reduction processes another process which involves electron transfer (except in the opposite...
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![Page 1: Reduction Processes Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example](https://reader035.vdocument.in/reader035/viewer/2022062320/56649d3f5503460f94a19393/html5/thumbnails/1.jpg)
Reduction Processes
Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example is the reductionof halogenated hydrocarbons.
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o 2
o 2
RX H 2e RH X
Fe Fe 2e
____________________________
RX H Fe Fe RH X
Reductive dehalogenation with zero valent iron:
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Hydrogen gas is usually inert but in the presence of Pd, Ni, Pt and possibly Feo hydrodehalogenation is possible.
M2H RX RH H X
It is also possible that Feo can react with H+ to form H2.
o 22Fe 2H Fe H
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![Page 5: Reduction Processes Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example](https://reader035.vdocument.in/reader035/viewer/2022062320/56649d3f5503460f94a19393/html5/thumbnails/5.jpg)
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![Page 7: Reduction Processes Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example](https://reader035.vdocument.in/reader035/viewer/2022062320/56649d3f5503460f94a19393/html5/thumbnails/7.jpg)
![Page 8: Reduction Processes Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example](https://reader035.vdocument.in/reader035/viewer/2022062320/56649d3f5503460f94a19393/html5/thumbnails/8.jpg)
![Page 9: Reduction Processes Another process which involves electron transfer (except in the opposite direction as AOP) is reductive dechlorination. An example](https://reader035.vdocument.in/reader035/viewer/2022062320/56649d3f5503460f94a19393/html5/thumbnails/9.jpg)
03 2 2 3 210Fe 6NO 3H O Fe O 6OH 3N
Other chemical species can be reduced by the iron.For example nitrate can be reduced to nitrogen gas:
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Potential long term problem:
As the dehalogenation process proceeds pH will rise as H+ is used. This could result in precipitation of
CaCO3 or FeCO3 which will ultimately reduce
porosity of the permeable barrier.
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Typical Design Results:
First order decay rate approx.
0.03 per hour ( half life = 20 hours)
With a Feo barrier of 1.2 m thickness and a flow rate through the barrier equal to 0.4 m/day get approx. 90% reduction in RX.