extracting biomass energy directly from the excess sludge and runs in a single chamber without a proton exchange membrane to achieve sludge reduction while generating electrical energy.However,most of organic matters in the excess sludge are the cell substances that are difficult to be used by microorganism directly.In this paper,adding graphene oxide(GO)and reduced graphene oxide(rGO)in SMFC was proposed and their advantages were reflected by no requiring external energy,in-situ breaking cells,promoting the electricity production and reducing sludge effectively.The results showed that GO and rGO had the function of breaking cell and accelerated electrons transporting,so they could greatly promote the sludge reduction and electricity production of SMFC.The contents of lactate dehydrogenase(LDH)for adding 0.4 g GO in SMFC(0.4-GO SMFC)and adding 0.4 g rGO in SMFC(0.4-rGO SMFC)were 2 and 1.81 times higher than that of adding nothing in SMFC(ordinary SMFC),indicating that GO and rGO effectively broke the cell.Three-dimensional fluorescence spectroscopy analysis illustrated that the addition of GO and rGO in SMFC could promote the utilization of organic matter such as dissolved microorganism byproduct and humic acid.Sludge reduction rate of 0.4-GO SMFC and 0.4-rGO SMFC were 3 and 2.2 times that of ordinary SMFC,respectively.The removal rate of TCOD in 0.4-GO SMFC and 0.4-rGO SMFC achieved 50.8% and 40%,which increased by 198% and 156%.The maximum power density for 0.4-GO SMFC and 0.4-rGO SMFC were up to 214.09 mW/m3 and 80.52 mW/m3,respectively.Their internal resistances were 1126.8 Ω and 2027.1 Ω and decreased by 71% and 48% separately in contrast with ordinary SMFC.And their corresponding maximum voltages were 0.483 V and 0.313 V respectively,which were 2.34 and 1.52 times that of ordinary SMFC(0.206V).The results also demonstrated that SMFC with adding GO acquired much better performance of electricity production and sludge reduction than SMFC with adding r GO,and it was attributed to the hydrophilicity of GO,increasing the diffusion performance of the sludge mixture and reducing the diffusion resistance.Raman spectrum analysis revealed that the GO on the anode surface was successfully reduced to rGO in situ by microorganisms.Compared with chemically reduced rGO,microbially-reduced rGO had better biocompatibility and less biological toxicity,and made microorganisms adapt to the environment more quickly.