PGM recovery diff method.

[nickvc]

Having just reread this thread to try and get some understanding of the processes to achieve a fairly pure product I have to agree with Lou,s assessment that refining the PGMs is much more involved and difficult than dealing with gold and silver hence my decision not to try, leave it to those that can and safely. My problem is not unique I have a batch of PGMs in solution from the stock pot and really don't want to refine each but just recover as a mixed precipitate. I tried cementation but find the powders adhere quite tenaciously to the copper bar so I was wondering if using fine copper powder would work, I'm not bothered if it's totally PGMs but I don't want to melt small amounts of PGMs with large amounts of copper to recover the values hence the reason I don't want to use zinc. If anyone has any better ideas I would be pleased to hear them so I can put this to bed and free up my beaker.

 

[HAuCl4]

Having just reread this thread to try and get some understanding of the processes to achieve a fairly pure product I have to agree with Lou,s assessment that refining the PGMs is much more involved and difficult than dealing with gold and silver hence my decision not to try, leave it to those that can and safely. My problem is not unique I have a batch of PGMs in solution from the stock pot and really don't want to refine each but just recover as a mixed precipitate. I tried cementation but find the powders adhere quite tenaciously to the copper bar so I was wondering if using fine copper powder would work, I'm not bothered if it's totally PGMs but I don't want to melt small amounts of PGMs with large amounts of copper to recover the values hence the reason I don't want to use zinc. If anyone has any better ideas I would be pleased to hear them so I can put this to bed and free up my beaker.

1-Evaporate stock pot to a crust, mix well with litharge and flour/powdered coal, and cupel?. (Add a little silver, silver oxide, or AgCl to help collect into a button free of base metals.)

2-Alternatively, you could use concentrated sodium formate in slightly acid (formic acid) solution to precipitate all precious metal blacks together after you concentrate the stock pot. The settling is a pain to watch. The blacks are a pain to handle, but they are really ready for further processing.

3-Or... use thin copper foil sparingly to cement.

edit: I'd choose number 3 in 99.99% of cases. :lol:

 

[HAuCl4]

refining the PGMs is much more involved and difficult than dealing with gold and silver.

The main difficulty is in getting them in enough quantities. Everything is done in 8 hours or less these days for all 8 metals. Coming soon to a kitchen near you!. Rhodium is a ***** though.

 

[goldenchild]

Specifically though, it is indeed a weird phenomenon.

Agreed. I believe it was Harold who I saw mention this oddity. I thought he had misspoke but he enforced and clarified.

Platinum... the goofball of PMs :lol:

 

[freechemist]

Hey Lou,

Your statement "you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough." is perfectly right, as is your foregoing statement: "Halogen and HCl with pressure and heat in a Pfaulder is the way to go".
In my last post I spoke definitely only of relatively fine powder, like platinum-black, which dissolves after my experience much faster, if the dissolving acid contains some HBr, too. In my practice I found that addition of some HBr is also very effective in the dissolution of coarser grey, evidently metallic Pt-powders, like they are obtained by reduction of platinum-solutions with hydrazine sulfate or with formic acid/formiate in a strictly controlled buffered system at a pH-value around 2. What concerns the dissolution reactor, I preferred always a massive titanium-reactor over a Pfaudler for all operations with corrosive PM-solutions.
Your third statement "Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does" I can partly confirm, too, except, that I preferred copper as alloying metal and a total Pt-content of about 80%. This receipe functions well, even for Pt alloyed with Ir or Rh.
I am sorry, that I can not confirm your last statement: "Today, all the real platinum refining is done with s/x and runs through pretty little tubes. I think freechemist was at MetalorSA in Switzerland, so I'm sure he can confirm", because I never was employed by Métalor.

@Dr. Poe:

There is one simple, but very effective way, to avoid formation of sparingly soluble Ag2PtCl6 on adding HCl to a combined solution of Ag and Pt in HNO3. You just have to reverse the addition, that means, you add the silver and platinum containing nitric acid solution to a well stirred bulk of a great excess of hydrochloric acid. Thus precipitation of practically insoluble AgCl occurs immediately, whereas the formation of the complex anion PtCl6(2-) affords much more time.

Regards, freechemist

 

[Dr. Poe]

Hey Lou,

Your statement "you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough." is perfectly right, as is your foregoing statement: "Halogen and HCl with pressure and heat in a Pfaulder is the way to go".
In my last post I spoke definitely only of relatively fine powder, like platinum-black, which dissolves after my experience much faster, if the dissolving acid contains some HBr, too. In my practice I found that addition of some HBr is also very effective in the dissolution of coarser grey, evidently metallic Pt-powders, like they are obtained by reduction of platinum-solutions with hydrazine sulfate or with formic acid/formiate in a strictly controlled buffered system at a pH-value around 2. What concerns the dissolution reactor, I preferred always a massive titanium-reactor over a Pfaudler for all operations with corrosive PM-solutions.
Your third statement "Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does" I can partly confirm, too, except, that I preferred copper as alloying metal and a total Pt-content of about 80%. This receipe functions well, even for Pt alloyed with Ir or Rh.
I am sorry, that I can not confirm your last statement: "Today, all the real platinum refining is done with s/x and runs through pretty little tubes. I think freechemist was at MetalorSA in Switzerland, so I'm sure he can confirm", because I never was employed by Métalor.

@Dr. Poe:

There is one simple, but very effective way, to avoid formation of sparingly soluble Ag2PtCl6 on adding HCl to a combined solution of Ag and Pt in HNO3. You just have to reverse the addition, that means, you add the silver and platinum containing nitric acid solution to a well stirred bulk of a great excess of hydrochloric acid. Thus precipitation of practically insoluble AgCl occurs immediately, whereas the formation of the complex anion PtCl6(2-) affords much more time.

Regards, freechemist

Sounds reasonable, I'll try that myself. Dr. Poe

 

[Dr. Poe]

refining the PGMs is much more involved and difficult than dealing with gold and silver.

The main difficulty is in getting them in enough quantities. Everything is done in 8 hours or less these days for all 8 metals. Coming soon to a kitchen near you!. Rhodium is a ***** though.

I usually smack that b'''ch with sulfanyl chloride in solution or with sodium bi-sulfate in a melt. Dr. Poe

 

[HAuCl4]

Dissolving it (rhodium) is trivial. Ridding it of impurities isn't. :shock:

 

[Dr. Poe]

Dissolving it (rhodium) is trivial. Ridding it of impurities isn't. :shock:

Quite so!,, One takes advantage of the trichloride's insolubility in ether. 8) Dr. Poe

 

[butcher]

Raleigh Gilchrist and Edward Wichers wrote an article, titled

A Procedure for the Separation of the Six Platinum Metals from One Another and for their Gravimetric Determination.
1934-1935, publication national bureau of standards of U.S. Department of Commerce.

Here they use a different method of separation, than is normally done, it sounds like a method that produces or separates these metals from each other in high quality (less mix of the PGM metals, and the metal separation more complete).
Osmium and Ruthenium are distilled, (note these can be dangerous as gases),
Their paper describes the distilling rig and absorption flasks, and reagents needed for the procedure.

The paper also describes the separation of platinum, Rhodium palladium and Iridium.

It is a very interesting article even if you never tried the procedures described, it also give clues to some of the problems we encounter with conventional methods of separation of these metals.

 

[HAuCl4]

Raleigh Gilchrist and Edward Wichers wrote an article, titled

A Procedure for the Separation of the Six Platinum Metals from One Another and for their Gravimetric Determination.
1934-1935, publication national bureau of standards of U.S. Department of Commerce.

Here they use a different method of separation, than is normally done, it sounds like a method that produces or separates these metals from each other in high quality (less mix of the PGM metals, and the metal separation more complete).
Osmium and Ruthenium are distilled, (note these can be dangerous as gases),
Their paper describes the distilling rig and absorption flasks, and reagents needed for the procedure.

The paper also describes the separation of platinum, Rhodium palladium and Iridium.

It is a very interesting article even if you never tried the procedures described, it also give clues to some of the problems we encounter with conventional methods of separation of these metals.

Lou kindly posted that article in this thread below, and gave some other tips:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=11599&p=113821&hilit=cupferron#p113821

It is an analytical procedure, but many of the procedures can be adapted to the larger scale refining. Others, like the use of DMG for palladium, and titanous chloride for Rh/Ir separation aren't practical in large scale, but used as scavengers work great. (To scavenge traces of palladium with DMG, or traces of rhodium in nearly pure iridium solution with titanous chloride-cupferron).

In one refinery I visited, they routinely separated the metals to 99%+ , and then proceeded to re-refine them / purify them in several steps, that went relatively quickly, with routine lab equipment. The alloys of platinum are usually binary, so that helps a lot. It is rare to have more than 3 together, unless one melts them together. :shock:

Even ruthenium can be separated without distillation. That's handy because it is common as a platinum hardener.

Here's a summary of Raleigh Gilchrist's papers and life. A crash course in PGMs if there could be such thing. :lol:

 

[g_axelsson]

This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.

Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!

By the way... is there a palladium analog to Ag₂PtCl₆? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s.

Göran

 

[9kuuby9]

This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.

Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!

By the way... is there a palladium analog to Ag₂PtCl₆? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s.

Göran

Precipitate Ag with HCl as AgCl (to avoid this "Ag₂PtCl₆?" complex) let is settle then decant most of the solution and filter that last bit of solution with the AgCl together with the decanted solution. keep washing your AgCl until the solution becomes colorless and add the solution for filtering.

Ad more HCl to your Pd(NO3)2 solution along with heat and lots of stirring to convert it to PdCl2. (doubling the solution with HCl should suffice; any extra HCl will be used to Denoxx the solution afterwards)

denoxx the solution from NO2 (converting Ag to AgCl creates additional HNO3); then evaporate (with heat around 50C° and also some stirring) the solution down to 15ml to 20ml of solution per gram of Pd (average MLCC's yield max around 0.3% of Pd per gram of MLCC's) Then double the solution with HCl; then evaporate and repeat it for 3 times. Then evaporate it back to 15ml to 20ml of solution per gram of Pd. Now your solution is ready; for further selectively separating the Pd from the solution.

 

[g_axelsson]

This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.

Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!

By the way... is there a palladium analog to Ag₂PtCl₆? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s.

Göran

Precipitate Ag with HCl as AgCl (to avoid this "Ag₂PtCl₆?" complex) let is settle then decant most of the solution and filter that last bit of solution with the AgCl together with the decanted solution. keep washing your AgCl until the solution becomes colorless and add the solution for filtering.

Add more HCl to your Pd(NO3)2 solution along with heat and lots of stirring to convert it to PdCl2. (doubling the solution with HCl should suffice; any extra HCl will be used to Denox the solution afterwards)

denox the solution from NO2 (converting Ag to AgCl creates additional HNO3); then evaporate (with heat around 50C° and also some stirring) the solution down to 15ml to 20ml of solution per gram of Pd (average MLCC's yield max around 0.3% of Pd per gram of MLCC's) Then double the solution with HCl; then evaporate and repeat it for 3 times. Then evaporate it back to 15ml to 20ml of solution per gram of Pd. Now your solution is ready; for further selectively separating the Pd from the solution.

Thanks, I read about another trick (from freechemist) in avoiding creating the Ag₂PtCl₆ by pouring the silver - platinum nitrate into HCl. But that is still for dealing with platinum solutions. The solution from MLCC:s is silver - palladium based.
I made some searches and I could find many references to Ag₂PtCl₆ but no substance based on palladium instead of platinum. I haven't read up on PGM chemistry yet so I was wondering if there could be a similar compound created when I tried to denox my solution. I think I evaporated it too far and the next time I'll try your recommendations instead.
I tried to drop any silver before denoxing by adding NaCl but I didn't get any precipitate so I probably don't have any silver after all. I'm going to do some experiments with the precipitate to see if I can get it into solution again and find out what it is made of.

Göran

 

[Richard NL]

January 31st, 2012, 5:14 am

For those who are interested in a historical work:
http://books.google.com/books?hl=en&lr=&id=sok6AAAAMAAJ&oi=fnd&pg=PA7&ots=rZIrRnk-By&sig=bhq86Xr73VX9V6OpiJj22D6qlUc#v=onepage&q&f=false

Complete book:
https://www.docdroid.net/QxkICxV/the-chemistry-of-ruthenium-rhodium-palladium-osmium-iridium-and-platinum.pdf

Regards,