The Relationship Between Bio-electrochemical Reduction Of Nitrophenols And Their Molecular

In this study, a bio-electrochemical system was designed to investigate the reduction of 4-nitrophenol (PNP),2,4-dinitrophenol (DNP),2,4,6-trinitrophenol (TNP) under different patameters such as cathode, pH of cathode inffluent, et al. Possible reduction products of the three nitrophenols were explored, and the reductive rule was analysed.When different electrodes were applied in bioelectrochemical system, it was found that the BES with graphite particle electrodes is superior to that with graphite felt electrodes on both PNP degredation and PAP formation. The excellent reduction effect of nitrophenols depends on a large specific surface area and small internal resistance of electrode materials,In the bioelectrochemical system, both of the three nitrophenols were reducted. PNP was transformed to PAP, without any further convertion; because of the instability of DAP, the final reduction product of DNP, there was only the intermediate reduction product 2-A-4-NP detected in the effluent; TNP was first reduced to 2-A-4,6-DNP, and most of 2-A-4,6-DNP was transformed to unkown products. The acute toxicity of PNP and DNP can be improved to a certain extent after bioelectrochemical reduction. Howerver, the acute toxicity of the reduction product of TNP became stronger.When cathode potential was controlled from-300 to-700mV vs Ag/AgCl, the removal efficiency and rate of NPs became larger, indicating that a low cathode potential is more conductive to NPs reduction; when the pH of cathode inffiuent was changed from 4 to 9, the removal efficiency and rate of NPs gradually diclined, indicating that the reduction effect of NPs is closely related with the amount of H+ in aqueous solution. Under acidic condition, the order of NPs removal efficiency is PNP>DNP>TNP; however, that of NPs removal efficiency is DNP>TNP>PNP under alkaline conditions. Experiments showed that, NPs removal efficiency depends on the electron cloud density of nitrogen atoms, ionization in aqueous solution,the amount of nitro-groups and so on.