wildrebe
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get RHODIUM out of glassware
Hi, I am using a heterogeneous rhodium catalyst for my experiments. There is still catalytic activity left after washing in a lab washing machine
(acidic and neutralizing step). To get the rhodium out, I also tried:
- aqua regia
- concentrated sulfuric acid
- sulfuric acid with NaCl
- base bath
Nothing really worked. What else can I try? How about :
- NaCl through which Cl-gas is bubbled?
- sodium bisulfate?
Thanks for suggestions!
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Bot0nist
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I would say the extended washes with warm aqua regia would be the best bet. You will probably just have to give it some time for the acid to work.
Maybe change out the acid for fresh a few time.
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madscientist
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From Cotton's 6th edition of "Advanced Inorganic Chemistry":
| Quote: | | Rhodium and Ir are extremely resistant to attack by acids, neither metal dissolving even in aqua regia when in the massive state. Finely divided Rh
can be dissolved in aqua regia or hot concentrated H<sub>2</sub>SO<sub>4</sub>. Both metals also dissolve in concentrated HCl
under pressure of oxygen or in presence of sodium chlorate in a sealed tube at 125-150C. At red heat interaction with Cl<sub>2</sub> leads
to the trichlorides. |
What was your catalyst? What reagents were used? More information may help us devise a solution.
I weep at the sight of flaming acetic anhydride.
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wildrebe
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The catalyst is rhodium on powdered aluminia, my experiments are in water, reagents are 100uM of organic (bromated) compounds. I am only using about
1mg of Rh per L, so the Rh residues in the glass bottles are rather small. I was hoping to get the rhodium out with a solution not too expensive and
not too time consuming, as I would be using (and cleaning) 2 bottles per day..
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DJF90
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You might want to try hypochlorite bleach?
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hkparker
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Exactly what I would say. NurdRage did a video about how Ruthenium would only dissolve in bleach (not even hot conc. aqua regia), so rhodium might be
the same.
http://www.youtube.com/watch?v=H7Ng4sOVkns
My YouTube Channel
"Nothing is too wonderful to be true if it be consistent with the laws of nature." -Michael Faraday
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Fleaker
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Bleach will not work.
Madscientist basically gave you your options.
Rhodium black and rhodium sponge both dissolve in aqua regia but it should be hot ~80C. I've recovered rhodium off its alumina support before using
aqua regia, and using SO2/Cl2 in a quartz tube c. 850 C.
You must use refluxing sulfuric acid to dissolve it--this is what I use when preparing it for making a plating solution, or when I refine it. If
you're not seeing white fumes, you're not hot enough. It will go brown when it begins to dissolve (presuming no organic matter remains, but even then,
that will be oxidized by the hot sulfuric). It goes to a red solution in aqua regia.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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wildrebe
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thanks fleaker, you were right, bleach does not work. I'll try hot aqua regia. Can I reuse the aqua regia a couple of times or is the reaction
finished when it has turned red?
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Fleaker
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Well, aqua regia turns red-orange on standing anyway due to the NOx produced as the NOCl decomposes...
I suppose you could also just wet the glass with water then sprinkle NaHSO4 on it. Heat that very hot until it forms pyrosulfate and it'll dissolve
the rhodium giving a deep red color (hence the "rhod" of rhodium)
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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