• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Determination Of The Degradation Mechanism For Polychlorinated Biphenyl Congeners Using Mechanically Alloyed Magnesium/palladium

DeVor, Robert 01 January 2008 (has links)
Polychlorinated biphenyls are a ubiquitous environmental contaminant that can be found today throughout the world in soils and sediments, lakes and rivers, and flora and fauna. PCBs have percolated throughout the food chain, so that almost every human being has a detectable amount of the contaminant within their blood stream. Existing remediation methods include incineration, dredging and landfilling, and microbial degradation, but all of these methods have drawbacks that limit their effectiveness as treatment options. Recently, the use of zero-valent metals as a means of reductive dechlorination has been explored. Using a combination of zero-valent magnesium and catalytic palladium, a successful bimetallic system capable of degrading PCBs has been created and optimized. Determining the mechanism for the reductive dechlorination has proven to be an arduous task, but experimental evidence has suggested three possible radical-type mechanisms for the use Mg/Pd specifically in methanol (as compared to aqueous systems). These possible mechanisms differ in the type of hydrogen species that replaces the chlorine atom on the PCB. Thermodynamic information has also aided in narrowing down which of the suggested pathways is most likely. It appears likely that the hydrogen involved in the dechlorination has the form of a "hydride-like" radical, which is a form of electron-rich atomic hydrogen. According to the literature, Pd catalysts create this species within the first few subsurface layers of the palladium in the presence of molecular hydrogen. Further work will be necessary to confirm that the "hydride-like" radical is actually the species involved in the dechlorination.

Page generated in 0.0559 seconds