# Recovering Palladium After DMG



## arsenic123 (Nov 5, 2017)

Hey guys, I am working on Palladium refining and after dissolving PD in nitric acid I added DMG and filtered the solution. I now have yellow DMG salt. Now I think its 39% pure because after precipitating PD with DMG we get that much only purity, right? Now I want to make it pure. So what should be next step? 
As per my understanding I can wash the yellow salt with warm water and then re purify it? After washing it with warm water would purity increase to 90%+?

Another step would be dissolving it in Ammonia and then adding HCl to get pure nitric acid. Like the steps in this video. 
https://www.youtube.com/watch?v=btvN9KIghHc

P.S . It was 11 gram of powder which contain 60% PD, 5% PT and some iron and copper. 

Please guide me. 

Thanks


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## 4metals (Nov 5, 2017)

The yellow Palladium salt you collected with DMG is 31.76% Palladium as Palladium dimethyl-glyoxime. So I guess what you are calling purity is the Palladium percentage in the material you have collected. 

You are already at the point of having selectively extracted the Palladium from the mix of metals in your starting alloy, the first major step in making high purity Palladium. 

If your Pd DMG salt is relatively pure refining to high purity is nothing more than dissolving the salt and reducing the metal. Another possibility is calcination, I have never collected Pd-DMG in large enough quantities for calcination to relate to you by first hand experience, the only Pd salt I have calcined was Pd dropped with NaClO3 from aqua regia solutions. 

I typed this from my cell phone so my search function is limited. I believe Lasersteve has posted his method to recover Pd from the yellow salt. If no one else can find and post that link I will be home in a few days and will look for the thread myself.


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## Topher_osAUrus (Nov 5, 2017)

CW Ammen has a great bit on palladium glyoxime, with a few options for your end result.

Take the yellow palladium glyoxime and dissolve it in ammonium hydroxide, which produces a flesh colored solution. (If you suspect the clear solution to be carrying gold or silver ions, add sodium iodide, which will precipitate AuI3 and/or AgI -then filter it off, again leaving a clear solution)

To that clear solution add HCl to precipitate diaminopalladous chloride (called palladium yellow)

There are three ways to reduce the Pd yellow to metallic palladium
1) use hydrazine
2) formic acid
3) calcine

Each one of those has their own pros and cons, and each refiner on their own must decide which will work best for them. Calcining is probably the "safest", since hydrazine has a low flash point and is carcinogenic, same with formic, and it has to be boiling for its reducing step. But, I believe hydrazine will reduce other metals too. Calcining it though, will almost certainly have losses. While formic acid will reduce all of your product with no loss. 
-Im certain all three of those reactions have been covered here on the forum. 

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=8657&p=80997&#p80997
That is the thread I believe 4metals was talking about. 

Good luck, be careful with those platinum sister salts. They'll get'ya !


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## 4metals (Nov 5, 2017)

Thanks for posting that thread Topher,

I noticed the material also has Platinum. A single digestion in aqua regia will allow the OP to recover the platinum as ammonium chloroplatinate and the palladium as palladium(ll) ammonium chloride. Both of which calcine nicely.


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## Topher_osAUrus (Nov 5, 2017)

I cannot recall where I read this bit of information, but I am curious as to its practicality in the calcining operation. Hoping you can shed a little light on it 4metals.

It was mentioned somewhere, that virtually all losses from calcining can be prevented by wrapping the dried pgm material in a lightly damp ashless filter paper, and then proceeding to wrap it again in another filter paper (not wrapped with two simultaneously, but consecutively) omitting the moisture on the second wrapping. After the christmas present wrapping practice, you end up heating the material slowly in the boat, waiting for the paper to flash off. By the time thats happened, the majority of the volatiles will have left, then slowly heating it up the remainder of the way and removing the last bit. 

Allegedly, doing it this way prevents a great deal of the losses... I wish I could remember where I read it exactly, I want to say it was one of Beamish's books, but I sadly cannot recall at the moment.


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## Lino1406 (Nov 5, 2017)

1. To delete Au, Ag with iodide? PdI2 is also a precipitate
2. Melting Pd, not to say its derivative with borax produces flashes - material loss. Borax BP too close to palladium MP


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## 4metals (Nov 6, 2017)

Topher,

If it was in a book by Beamish he is talking about calcining assay quantities, so he is talking fractions of a gram. To my mind, and mind you I may not be the sharpest crayon in the box, adding something that has to burn off invites losses. And if you have a sizeable quantity you will be burning off quite a bit of wrapping papers in the process.

I always liked calcination. The trick, and it is not too difficult, is to ramp up the temperature slowly. The process gives off a dense white fume which is actually ammonium chloride. Corrosive and it blows right through a caustic fume scrubber. When most see the volume of smoke generated they speed up the process and incur losses. 

I always calcined in an electric assay furnace. So first comment I can expect is the coils will not last very long. And that is absolutely correct. But I invested in a quartz glass crucible, one dedicated for each metal I am calcining, and a quartz glass funnel. The salt you are calcining is put in the quartz glass crucible and the quartz glass funnel, (Obviously one that covers the top of the crucible and has a bore of at least 12.5 mm) is inverted over the crucible with the tube extending out of the furnace through the top vent hole. (I always likes Vcella kilns and they have the vent hole in the top center) The fumes generated are now directed out of the kiln and away from the coils. If you want to get fancy because you do this often, you can buy a programmable controller to ramp the temperature up through the heat cycles so you can set it and forget it. 

This method addresses the issue of corrosive fumes on the kiln interior and it allows you to easily ramp up through the temperature ranges slowly allowing for complete reduction. And if done slow enough, the losses are minimal if even detectable. And it's simple and uses equipment in most well equipped labs.


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## arsenic123 (Nov 6, 2017)

Hey guys, thank you for all your inputs. I will first probably go and buy a silica crucible and try to burn/incinerate on our regular cooking gas/stove because I don't have muffle furnace and I will do a XRF and get the pd purity and I will share it with you guys. We can discuss more in details after the report. 

Thank you so much.


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## Topher_osAUrus (Nov 6, 2017)

Thank you 4metals and Lino.

I follow that logic 4metals, and it (calcining) does seem like one of the better methods (if not the best) to getting back your pgms in metallic form. Granted it takes an extra bit of kit. But, better that than cancer or flash fires.

Lino, that was not mentioned in the literature I read, is there another way to separate minute quantities of gold and silver mixed with palladium glyoxime? -It is only mentioned in a couple books, but gold can be reduced by dmg, so I must assume that gold glyoxime (?) Is also soluble in ammonium hydroxide, otherwise Ammen would have just said to filter off the insoluble gold and silver glyoxime salts (? Is that the correct nomenclature?) 

Thanks again gentlemen. Learn something new everyday (thanks to you guys)


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## Lou (Nov 6, 2017)

What is best is entirely dependent on what the end product application is and the customer's requirements. 

Calcination is useful in that it eliminates an aqueous waste stream--the reduction raffinate, which is usually formate or hydrazine-based, both of which need treatment before discharge. 

In any case, it comes down to what you are producing. For fine metal, for instance, one should not calcine palladium in quartz at high temperatures (Pd silicides will form and embrittle the metal such that it cracks on the rolls) and even platinum is risky if reducing conditions prevail, including those introduced from a filter paper! Oddly, porcelain and pyroceram are fine to 600, if not a little risky for thermal shock, but they do not have as marked a formation of cermet (probably from strong metal support interaction: http://pubs.acs.org/doi/abs/10.1021/ar00143a001?journalCode=achre4 )


Unlike 4metals, I have always calcined Pt in air, and put the precipitate in at 900 C and closed the hatch. The ammonium chloride exhaust gas/sublimate can and should be collected and reused for precipitation of more platinum. Pd can be done at lower temperatures with Ar/H2 (5% H2), especially if processing [(NH3)2PdCl2], which is usually made from (NH4)2[PdCl6] anyways. Use of H2 means HCl in the fume and precludes loss due to volatilization. The losses of PGM compounds is due to the formation of metal and, in this case, chlorine gas. Adding something that can turn into CO, like a pyrolyzing filter paper, can make things like Pt(CO)2Cl2 which will volatilize and transport.



As123:
You should melt your Pd after calcining. Take your own melt loss. Unlike Lino's experience, I have induction melted 100 oz lots of recovered Pd from borohydride reductions and though smokey, had no issue with the Pd. Instead I had an issue with multiple crucible failures--so that should be your concern! Borax and silica = borosilicate, much lower softening point!


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## Lino1406 (Nov 6, 2017)

1. Separation of gold, silver from palladium can be done easily prior to DMG
2. DMG-Pd can be considered a Pd separation by itself
3. I read Ammen too, and I think the iodide is questionable. I found more chemical mistakes, but
they are forgivable due to his huge sharing of practical experience


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## Topher_osAUrus (Nov 6, 2017)

Lou and Lino, thank you again. -very much-
Enlightening as usual


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## arsenic123 (Nov 13, 2017)

Ok, so I dissolved PD in nitric acid and added DMG and let it settled overnight and after that I took a silica crucible and burned it on our normal cooking gas for sometime and after that I went to do an XRF report and it was 99.9% pure with 0.1% copper. So it actually became pure and if I melt it it will most probably become 99.99% pure.
Now what I didn't do is I didn't do Denox or removing nitric acid and I directly added DMG and still I got pure PD. So in PD refining removing DMG is not necessary?? I have sulfamic acid but I had forgot to add it to remove excess nitric (My mistake) and still I got pure PD. I will do a stannous chloride test today to see if any PD is there in solution.


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