# Unlocking palladium from AgCl - or better separating technique ?



## orvi (Aug 9, 2022)

I recently acquired around 80g of silver-palladium alloy contacts with approximate 20% Pd content. I intend to refine them by dissolving in nitric acid and then dropping the silver with salt water. Palladium would be then reduced with formate.
But, when dropping AgCl from palladium containing solutions - it always lock some Pd int othe AgCl. It is then "dirty", brownish coloured, and it cannot be easily washed out with water or dilute HCl out from the precipitate. 
What could help to wash it out ? Should I just let it stirr for few days with dilute (like 3-5%) HCl, or is it because I added it too quickly without vigorous stirring (palladium chloride hypothetically formed, which is of low solubility in water) ?


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## 4metals (Aug 9, 2022)

For a small quantity like you have can you drop the Palladium from the Silver Nitrate solution with Dimethylglyoxime? Then drop the Silver last.


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## orvi (Aug 9, 2022)

4metals said:


> For a small quantity like you have can you drop the Palladium from the Silver Nitrate solution with Dimethylglyoxime? Then drop the Silver last.


I have some quantity of DMG available, but I do not have proper setup to incinerate the complex. And it always end up in Pd loss after incineration :/ at least for me. I do not know what is the "usual" loss, when incinerating DMG complex in the air as it should be done, but for me it was always in range of %´s. Not actually lost, I recovered it from the refractory wool, with which the crucible was covered... But anyways, another trouble.

But if the precipitation of AgCl would behave like it always did, I wouldn´t have much more choices. I wondered about re-processing the AgCl... But my tired brain does not came to any solution, other than re-making metallic Ag and then redissolving and redropping it, leaving leftover Pd in solution. Redissolving AgCl in ammonia does not get me much further, as palladium also redissolve to amino-complex. And DMG does not work well in basic enviroment.


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## snoman701 (Aug 9, 2022)

orvi said:


> But if the precipitation of AgCl would behave like it always did, I wouldn´t have much more choices. I wondered about re-processing the AgCl... But my tired brain does not came to any solution, other than re-making metallic Ag and then redissolving and redropping it, leaving leftover Pd in solution.


It would, but you will effectively reduce the concentration of Pd in the remaining supernatant by a substantial amount. Once to that point (a second crystalization of AgCl, conversion back to Ag) the remaining Pd is likely within the realm of what a silver cell will effectively separate.


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## Yggdrasil (Aug 9, 2022)

orvi said:


> I recently acquired around 80g of silver-palladium alloy contacts with approximate 20% Pd content. I intend to refine them by dissolving in nitric acid and then dropping the silver with salt water. Palladium would be then reduced with formate.
> But, when dropping AgCl from palladium containing solutions - it always lock some Pd int othe AgCl. It is then "dirty", brownish coloured, and it cannot be easily washed out with water or dilute HCl out from the precipitate.
> What could help to wash it out ? Should I just let it stirr for few days with dilute (like 3-5%) HCl, or is it because I added it too quickly without vigorous stirring (palladium chloride hypothetically formed, which is of low solubility in water) ?


Have you tried Nitric?
Wouldn’t that redissolve the Pd?
Or do you think the Pd is locked in?

A friend had a similar problem with Gold. When he dropped the AgCl it became dirty brown.

He put it in AR and it became white as snow again. He have no analytic equipment so it is based on plain observation and estimation.


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## orvi (Aug 10, 2022)

snoman701 said:


> It would, but you will effectively reduce the concentration of Pd in the remaining supernatant by a substantial amount. Once to that point (a second crystalization of AgCl, conversion back to Ag) the remaining Pd is likely within the realm of what a silver cell will effectively separate.


Yeah. It isn´t big ammount of material, so if something goes bad, it wouldn´t be an issue to just reduce all dirty AgCl back to metallic silver and start all over. But I wanted to know if there is some hack or anything for washing it.

OwlTech has one video, where he was parting silver and palladium by hydrolytic precipitation. Also nice route - to PdAg nitrate, he was adding potassium hydroxide until the solution loose colour - Pd precipitated as hydrated oxide alongside with some silver. Then he filtered the mainly Pd hydroxides, and washed the cake with concentrated HCL - this liberate Pd to the chloride solution and remains of Ag convert to AgCl. Solution could be then diluted to squeeze out some extra AgCl, and filtered -> reduced.


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