# recovering pd from nitric containing copper?



## Henk (Mar 30, 2011)

Hi, everyone!
I have read topics on the forum untill my head spins!
I have 15 litres of nitric acid used to recover gold and silver from high grade jewellers filings. I need advice on how to go about recovering the palladium still left in the acid.

Here is the method i used to refign the gold and silver:
1) Melted high grade precious metal filings containing gold, silver, some zinc and some palladium (in the form of 9ct and 18ct white gold filings)
2) Weighed the resuling mixed precious metal bar and added twice the bars weight in copper and melted together
3) Rolled the precious metal containing copper bar to 0.2mm thickness in a jewellers rolling mill and cut to approximately 1.5cm platelets
4) In a deep pyrex dish poured nitric acid over the prepared platelets (approximately 1l nitric acid to 120g of platelets). The concentration of the nitric acid is unknown as i bought it from my local jewellers supply house and the labels on the bottles do not state the acid concentration.
5) After the nitric dissolved the copper completely and the solution cooled i slowly poured the acid into another container leaving the fine gold powder behind. Rinsed the gold powder, dried the powder, added borax and melted in crucible to obtain fine gold ingots.
6) Made a saturated solution of NaCL (table salt) and poured the solution in the left over nitric solution. Silver chloride precipitated and was left to settle for at least 24 hours till the solution cleared. Poured the nitric acid into another container leaving the silver chloride behind. Silver chloride was then treated with NaOH (caustic soda) and concentrated sugar water as per lazersteve's instruction video. The resulting powder was dried, some borax added and melted in a crucible to obtain fine silver ingots.
7) What now? :? 

I read on the forum that ammonium chloride can be used to get palladium out of nitric solution and i was able to obtain 1kg of ammonium chloride. 
I need some help on the best method to proceed to extract the palladium from the appoximately 15 litres of nitric acid that i have. Any help appreciated!


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## Oz (Mar 30, 2011)

If you have all of your silver removed you could cement your palladium on copper.


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## Henk (Mar 30, 2011)

How do you cement the palladium onto copper? 
Please excuse my ignorence/lack of knowlege


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## etack (Mar 30, 2011)

put copper in nitric solution :lol: 

use a bar or sheet not wire or powered less copper contamination

Eric


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## Henk (Mar 30, 2011)

Each litre of nitric already contains approximately 80 to 90 grams of copper from the refigning process that i used. any idea how much extra copper i would have to add? 
Does the term cementing have the same meaning as precipitation?


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## samuel-a (Mar 30, 2011)

Henk said:


> Does the term cementing have the same meaning as precipitation?



Sort of... Cementing is one kind of precipitating.
You replace less reactive metals with a more reactive one, the metals that comes out of solution, does so on the surface of the more reactive metal (like cement)



Henk said:


> Each litre of nitric already contains approximately 80 to 90 grams of copper from the refigning process that i used. any idea how much extra copper i would have to add?



No need for calculations here, just hang a piece of solid copper (buss bar or pipe) in the solution and let it stand for few days. If any black powder forms onto the copper, this will be your 'cemented' PGM's.
Collect them and sell or process your self.

Good luck.
Sam


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## Henk (Mar 31, 2011)

Thanks for clarifying Sam.
Would it be possible to heat the nitric solution below boiling point for water to evaporate and eventually have the palladium precipitate out of solution?


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## samuel-a (Mar 31, 2011)

Your welcome Henk



Henk said:


> Would it be possible to heat the nitric solution below boiling point for water to evaporate and eventually have the palladium precipitate out of solution?



It doesn't really work that way... this action will basically make your solution saturated with... whatever is in that solution, that's including zinc, copper, nickel, palladium platinum or whatever is in there... and they will be pushed out stu as nitrate compounds rather the elemental metal...

My best advice to you is to keep going on your reading here on the forum, most of the info is here.
take a look at Steve's website and in mine own website to and see tutorials and guides.

Best of luck to ya
Sam


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## 4metals (Mar 31, 2011)

Henk,

At this point I think your only option is to cement the palladium. I can't help but notice that you are calling the gold from this inquarting and leaching process fine gold. While it may exceed 99% fine it needs to be processed in aqua regia to achieve the purity usually associated with fine gold (.9995) It may be good enough to sell as you recover it from the parting process and if it is it is not worth changing unless your sell price is substantially discounted.

You also refer to the silver from the conversion of the chlorides as fine silver. It too is not much over .99 fine. 

You mention obtaining nitric acid from a Jewelers supply. If that is the case I'm sure it is not cheap. You might consider in the future inquarting with silver (as you accumulate it from the lots you process) because the silver will use 1/3 of the acid used to remove the copper. That acid can be cemented to recover any gold, silver and palladium as a melt-able metal, skipping the chloride step entirely. Processing in a small silver cell will yield .999 silver, and leave any gold in the slimes and concentrate the palladium in the solution where it can be recovered when it builds to high enough levels to contaminate the cell. When it is time to recover the Palladium, there are methods posted on the forum for recovering palladium from a nitric solution.


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## Henk (Mar 31, 2011)

Thanks for the info guys. Very helpfull!
I have found a new nitric supplier that sells very concentrated nitric acid at half the price of the jewellery supplier. It is so concentrated i have to add nearly 2 litres of water to each litre of nitric for it to work properly.
The purity of the gold that i recover is adequite, as i sell it to a long time friend of mine that assays the metal and pays me spot price!  

Inquarting with silver sounds like a great idea! I have never tried it this way, sounds much cleaner. Next time :lol: 
Also i like the idea of using a silver cell to recover the silver and leave the gold behind in a sludge, then recover the palladium at a later stage.


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## goldenchild (Mar 31, 2011)

Oz said:


> If you have all of your silver removed you could cement your palladium on copper.



Oz,

What if your Ag _isnt_ separated from your Pd? Would the best way of going about recovering the Pd(short of DMG) be to cement the Ag and Pd out and then dissolve the Pd in HCL?


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## samuel-a (Mar 31, 2011)

Mario, you can cement the Pd /Pt with a slab of silver, prior to Ag cementation. Use heat to hasten the process.


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## goldenchild (Mar 31, 2011)

Aaaah. Didnt think of that. Silver is above Pd. Thanks Samuel.


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## Oz (Mar 31, 2011)

Goldenchild,
If you still have silver in your solution you would get a cement that is both silver and palladium mixed. Since the silver was being removed with a chloride in this case it only makes sense to be sure you have completed that process before cementing out your palladium so you will have cleaner products of both elements.

Samual-a,
I know that in looking at the electromotive series of elements that it seems silver will work to cement out Pd, but in reality it is not practical since they are too close together electromotively. Don’t take my word for it though, you have some palladium you can put into solution and try cementing with silver. After your palladium has been cementing on silver for a week, add some DMG and see how effective your cementation was.


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## samuel-a (Mar 31, 2011)

Oz,

Your point is good. I thought about it as well and did expirimented with it.
I heated the nitric leach with a silver slab until no more cmenting occured, at that point i took a samle and precipitated the silver with HCL and tested with SnCl. The test showed negative for PM's.

The black precipitates dissolved with AR and tested positive both for Pt and Pd.


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## Oz (Mar 31, 2011)

Well I have to say I never tried driving that reaction with heat. 

Some things to consider; 
If you precipitated your silver as the chloride from your nitric with HCl you would be left with a high nitric AR. It is very hard to get accurate SnCl tests in that solution to be sure of a negative result. 

It seems you have had at least limited success with this by using heat, but it is worth noting that it requires 3 times more silver than it would if using copper to cement a nitric solution. Copper completes the reaction timely without the need for heat and removes all values instead of leaving silver in the solution.

I just might have to try what you did some day using heat to drive the reaction. But I can’t think of a circumstance where I would want to use silver this way other than intellectual curiosity.


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## samuel-a (Mar 31, 2011)

Oz 

Again, good points.
I feel that i most try the testing with DMG rather then SnCl.
Or maybe some of the more expirenced moderators / members could chim in the debate and tell if cementation with silver can reslt in 100% cementation of Pd..

I personally incorporeted this step to all of my nitric leaches, at the moment it does not create silver shortage for me. I collect the black powder tp be refined later.


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## samuel-a (Apr 3, 2011)

Update:

Well Oz, I have tried your suggestion.

I dissolved in 35% nitric acid a small (0.1g) BB of Pd, which i assume to be at least 99% pure.

Then introduced silver to the solution and brought to boil. After a minute or so, some black powder did cemented, but the solution remained orange, more silver was added, even when it reached saturation point of silver, there was no more cementation going on. No need for testing, it is clearly visible no cementation occurred and no more Pd pushed out of stu. 

So i guess you were right, i can not reach 100% recovery of the Pd from nitric using silver, and therefor not worth doing so, just cement with Cu and part in Ag cell and treat the slimes.

Maybe the copper presence in my previous attempts helped pushing out more Pd on to the silver... :?:


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## goldenchild (Apr 3, 2011)

Ok so cementing Pd out with Ag doesn't seem to be very effective. So my question still stands. Could the silver and Pd be cemented out with Cu and then the Pd digested with HCL? I know Oz responded to this question but I wasn't 100% clear on the answer. 

Also, if you had an Ag/Pd nitric solution, could you just add HCL to drop the Ag as a chloride and then filter the solution to get the Pd (cement with copper, sodium chlorate, bleach)?


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## samuel-a (Apr 3, 2011)

goldenchild said:


> Ok so cementing Pd out with Ag doesn't seem to be very effective. So my question still stands. Could the silver and Pd be cemented out with Cu and then the Pd digested with HCL? I know Oz responded to this question but I wasn't 100% clear on the answer.



I'm afraid this will not be my first choice nor the secund.... Although Pd will partially dissolve in hot HCL, to dissolve 100% of Pd you will need heat and probably some oxidizer (H2O2, Cl, Nitric), this essentially will form chlorides of silver as well as large volume of solution with very little Pd in it, which later needs to be concentrated for the recovery of Pd.



goldenchild said:


> Also, if you had an Ag/Pd nitric solution, could you just add HCL to drop the Ag as a chloride and then filter the solution to get the Pd (cement with copper, sodium chlorate, bleach)?



I've done so in the past with success, though dealing with AgCl later is not so fun for me .

p.s - In my experience I've come to learn that AgCl, when precipitated do tend to trap some other dissolved and/or colloidal elements with it at minute proportions (such as copper, nickel, gold, palladium, platinum etc...)


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## Oz (Apr 4, 2011)

Goldenchild,
I agree with samuel-a that cementing both on copper then trying to remove the Pd with HCl is the wrong way to go. 

If you have Ag and Pd digested in nitric I would typically suggest removing the silver as a chloride then cementing the Pd on copper. I say typically, only because if you are only talking small traces of Pd it may be more cost effective to remove the Pd with DMG, then cement the silver on copper in order to avoid the hassle of silver chloride. 

I hope this time my answer made sense.


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## Oz (Apr 4, 2011)

Samuel,
Thanks for testing that with a known quantity of Pd at a boil. Like I said, I was rather sure but had not tried heat.


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## samuel-a (Apr 8, 2011)

well... actually i should thank you for provoking me to further pursue this subject.

To further prove your claim, i took some snap shots :
left - Pd Nitrate saturated with Ag. Center+Right - HCL addition and AgCl precipitation.


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## Oz (Apr 8, 2011)

Nice to see you testing. You will need to wash your silver chloride several times in order to remove the bulk of the Pd nitrate that is trapped in it. Silver chloride is terribly good at drag down contamination.


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## samuel-a (Apr 8, 2011)

Oz said:


> Silver chloride is terribly good at drag down contamination.



Yup...


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## goldenchild (Apr 8, 2011)

This is exactly how I pictured this technique playing out. I dont mind dealing with AgCl so thats why I suggested it. I think vaccum filtration would be best in this case. Not #5 or even #2 paper though!


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## kjavanb123 (Apr 12, 2018)

Hi

Followed the advise in this thread and for the first time I tried to precipitate palladium from a copper nitrate solution.

I had a nitrate solution mostly copper and trace of palladium, so I dropped a 204 gram copper ingot into the solution after 24 hrs, there are some black fines stuck to the copper ingot as can be seen below,

Copper before cementation,



Copper after 24 hrs into nitrate solution with mostly copper with small amount of Pd.



Now the question is how one removes the black powder which seems to be stuck to copper ingot.

Best regards
KJ


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## 4metals (Apr 12, 2018)

In low concentrations and nitric based solutions have you considered DMG?


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## kjavanb123 (Apr 12, 2018)

4metals,

I have already know about the DMG usage, a I have used that to precipitate Pd from nitrante solution.

This is my first trial with plating on copper, hence this experiment.

I forgot to weigh the copper ingot before putting it in the nitrate solution, so by weighing it now I can estimate the Pd amount.

Best regards
KJ


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## FrugalRefiner (Apr 12, 2018)

kjavanb123 said:


> I forgot to weigh the copper ingot before putting it in the nitrate solution, so by weighing it now I can estimate the Pd amount.


That wouldn't have helped. In cementation, copper dissolves into the solution to replace the palladium (and any other metals below copper in the reactivity series), so the copper would lose weight in the reaction. You also wouldn't know how much copper was simply dissolved by any excess nitric.

Dave


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## nickvc (Apr 12, 2018)

Kevin when using copper to cement PGMs it helps to have agitation, a bubbler will do, and to use a large surface area of copper high cements the PGMs more fully and quicker, to recover the palladium or any other PGM I’d use a cell to concentrate the values which makes recovery easier.


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## kurtak (Apr 13, 2018)

nickvc said:


> Kevin when using copper to cement PGMs it helps to have agitation, a bubbler will do, and to use a large surface area of copper high cements the PGMs more fully and quicker, to recover the palladium or any other PGM I’d use a cell to concentrate the values which makes recovery easier.



Correct - using a bubbler will also "help" to prevent the PGMs from adhering to the copper which can in turn cause a "passivation" layer of PGMs on the copper which in turn can prevent the PGMs from completely cementing out of the solution 

Kurt


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