Effect And Mechanism Of Microbial Bioelectrochemical System On Degradation Of 2,5-dichloronitrobenzene

Chloronitrobenzenes（abbreviation ClNBs）as the synthesis chemical intermediates,are widely used in the manufactures of chemicals.This compounds have mutagenicity and genotoxicity,and could be accumulated in sediments and soils and then threaten ecological security and human health.Because of the serious environmental issue,these compounds have been decleared to be priority pollutants by EPA,EEC and china.Consequeently,there are significant demands of efficient and cost-effective technologies for ClNBs wastewater treatment.In this study,2,5-dichloronitrobenzene q（abbreviation 2,5-DCNB）was used as target pollutant,and the electrochemical anaerobic sludge couple system and the upflow bioelectrochemical system were used to treat 2,5-DCNB.The characteristics of 2,5-DCNB degradation and possible degradation pathways were analized by HPLC and IC and LC-MS.The main results are as follows:1.The electrochemical-anaerobic sludge couple system has batter degradation efficiency than the anaerobic sludge systen.Under the neutral situation,when the initial concentration of 2,5-DCNB was 30 mg·L^-1,external voltage was 0.5 V and the react time was 36 h,the removal rate of 2,5-DCNB reached 99%.the removal rate of 2,5-DCNB were affected by the applied voltage,carbon source of wastewater and sludge dose.When the external voltage increased from 0.25V to0.5V,2,5-DCNB degradation rate in the system was positively correlated with the voltage value,When the external voltage exceeded a certain limit,the rate of degradation reduced promptly.Adding an appropriate amount of carbon source to system was beneficial to the 2,5-DCNB degradation.when the concentration of the carbon source exceeds 3g·L^-1,the inhibition effect was exhibited.In addition,the increase of sludge dose would enhance the remove of 2,5-DCNB in coupled system.2.Multiple groups of up-flow bio-electrochemical system（abbreviation UBES）have been constructed,the cathode was placed in the sludge,and the anode wan placed in water.Results showed that,the UBES treatment performance was affected by applied voltage and influence COD concentration.Under the neutral situation,when the initial concentration of 2,5-DCNB was 30 mg·L^-1,external voltage was 0.5 V and the react time was 18 h,UBES has higher processing efficiency and stability for 2,5-DCNB than electrochemical-anaerobic sludge coupled system.Under the optimal conditions,the react time was 24 h,the removal rate of 2,5-DCNB reached 99%.3.The intermediates after degraded for 36 hours were analized by HPLC and LC-MS and IC,which showed that concentration of Cl^-1 in system reached 5.31mg·L^-1after 28h of reaction.At the same time,it produces a variety intermediated products during the degradation process,presumabiy 2,5-dichloronitrosobenzene,2,5-dichloroaniline,2-chloroaniline,aniline,n-hexanoic acid,2-chloronitrosobenzene,benzenediol,succinic acid,etc.