Study On Mechanisms Of Electrolysis-enhanced Anaerobic Digestion Of2,4-dinitrochlorobenzene(DNCB)

2,4-dinitrochlorobenzene (DNCB) is an important chemical raw material, widely used in pesticides, pharmaceuticals, dyes, explosives, rubber plastics and other fields. DNCB is chemically stable and has carcinogenesis, teratogenesis, mutagenesis and genotoxicity. The EPA of USA, the European Community (EEC) and China have declared that chloronitrobenzenes are the priority pollutants. Therefore, it is important to develop efficient and cost-effective technologies for the control of toxic organic contaminants. Based on the advantages of anaerobic biological treatment and bioelectrochemical catalytic reduction, the mechanisms of electrolysis-enhanced anaerobic digestion of DNCB are investigated in this paper.The results of researching on the impact of various parameters are as follows:at the external voltage1.4V and the methanol concentration1500mg/L, the removal of DNCB in electricity-anaerobic biological coupling system is the best at DNCB initial concentration100mg/L and HRT120h.Low salinity (<1%) is conducive to stimulate microbial growth, however, the high salinity decreased dechlorination in reactor. At the external voltage1.4V and HRT120h, the electricity-anaerobic biological coupling system can deal with DNCB at maximum concentration of200mg/L.The experiment demonstrated that conversion rate of2,4-diaminochlorobenzene (DACB) in electricity-anaerobic biological coupling system, anaerobic system and electrochemical system was27.5%,17.9%and1.4%, respectively. The results of PCR-DGGE showed that the microbial communities in the reactor and conventional anaerobic reactor were diverse. The electric field had inhibitory effect on the growth of methylomonas, while producing electricity microbes enriched, which is conducive to the oxidation of methanol.The mechanism of electrolysis-enhanced anaerobic digestion of DNCB has been studied by HPLC, GC-MS methods. The results show that in the electricity-anaerobic biological coupling system, nitro group on DNCB was degraded into amino group, and the ortho nitro group was easier to be degraded and eventually converted to DACB. In the reactor, DACB could be reductively dechlorinated using methanol as the electron donor, with m-phenylenediamine as product.In summary, the electricity-anaerobic biological coupling system favors the participation of both electrochemical and microbial degradation, reflects catalytic reduction by the electric field. DNCB can be transformation efficiently in the electricity-anaerobic biological coupling system by electric field domesticating microorganisms and electrolysis of water. This paper may provide a novel integrated technology for the treatment of recalcitrant wastewaters.