I'm having trouble cementing Palladium, help...

[fabriciomnarvaez]

Good afternoon everyone, greetings... I had a Nitric solution, with Palladium and Nickel, I went to try to cement the PD with CU, and the Nitric dissolved the CU and didn't cement the PD, now I have a PD, CU and NI solution. How do I recover only Palladium? Another thing, when I cement another solution with PD, do I have to stabilize the Nitric Acid with Sulfamic acid or urea? and how long do I leave the copper bar cementing in the solution?

 

[lazersteve]

How much Pd do you suspect is in the solution?

 

[fabriciomnarvaez]

I suspect it has between 0.6g to 1g

 

[lazersteve]

DMG in basic solution is your friend in this instance. Ph needs to remain highlly acidic during and after the DMG addition. Search 4Metals posts on basic dmg and proceed with precipitation of Pd in normal fashion. Nitrates will pose no difficulty as long as other PGMs/Ag/Au are absent. Other PGMs will produced contamination evident by odd color DMG precipitate (eg: Greens, oranges, and reds not yellow). Odd colors are easily cleaned from preciptate using nearly concentrated HCl washes or water in minor discoloration cases.

Steve

 

[lazersteve]

For purely Pd and nickle solutions I have found that Aluminium foil works a treat for high purity Pd. Of course for maximum purity I would refine the Pd a second time to eliminate trace drag down and other impurities associated with using Aluminium. Make sure the pH remains around 1-2 during and after Aluminium additions.

Steve

 

[Alondro]

For purely Pd and nickle solutions I have found that Aluminium foil works a treat for high purity Pd. Of course for maximum purity I would refine the Pd a second time to eliminate trace drag down and other impurities associated with using Aluminium. Make sure the pH remains around 1-2 during and after Aluminium additions.

Steve

This will be useful for me when refining Pd from MLCCs. There will be a significant fraction of dissolved nickel from MLCCs with mixed electrodes.

I would assume you must eliminate as much free nitrate as possible and add HCl, or else the Al will form highly insoluble aluminum nitrate.

 

[lazersteve]

I use AP to dissolve the Pd with mlccs so nitrates are a non-issue.

Steve

 

[fabriciomnarvaez]

For purely Pd and nickle solutions I have found that Aluminium foil works a treat for high purity Pd. Of course for maximum purity I would refine the Pd a second time to eliminate trace drag down and other impurities associated with using Aluminium. Make sure the pH remains around 1-2 during and after Aluminium additions.

Steve

Correct me if I'm wrong. I will put 4g of caustic soda in 100 ml of hot water and another 5.81g of DMG, I will precipitate the palladium, it will probably turn canary yellow, so I will wash the DMG-PD and put it back in nitric acid to dissolve the palladium again , and lastly cement it with aluminum so that it is already metallized? is it correct?

 

[Yggdrasil]

Correct me if I'm wrong. I will put 4g of caustic soda in 100 ml of hot water and another 5.81g of DMG, I will precipitate the palladium, it will probably turn canary yellow, so I will wash the DMG-PD and put it back in nitric acid to dissolve the palladium again , and lastly cement it with aluminum so that it is already metallized? is it correct?

No I think he describes an alternative way without DMG.
He dissolves his Pd in HCl/Peroxide and drops it with Al, but this is only an alternative if the Pd solution only contains Nickel.

 

[lazersteve]

Correct me if I'm wrong. I will put 4g of caustic soda in 100 ml of hot water and another 5.81g of DMG, I will precipitate the palladium, it will probably turn canary yellow, so I will wash the DMG-PD and put it back in nitric acid to dissolve the palladium again , and lastly cement it with aluminum so that it is already metallized? is it correct?

I think this topic, like many, has taken two paths.
Let me see if I can bring them back together in a complete answer:

Pd dissolved in nitric acid can be precipitated using basic DMG solution prepared by 4Metals description already referenced. The pH of the nitrate solution must remain acidic throughout the process. The collected yellow Pd-DMG compound is collected, washed with water several times and finally calcined.

The resulting impure gray sponge with peacock colored highlights is then covered with 2-3 times its volume of 32% HCl and 30% Hydrogen peroxide added in small (1/10 volume) increments while heating (30-40C max) and stirring. Be sure your reaction vessel has at least 1/2 its total volume in headspace as the reaction foams and emits chlorine gas.

Allow each peroxide addition to fully react before adding another. The endpoint of each small peroxide addition is evident when chlorine is no longer being produced by the reaction.

When the Pd Sponge is fully dissolved filter out any sediments rinsing with water until the rinse water is clear. Combine all rinses with the mother liquor.

At this stage there are numerous routes to finish, but I will Segway into the one discussed above.

The deep burgundy solution can now be treated with pure aluminum foil to recover the fluffy black/dark gray palladium moss. The solution should remain below pH 4 throughout the process and be constantly stirred. Hydrogen gas is produced so work in a well ventilated area. Add Aluminum foil until no additional moss forms with a fresh Al foil strip.

Allow the moss to settle completely and decant off liquid (typically pale apple green to clear). Rinse until clear with water, stir, settle, and decant away liquid from sponge.

Prepare a rinse solution of 5 ml of 31% HCl in 95ml of water (approximately 0.5 molar) and wash the black sponge to remove any trapped Aluminum compounds.

Perform a final clean water rinse 3 times with stirring and settling between each rinse.
Collect the relatively pure (98%+) Pd, compress, and melt.

Higher purity is possible depending on your attention to rinses and other factors not discussed. As mentioned previously this but one of many routes to Pd metal.

Steve

 

[Lino1406]

With the presence of nickel, I'd suspect DMG addition will result in red nickel-DMG complex

 

[Yggdrasil]

With the presence of nickel, I'd suspect DMG addition will result in red nickel-DMG complex

Don’t it have to be caustic for that?

 

[Lino1406]

Don’t it have to be caustic for that?

From experience, no

 

[Yggdrasil]

From experience, no

Ok.

 

[kurtak]

With the presence of nickel, I'd suspect DMG addition will result in red nickel-DMG complex

This is correct - at least to a point - if nickel is also in solution you will likely get "some" co-deposit of nickel which will result in orange/red precipitate instead of yellow

HCl washes should remove the nickel

In the pic the bowl to the left shows DMG/Pd precipitate from Pd/Ni solution - bowl to the right is DMG/Pd from Pd/Ag solution - bowl at bottom shows show's DMG/Pd after calcination

Kurt

 

[kurtak]

I went to try to cement the PD with CU, and the Nitric dissolved the CU and didn't cement the PD

If all the copper was dissolved & no Pd precipitated it is because you had WAY TO MUCH nitric in the first place

The Pd will not cement out until the solution is completely loaded with copper (the free nitic is used up by dissolving the copper)

Warning - when cementing Pd with copper you MUST have VERY aggressive agitation of the solution otherwise the Pd will make a "tight" bond to the surface of the copper causing the cementing process to slow down &/or even stop resulting in Pd stuck to the copper &/or copper contamination of the cemented Pd

Aggressive agitation can be provided to the solution with ether an air bubbler (if solid copper is being used) or with stirring (if copper powder is being used) the agitation needs to be aggressive

Read this thread ---------

https://goldrefiningforum.com/threads/fuzz-button-interconnects-need-some-advice.22203/#p232030
Kurt

 

[Yggdrasil]

I think this topic, like many, has taken two paths.
Let me see if I can bring them back together in a complete answer:

Pd dissolved in nitric acid can be precipitated using basic DMG solution prepared by 4Metals description already referenced. The pH of the nitrate solution must remain acidic throughout the process. The collected yellow Pd-DMG compound is collected, washed with water several times and finally calcined.

The resulting impure gray sponge with peacock colored highlights is then covered with 2-3 times its volume of 32% HCl and 30% Hydrogen peroxide added in small (1/10 volume) increments while heating (30-40C max) and stirring. Be sure your reaction vessel has at least 1/2 its total volume in headspace as the reaction foams and emits chlorine gas.

Allow each peroxide addition to fully react before adding another. The endpoint of each small peroxide addition is evident when chlorine is no longer being produced by the reaction.

When the Pd Sponge is fully dissolved filter out any sediments rinsing with water until the rinse water is clear. Combine all rinses with the mother liquor.

At this stage there are numerous routes to finish, but I will Segway into the one discussed above.

The deep burgundy solution can now be treated with pure aluminum foil to recover the fluffy black/dark gray palladium moss. The solution should remain below pH 4 throughout the process and be constantly stirred. Hydrogen gas is produced so work in a well ventilated area. Add Aluminum foil until no additional moss forms with a fresh Al foil strip.

Allow the moss to settle completely and decant off liquid (typically pale apple green to clear). Rinse until clear with water, stir, settle, and decant away liquid from sponge.

Prepare a rinse solution of 5 ml of 31% HCl in 95ml of water (approximately 0.5 molar) and wash the black sponge to remove any trapped Aluminum compounds.

Perform a final clean water rinse 3 times with stirring and settling between each rinse.
Collect the relatively pure (98%+) Pd, compress, and melt.

Higher purity is possible depending on your attention to rinses and other factors not discussed. As mentioned previously this but one of many routes to Pd metal.

Steve

If I’m not mistaken you can dissolve the DMG-Pd salt directly.
KjavanB used HCl and Zinc directly if my memory serves me right.
Are there any pros and cons with calcining the salt before redissolving?
Besides the need to not overheat it.

 

[kurtak]

If I’m not mistaken you can dissolve the DMG-Pd salt directly.

I believe Lou posted something about that once - I am not sure how its done though

KjavanB used HCl and Zinc directly if my memory serves me right.

Yes that is another way of reducing the DMG/Pd salt to Pd

I does not dissolve the DMG/Pd salt though - it simply "reduces" the salt to actual Pd by ion exchange much the same as reducing AgCl with iron (instead of lye/sugar)

Kurt

 

[Yggdrasil]

I believe Lou posted something about that once - I am not sure how its done though

Yes that is another way of reducing the DMG/Pd salt to Pd

I does not dissolve the DMG/Pd salt though - it simply "reduces" the salt to actual Pd by ion exchange much the same as reducing AgCl with iron (instead of lye/sugar)

Kurt

Yes I'm aware of that, but I dropped the full explanation for an easy explanation.
There was already discussions on Al strips, maybe they can be used as well, instead of Zinc powder?

 

[lazersteve]

Here are some of the many colors of PdDMG you can encounter as well as a few shots of Pd Sponge, 99.9 fine Pd flake, and calcined Pd.

99.9% Fine Pd Flakes/Powder

Calcined and Sponge Pd high purity

Calcined Pd

Red PdDMG from high nickle solution

Various colors of PDDMG

Green PdDMG (Au contamination)

Washing Green Out of PdDMG with water

PdDMG Washing/Rinsing with HCl

PdDMG after HCl wash

Clean PdDMG precipitate

Steve