| 1,2-dichloroethane is a typical volatile chlorinated alphatic hycarbon. It is widely used as solvent and chemical intermediates in many industries. Due to its high volatility and density, 1,2-dichloroethane leaks into the environment easily and then causing the pollution. The toxic 1,2-dichloroethane with carcinogenicity teratogenicity and mutagenicity is very stable and can be accumulated in the environment. This contaminant raises great chanllange to ecosystem and human health. 1,2-dicloroethane as a representive volatile chlorinated alphatic hycarbon has been listed on the priority controlled pollutants blacklist by many countries such as the USA and China. The emerging bioeletrochemical system have showed many advantages in deposing refractory pollutant such as high disposing rate, high removal rate and low energy consumption. It has already caused massive attention. But research on volatile chlorinated alphatic hycarbons degradation by biocathode is rarely reported.In this article, the activate sludge from secondary sedimentation tank in sewage treatment plant of wenchang is inoculated into bioeletrochemical system. Stable biocathode with well 1,2-dicholoethane degradation performance and biofilmm structure is gained after acclimatization. Degradation of 1,2-dechloroethane by biocathode is studied. The results show that when the applied voltage is-0.5V(biocathode’s potential about-0.58 V. VS.SCE), 1,2-dichloroethane can be reductively dechloriated to ethene in 12 hours. The current declines continuously with the 1,2-dichloroethane degradation at the same time. In 12 hours the current becomes stable. 1,2-dichloroethane’s decomposing rate reaches 0.15 m M?h-1,ethene recover rate is 77.51%. Under the same condition, 1,2-dichloroethane degration by abiocathode and ethene’s producing is not detected. Biocathode and open circuit biocathode(without applied voltage) is compared as well. Biocathade is 1.96 times faster than open circuit biocathade on 1,2-dichloroethane removal rate constant. This means the potential of biocathode greatly increase 1,2-dicholoethane decomposing rate. Cyclic Voltammetry technology is used to analysis the influence to biocathode after long term domestication. The results shows that compared to carbon brush cathode,the biocathode reductive peak rises about 0.32 V. This means that the biofilm of biocathode have promoted the reductive dechlorination of 1,2-dichloroehtane. We analysis the microbial community of biofilm. Pseudomonas and eight other genuses dominate the community. Pseudomonas(43.45%) and Lactococcus(33.29%)occupied the most part of the community the genuses with reductive dechlorination ability such as Geobacter Vadin BC27 and Solibacillus occupied 8.5% of the microbial community.We changed the applied voltage, initial concentration and carbon source to see their influence to 1,2-dichloroethane removal efficiency of biocathode. The results show that the decomposive rate of different voltage ranked from high to low is : 0.5V>0.3V>0.7V>0.9V, when the initial concentration is increased, the average current is raised, but the degradation rate drops. under the same condition, initial concentration of 2.2m M has a faster rate when the system changed into inorganic carbon(Na HCO3 replaces CH3COONa), the degradation rate constant of 1,2-dicholorethane apparently decreases(kinorganic= 0.0505, VS korganic=0.1286).but the convertion rate still remains high. In 12 hours, the removal rate reaches 48.71%. the recovery rate of ethene reaches 85.08%. This means cathode could be used as the only eletron doner and promotes the 1,2-dicholoethane reductively degradation. |
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