Research About Reduction Of Chloronitrobenzenes Synergistically Catalyzed By Biopd And Shewanella Oneidensis MR-1

Chloronitrobenzenes(CNBs)are a group of toxic chemicals which cause carcinogenic,teratogenic,mutagenic and even genotoxic.CNBs are widely used for pesticides,dyes and other industrial chemicals.China is one of major produce and applications countries.Therefore,due to not up to standard about wastewater treatment and use,CNBs are found throughout environment in surface water,soil,and groundwater which threatens human health and destroys the ecological environment.The biological method has low cost,high efficiency,no secondary pollution,and another advantages so that it is more concerned by environmental researchers for the treatment of chloronitrobenzenes.Microbial synthesized palladium nanoparticles(bioPd)have demonstrated a great activity toward dechlorination of several chlorinated pollutants.Shewanella oneidensi MR-1 is a facultative anaerobic bacterium which has the strong ability of reducing and dissimilating so that it can synthesize the particle of bioPd.Chlorinated organic compounds can be dechlorinated by bioPd and S.oneidensis MR-1.Regrettably,there was few that researchers explored reduction pathway and mechanism of chloronitrobenzenes synergistically catalyzed by bioPd and S.oneidensis MR-1.In the thesis,research purpose was that explored the reduction pathway and mechanism of chloronitrobenzenes synergistically catalyzed by bioPd and S.oneidensis MR-1.BioPd was synthesized by S.oneidensis MR-1.The dechlorination of 2-chloronitrobenzenen(2-CNB),4-chloronitrobenzene(4-CNB)and 2,4-dichloronitrobenzene(2,4-DCNB)catalyzed by bioPd were investigated and analyzed.Main contents and results are as follows:1.BioPd reduced by S.oneidensis MR-1 with formic acid as electron donor that bioPd were mainly distributed in the cell surface and cell gap.The investigation had shown that chloronitrobenzenes could be reduced by S.oneidensis MR-1 with synergistically bioPd catalyzed.There was Pd concentration optimized for the reduction which cultures pretreated with 100 ?M Pd(?)demonstrated the most effective catalysis towards CNBs reduction.2.The reduction of 2-CNB found that nitrobenzene(NB)and 2-chloroaniline(2-CAN)were intermediate products and Aniline(AN)was the final product,while nitrobenzene(NB)and 4-chloroaniline(4-CAN)were intermediate products and Aniline(AN)was the final product for the reduction of 4-CNB.At the best performance synergistically bioPd catalytic system,not only the reduction rates increased in proportion to the initial concentrations of 2-CNB/4-CNB,but also their initial concentrations were not to exceed 2.5 mM otherwise could not fully reduced to final products.What's more,results implied that CNBs in the dechlorination reaction were more difficult than the conversion of nitro and position of chloro groups affected the reduction of CNBs in this system.3.When 2,4-DCNB was reduced in the most effective catalytic reduction system,its intermediate products were 2-CNB?4-CNB?2-CAN?4-CAN.2,4 dichloroa-niline(2,4-DCAN)?NB and its final product was also AN.Under the same conditions,reduction intermediate products of 2,4-DCAN were 2-CAN?4-CAN,fortunately,they had the same final product.On one side,2,4-DCNB studies had shown that removal of chlorine atom at para position was easier than that at ortho position.On the other side,2,4-DCAN studies had shown that remove of chlorine atom at para position was more difficult than that at ortho position.According to these results,we summarized the pathway of 2,4-DCNB reduction to AN in our catalytic system.Especially,it was supported by DFT(Density Functional Theory)calculation that the removal of chloro groups in 2,4-DCNB suggested a position effect on dechlorination in our catalytic system.