Mixed Black PGM Powders

Any questions about other precious metals.
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ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 20th, 2018, 12:26 am

i am posting about a problem with black pgm. now i clear it more so someone can help me out! i got black pgm leached with hcl/cl and use zinc to get pgms. treated with nitric for pd. later i use hcl/peroxide to dissolve pt. now i have some powder not dissolving any more in hcl/peroxide, even nothing happen in h2so4! what i should do next?
image.jpg
look its color which is not completely black. its bluesh type . any help please
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Platdigger
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Re: Mixed Black PGM Powders

Post by Platdigger » August 20th, 2018, 2:53 am

What is the source of your zinc?

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 20th, 2018, 3:22 am

its spareparts of bikes and vhicles! melt them and get the melted zinc! in long pieces!

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 20th, 2018, 12:15 pm

thanks platdigge! i got one more mistake, i try on whole bunch , not a sample of remaining unknown powder! well here is the pic of zinc that i use
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jimdoc
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Re: Mixed Black PGM Powders

Post by jimdoc » August 20th, 2018, 12:20 pm

Zinc from "spareparts of bikes and vehicles" can be unknown alloys that add impurities.

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 20th, 2018, 1:27 pm

ok . i already guess as i read kadrive post about cab-o-sil in zinc. but i am still assure i do not get 40 gram impurities in 60 gram powder! is there any way to find out if it is impure zinc substances or something else?

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 20th, 2018, 1:33 pm

is ther any way to find pure zinc? here in pakistan ,zinc sheets are not available, as a zinc source i also use toys,door handels, some mobile bodies, dry cell covers, but main source is vhicle parts and here is a pic of impurities i seprate by melting zinc
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Lino1406
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Re: Mixed Black PGM Powders

Post by Lino1406 » August 20th, 2018, 10:47 pm

Use aluminum sheets (if you don't have too much nitric). You may need to brush them from time to time. Also raise pH = 3

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 21st, 2018, 12:46 pm

thanks for reply! is aluminium fine to percipitate pgms? as i read on this forum that pgm black with aluminium can cause trouble. i will try to find thread, and also i not use nitric. i use hcl/cl leach mathod, ?

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 21st, 2018, 12:56 pm

Lou
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PostNovember 6th, 2008, 7:37 pm

I'll give you the short answer:

In this case, Hoke is wrong. Aluminum is inconvenient to use because it is tough contaminant to remove because it forms sticky gels (like what tin does with conc. nitric, metastannic acid goo!).

To understand why it is such a royal pain, you must know something of its aqueous chemistry.

When you go to do a cementation reaction, you are basically using a reactive metal to displace a less reactive metal. That much you know. When the aluminum or zinc goes into an acidic solution, it produces hydrogen gas. It is both the nascent (new-born) hydrogen that does the actual reduction of these metals and the chemical potential caused by the flow of electrons. Gross simplification here.

The problem with aluminum is that it has problematic aqueous chemistry and can do several things. When you put aluminum metal into this hydrochloric acid solution, you get "aluminum chloride hexahydrate" (not really, actually it is a mixture of many things: [Al(H2O)6]3+ + H2O --><-- [Al(OH)(H2O)5]2+ + H3O+, and also the benign complex AlCl4-). In short, this is hydrolysis. This is driven by the low Ksp of hydrous aluminum oxide, Al(OH)3. Now you may ask, why am I getting a seemingly basic precipitate (note the OH function in it) when I am doing a reduction at low pH in hydrochloric acid? Well, alumina is called an acidic oxide for this reason, it precipitates at low pH! Recall that water autoionizes into both hydronium (H3O+) and hydroxyl (OH-) ions. This is because water is amphoteric and acts as both an acid and a base. Well, as luck would have it, so do many other things, in particular aluminum hydroxide. The hydroxyls from water's autoionization will hook up with any AlCl4- and any hexaaqualuminum (III) floating about (which is what happens when aluminum cation is present with excess water from HCl).

So what does this mean in practical talk? It means that even at low pH of around 1 (which is equivalent to 1M HCl) you will have some aluminum hydroxide beginning to drop out because of hydrolysis. I think the actual math (which gets nasty if solved exactly, 8 or 9 unknowns) says it starts at pH 1.4. Anyhow, this gets entrained and mixed up with your cemented values and becomes hell to remove. It requires a boil in base (to complex the aluminum hydroxide as soluble aluminate, Al(OH)4-) or in a very conc. solution of HCl. Aluminum hydroxide forms alumina upon heating, a very stable entity--it is used as refractory for lining steel ladles or as an abrasive, or in sapphires in rings.

Did I also mention that this aluminum hydroxide is very flocculent and slimy and will clog filters? It is a pain to remove from your metals. Pure Al(OH)3 made by an analytical chemist with good technique and know how won't do this, but I can guarantee you, it will when you try it. Not trying to insult, but there is a lot of math, technique, and art to it. It ties in with selective precipitation techniques, also a good tool for refining! I'd be willing to discuss this all in more detail with math and examples if there is enough interest...

ashir
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Re: Mixed Black PGM Powders

Post by ashir » August 27th, 2018, 9:45 am

last time seperating pgms from black powder stuck. got 10 gram palladium by nitric/dmg . later alot back yellowish powder was hard to dissolve in any acid/ AR, at any temp! so i got more 200 gram black pgm. i want saperate pgms by bisulfite fusion. can any one guide this process or any link?

Raza shahid
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Re: Mixed Black PGM Powders

Post by Raza shahid » November 10th, 2018, 6:18 pm

Hi kad river you done great job my friend, u r active member here, my friend i need some help of yours to get pdcl2 brown powder or brown salt i have refined pd salt from mlcc and at the end of chlorination process i got some yellow salt may be ammoniumhexachloropalladate, but i need pdcl2 can u please help to achieve this i think calcing process can evolve ammonium chloride to get pure pdcl2. But i may be wrong i need to know the right way, it will be appreciated.

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FrugalRefiner
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Re: Mixed Black PGM Powders

Post by FrugalRefiner » November 11th, 2018, 8:00 am

Raza shahid, please do not use text lingo like "u r" here. Many members have to use translators, and things like that do not translate well.

Dave
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