How can a solvent be used to remove hydrocarbons from soil samples?

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Offline salmike

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Hello, new to the forum, hoping someone can help.

I currently work in an organics department in an enviromental company, doing solvent extractions for hydrocarbons (all) ( the wrong field for me really as im a biologist and doing this as a industrial practice position in a different field)

Im currently writing a review as a peice of university work and have become baffled.

Im really stuck on understanding the interactions between solvent and analyte when testing soils. Does the solvent bind to the hydrocarbon?does it simply change the polarity to allow it to become misicible? does it change the structure?  (basically im pulling my hair out)

Once ive conqured this barrier i can continue.

Can anyone help me out...prefereablly with a simple explained straight forward diagram...designed for a 2year old? hehe j/k

anyway thanks

mike
« Last Edit: 03/06/2008 12:10:07 by chris »

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Offline Bored chemist

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I will try to help, but I'm a bit uncertain what you are doing.
If I wanted to measure the hydrocarbons in (for example) soil I would wash them out with some suiable solvent. Filter out the solid soil then analyse the solution.
I'm not sure what solvent I'd use, probably dichloromethane.
The extraaction process isn't anythng magical. The analyte simply dissolves in it.
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Offline pangallo

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Hi salmike,

Bored chemist is correct - what is going on is that the hydrocarbons are more soluble in the solvent used for extraction than in the soil matrix.   The hydrocarbons are probably associating with the layer of organic matter present in all soil.  When you add a solvent, both this organic matter, as well as any hydrocarbon associated with it, will dissolve in the solvent.  It shouldn't change the structure of the hydrocarbons in any way.  However, you will be extracting more than just the hydrocarbons - you will be getting lots of 'natural' organic compounds that are present in soil.  It is also possible that some of the hydrocarbons will stay with the soil.  Sometimes these compounds can bind to the mineral particles and a simple soil extraction will not remove them - more intense chemistry is necessary.  Hydrocarbon analysis is a very active area of research (just think of all the oil companies) so there should be plenty of literature out there on this topic.  You might want to focus in on the environmental chemistry literature.

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Offline tedstruk

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Can hydrocarbons be burned out of contaminated soil?

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Offline chris

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Yes they can, and this is how some soils from sites undergoing remediation and decontamination - for instance prior to redevelopment as a housing estate - are cleaned up.

Chris
I never forget a face, but in your case I'll make an exception - Groucho Marx