Study On Reduction Of Nitrophenols By Bio-electrochemistry Technology

In this study, a bio-electrochemical system was designed to investigate the reduction of ONP、MNP、 PNP under different parameters (cathode potential、the cathode of hydraulic retention time, et al.). Their reductive pathways and their reductive performances were investigated and compared.The results indicated that MNP and PNP were well transformed to their corresponding aminophenols, without further transformation. While most of ONP was changed to intermediate products and be removed through polymerization, resulting lower concentration of2-aminophenol in effluent. The removal efficiency, removal rate of nitrophenols, the coulomb efficiency of both cathode and anode, increased as the cathode potential decreased from-300mV vs Ag/AgCl to-700mV vs Ag/AgCl. Power output was gained when cathode potential was higher than anode potential, and with the decrease of cathode potential, power output decreased and was gradually transformed to energy input when cathode potential was lower than anode potential. Power input increased with the decrease of cathode potential. At prolonged HRT, the removal efficiency of nitrophenols was higher, while the removal rate and power input was lower.In the cathode potential of-700mV vs Ag/AgCl, HRT of2.6h, the removal efficiency of ONP, MNP, PNP was100%,97.2%and95.3%, respectively. The results indicated that the removal rate of nitrophenols followed the order of ONP>MNP> PNP, under the same conditions. The calculation of electron cloud density, the frontier orbital energy, and the cyclic voltammetry analysis demonstrated the results. The calculation of electron cloud density was consisted with the results of experiment. At the same conditions, the electron donor usage of7.45mol COD mol-1ONP,7.65mol COD mol-1MNP,7.81mol COD mol-1PNP was gained respectively, which was slower compared with that of conventional anaerobic methods; In addition, the power consumption was0.0323kWh mol-1ONP,0.089kWh mol-1MNP and0.097kWh mol-1PNP, respectively, which was far lower than those in pure electrochemical systems; The biodegradability and acute toxicity of nitrophenols treated have also been improved. So the efficient treatment of nitrophenol wastewater could be achieved in the bio-electrochemical system.