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

Matt Newville newville at cars.uchicago.edu
Thu Sep 29 19:00:31 CDT 2011

Hi Mengling,

2011/9/29 Mengling Yi Stuckman <stuckman.12 at osu.edu>:
> 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.


> 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.


> 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.

> 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.

> 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....



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