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Author: Subject: Strange sulfite
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[*] posted on 27-4-2013 at 20:26
Strange sulfite

As many may have experienced with, dealing with PGM metals specially when isolating them from other contaminants is a total pain in the ass even specially when extracting it from amtrixes like a ceramic honeycomb automotive catalyst...
Okay, here is the deal,
The composition of the matrix is supposed to be a mixed alumina-silicate type, so most solubles would be according to a table in the attach.:
Platinum 800 - 1050 [ppm]
Palladium 0
Rhodium 50 - 60 [ppm]
Aluminum 6.5 - 9 [t]
Lead 1.2 - 2.0 [t]
Iron 0.7 - 0.9 [%]

200g of this were poured along 1L 33% HCl and the matrix didn't seem to react even at 70deg. Addition of hydrogen peroxide released caracteristic bubbling oxygen gas, but I can't know if thats iron decomposing all the H2O2, or Pb2+ being oxydised to Pb4+ or barium or aluminium going throug the solution. Well there was this relatively massive precipitate probably comprised of 5g lead/ barium/ sulfites.
That shouldn't be iron as a test with FeSO4/ Fe2(SO4)3 both showed strong coloring of the solution upon exposure to sodium metabisulfite, but the actual extract actually decolorized when the metabissulfite was added.
A source states lead sulfite as an insoluble salt at room temp, neverthless its solubility rapidly rises with temperature reaching several grams per liter at 100deg!!
Also, another source states that all sulfites are readily soluble in acidic media...
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[*] posted on 28-4-2013 at 05:04

Recovery of precious metals from automotive exhaust catalysts has been covered several times here. UTSF.

To dissolve the Pt/Rh, you'll need Aqua Regia but this shouldn't affect the ceramic matrix much.

As the salts of a weakish acid, sulphites are probably all soluble in solutions of low pH, through acid displacement.

I'm not sure in this case but e-gold diggers often recommend neutralising the excess nitric acid with urea, prior to treatment with metabisulphite to precipitate the precious metals.

[Edited on 28-4-2013 by blogfast25]

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[*] posted on 28-4-2013 at 19:59

Im inclined to believe.. that it IS PGM metals out there, just in a very fluffy olated form.
The same happened when I extracted the very last bit of PGM out of computer parts. It turned out a greyish silvery powder similar to elemental silver when it just comes out of a sugar batch. The exposition time, pH gives an ammount that H2O2 should have dealed with.
I'll repeat the test with that supposed PGM I got, see if it dissolves with hydrochloric acid. If yes, that was sulfite s**t, if not, wow, we have a big deal.
Ah, sorry, I didn't attach that document. Sorry if it was attached somewhere else.
PS.: sorry, the file is too big. Please search for Platinum and Rhodium Recovery from Scrapped Automotive
Catalyst by Oxidative Acid Chloride Leaching and you should pretty much succed. Thank you.

Do you think of any niche uses for the platinum the way it is? I think atomized metal strongly interacts with water and even ions, forming an amorphous mass of unknown composition... Yea.. I think it is PGM.. like for last time I got half a beaker of it and thought I was ther richest genius on earth.
It is like looking at an atomic cloud... wow.. just wow dude....

[Edited on 29-4-2013 by platedish29]
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