Effect And Mechanism Of Microbial Electrochemical Coupling On Degradation Of 2-Chloro-4-Nitrophenol

Chloronitroaromatics was hard to biodegrade because of their inherent molecular structure.Chloronitroaromatics have been listed as priority pollutants by the U.S.Environmental Protection Agency for they have high toxicity,teratogenicity,long residue time,and wide distribution in environment.Traditional biological treatments have some shortcomings such as low efficiency,long hydraulic retention time and chemical treatments?expecially advanced oxidation?are high cost.This experiment constructed a chloronitroaromatics wastewater treatment method with low cost and high treatment efficiency,which is bio-electrochemical system?BES?.In this experiment,2-chloro-4-nitrophenol?2Cl4NP?was used as the main pollutant,and treated at the cathode of reactor under the condition of anaerobic.The degradation products were analyzed by HPLC and HPLC-MS/MS.The main results are as follows:?1?Voltage can significantly accelerate the degradation of 2Cl4NP and 0.5v was the optimum voltage condition.Low or high voltage was not conducive to the degradation of 2Cl4NP,and low voltage had a greater effect on the deradation of2Cl4NP.In the condition of low voltage,the deradation of 2Cl4NP was extremely slow.?2?The initial substrate concentration had a great influence on the degradation of 2Cl4NP.The higher the initial concentration,the faster the degradation rate,the higher the degradation efficiency,the lower the initial concentration,the slower the degradation rate,and the lower the degradation efficiency,2Cl4NP could not degrade completely with the low initial concentration.?3?Co-matrix could affect the degradation of 2Cl4NP.The degradation efficiency was poor and cannot be completely degraded when using sodium acetate as a co-substrate.The degradation efficiency was much better when using glucose as a co-substrate.But the degradation efficiency was best when without matrix.?4?The degrdation products of 2Cl4NP were 2-chloro-4-nitroaniline,para-aminophenol,2-chlorohydroquinone and 2-chlorophenol,and 2-chlorophenol was the main product of 2Cl4NP degradation.Then the 2-chlorophenol was continue reduced and finally genarate CO₂ and H₂O.?5?Salt bridge cannot replace proton exchange membrane as proton exchange channel of BEC reactor.Under the connection of salt bridge,voltage could influence the degradation of 2Cl4NP and 0.9v was the optimum voltage condition.But the degradation under voltage was poorer than without voltage.The degradation products were analyzed by HPLC-MS/MS and found that 2-chloro-4-nitrophenol degrade to form2-?2-chlorophenoxy?acetamide,2-chloro-4-nitrotoluene,2,6-dichloroindophenol and O-chlorophenolindophenol under the connection of salt bridge.The cause of the difference was not clear yet.