Re: [Ifeffit] Preparation help with fly ash sample with diluted Tl

Thank you so much! This is the first time I tried to use ifeffit mailing list. I would have never expected so many responses from so many scientists. I wish one day I could be able to contribute back to this great scientific community as well! Thanks again! Mengling On Thu, Sep 29, 2011 at 8:00 PM, Matt Newville wrote:

Hi Mengling,

2011/9/29 Mengling Yi Stuckman :

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Thanks for all the response! They are all very helpful! Just want to make sure that I get the information right and a few follow-up questions: 1. I'd better contact the beamline engineer to ask for the sensitivity for Tl.

Yes!

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2. Fe fluorescence interference could be decreased by adding a few layer of Al foil. I knew that I did that when I measured As fluorescence. So this is ok.

Yes.

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3. Pb fluorescence interference is very hard to eliminate. Therefore, EXAFS for Tl is very hard to get. Actually, I didn't see any papers on Tl EXAFS and maybe that is why. The research question I want to answer is: what structure Tl is bond to in the fly ash? Tl(I) and Tl(III) could theoretically bind to sulfate, nitrate, bicarbonate, etc.. I saw some papers that are using nitrate, sulfate, bicarbonate Tl salt as references for micro-XANES measurement. And then they compared the XANES in the end. Is that a better approach than EXAFS to answer the question?

Well, maybe not "better", but generally tolerant of less good data. And also generally more "directly sensitive" to oxidation state and ligand. I won't kid you though - Hg, Tl, and Pb L3 XANES can be tricky to analyze well, as the features are not very well resolved.

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4. To increase the intensity, we can condense the ash by pressing it into pellet. The fly ash from coal combustion power plants are already pretty compacted. They are mainly gypsum in most cases. I dont' know if that helps or not.

It won't hurt.

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5. This is the first time I heard about non-energy dispersive detector, e.g. PIPS diode. We are planning to use 13-element detector. What is the advantage of using one way or the other? If I do want to concentrate on XANES, would be helpful to ask the beamline engineer for the possibility of changing detectors?

I'd start with the 13-element Ge detector and see how that goes....

Cheers,

--Matt

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-- Mengling Yi Stuckman Graduate Research Assistant Civil and Environmental Engineering and Geodetic Science Ohio State University 2070 Neil Ave., Columbus, OH, 43210