Three-dimensional Electrode Microbial Fuel Cells For Advanced Oxidation Of P-nitrophenol In Aqueous Solution

The efficient removal of refractory organic pollutants from aqueous solution is a hotspot in the field of environmental research.The development of clean engineering technology becomes an urgent issue due to energy shortage.In this work,a noval three-dimensional electrode microbial fuel cell?MFC?was constructed and the oxygen reduction cathode was investigated to enlarge the MFC application range from a device of energy output to a reactor of hydrogen peroxide production.At the same time,the concept of microbial electrolysis cell was introduced to further increase the yield of hydrogen peroxide.Based on cathodic hydrogen peroxide production,a three-dimensional electrode MFC-Fenton system was established by adding ferrous ions to the system or loading ferric oxides on cathodes to degrade p-nitrophenol?PNP?in aqueous water.The main contents and results are listed as follows:Carbon-PTFE particle electrodes were developed as three-dimensional cathodes of MFC,which showed that MFC with carbon three-dimensional electrode is a cost-effective energy-saving bioelectrochemical system for the simultaneous production of hydrogen peroxide and removal of COD.The MFC using graphite-PTFE particle electrodes?MFC-GPEs?was presented to perform the best in catalyzing H2O2 production but achieve lower power output.At high current?external resistance of 20 ??,MFC-GPEs achieved the H2O2 generation of 196.50 mg×L^-1 and 84% COD removal in 24 h.Applied voltage to MFC-GPEs was demonstrated to increase the productive rate,output of H2O2 and the efficiency of acetate degradation.In addition,a relatively high voltage leads to the reduction of H2O2 and the evolution of H2.Considering H2O2 concentration,anodic COD removal and current efficiencies of MFCs at various voltages,the optimal voltage was chosen to be 0.4V,achieving the H2O2 generation of 705.6 mg×L^-1 at a rate of 2.12 kg×m-3×day^-1 and 76% COD removal in 8 h,with energy input of 0.659 kWh per kg H2O2.A three-dimensional electrode MFC-Fenton system was constructed using GPEs to degrade PNP in aqueous solution.The MFC-Fenton system showed good performance of PNP degradation and TOC removal over a short period since PNP was absorbed in and surrounded by GPEs,which have kinetic favorability in degradation.Low pH,high current density and moderate iron dosage enhanced PNP elimination.Under optimal conditions(PNP concentration of 0.050 mol·L^-1,pH 3,iron concentration of 0.025 mol·L^-1,a loading resistance of 20 ?),the three-dimensional MFC-Fenton system achieved 95.7% PNP removal?within 8 h?.Furthermore,the system had the stability for PNP elimination?⁹0 %?and electricity generation over durations as long as 96 h.Ferric oxide loading graphite particle electrodes?FO/GPEs?were prepared as the cathode of a three-dimensional electrode MFC-Fenton system?FO/GPEs MFC-Fenton?.Higher surface area and more mesopores of FO/GPEs contributed to higher oxidation and better performance of electricity generation.The application of FO/GPEs MFC-Fenton system on degrading PNP presented high catalytic efficiency in a wide range of pH value.The removal of p-nitrophenol and TOC attained to about 85 % within 8 and 64 h at neutral pH,respectively.A neutral FO/GPEs MFC-Fenton oxidation mechanism was a combination of typical Haber–Weiss mechanism and heterogeneous surface-catalyze reactions.