[Dechlorination mechanisms of chlorinated hydrocarbons by supported nanoscale Pd/Fe].

Some volatile chlorinated hydrocarbons such as VC,1,1-DCE,TCE,PCE, γ-HCH,were dechlorinated by synthesized supported nanoscale Pd/Fe.The dechlorination reactions of PCE,TCE,1,1-DCE,VC,γ-HCH follow the pseudo-frist order kinetics equations with the k_(obs) of 2.79 h~(-1),2.35 h~(-1),1.12 h~(-1),2.14 h~(-1) and 4.02 h~(-1) respectively.Little or no medial products were detected and the main end products were C_2H_6 and C_2H_4 during the dechlorination of VC,1,1-DCE, TCE,PCE.The total carbon ratio of C_2H_6 and C_2H_4 were 70% and 10% respectively during the dechlorination of TCE.The supported nanoscale Pd/Fe particles after exposed to air for 24 h were used for 8 cycle experiments and the results indicate that the particles have favorable stability.The reactivity has no obvious decrease after 200 hours' successive dechlorination experiments of γ-HCH which indicates that the particles represent good durability.The reaction activation energy of all the chlorinated hydrocarbons are bigger than 29(kJ·mol)~(-1) which shows that the surface-chemical reaction rather than diffusion is the rate-limiting step in the metal-mediated dechlorination process.A consistence between the experimental data and simulated curves indicates that the muti-step reaction pathways proposed offer a better explanation of the reaction mechanisms than sequential hydrogenolysis reactions in the transformation of chlorinated hydrocarbons by supported nanoscale Pd/Fe.