# Pd – DMG – Co-deposit contamination



## kurt (Jul 21, 2012)

Ok what’s up here – DMG is supposed to be “very” selective in presiping “only” Pd (from an acidic solution) & nickel (acid neutralized with ammonia)

The filter on the left is clearly the Pd canary yellow to be expected (this one came from a test dissolve of some points that turned out to be pure Pd points)

The one on the right which is from a dirty solution that test positive for Pd with stannous – it’s a dirty solution because again it came from a batch of points & some of the Pd went into solution when using nitric to rid most of the bus bar base metal. (for more info on this solution see my thread titled Need confirmation on PGM test here in the PGM forum)

I never really got answer to my stannous test in that thread (which is a 2 colour test result) & now here on a DMG drop test I am getting a Co-deposit contamination.

I have not worked with a lot of the PGMs & so am still on a big learning curve here.

Both filters came from nitric solutions. The one on the right is the one I need to figure out so I can figure out how to treat the greater bulk of the solution.

Kurt


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## lazersteve (Jul 21, 2012)

You can digest the darker powder with 10% ammonium hydroxide, filter, and precipitate with HCl to purify.

The left over solids can then be treated via incineration and be refined a second time.

Here's a thread on the repurification of Pd:

Purifying Dirty Pd

The process will work on Pd from DMG, but it will be difficult to get all of the dirty compound dissolved in the ammonium hydroxide.

Steve


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## kadriver (Sep 18, 2012)

kurt:

I encountered the same impure precipitation from the palladium DMG.

Did you redissolve the impure palladium DMG precip (the one on the right in your photo) in ammonium hydroxide to repurify?

The bottom photo that I posted below shows both precipitations from my solutions drying in their filters.

The one on the left is some clean Pd salt precipitated with HCl from an ammonia extraction of the sparingly soluable brown colored (NH)4PdCl4(Ammonium terachloropalladate).

The one on the right is from left over solutions scavenged with DMG.

My photo looks very similar to your photo in this post.

I was just wondering what results you got, if any. 

Thank you - kadriver


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## Lou (Sep 18, 2012)

The high surface area of the DMG precipitate (it's very fluffy) means lots of drag-down.


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## kadriver (Sep 18, 2012)

To purify the DMG palladium salt pictured on the right, I am thinking that all I have to do is redissolve in 10% ammonium hydroxide, filter out contaminants, and acidify with HCl.

The resulting palladium salt should look clean and identical to the salt on the left of the photo.

I would have thought that the contaminants would have been removed by the first dissolution in the ammonia.

kadriver


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## Lou (Sep 19, 2012)

Not necessarily so.

It is entirely possible for contaminating elements to form ammine complexes that are quite stable and can ride down with the Pd(NH3)2Cl2.


Lou


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## kadriver (Sep 19, 2012)

I kind of thought that would be the case - not an easy seperation here.

I am glad I did not mix the brick red and the Pd DMG in the same container. Looks like the Pd DMG would have contaminated the whole batch.

kadriver


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## lazersteve (Sep 21, 2012)

It is irrelevant as to what is dragged down because you are going to redissolve the DMG compound and re-precipitate as the ammonium chloride compound. The drag down will be mostly eliminated in the next step. The drag down would only present a problem if the DMG were to be incinerated and melted immediately thereafter. Even then it would only be there in a small proportion if you have been careful in your work.

By not mixing the two salts you have extended your time involved and created more volumes of solutions with trace Pd in them. Ultimately any impurity that would follow the DMG should be further removed in the ammonium hydroxide stage.

Even if you keep all of your Pd DMG salts separate through the entire process, ultimately when you sell the material any trace elements that made it through the purification steps will end up in the Pd DMG only button anyway and will affect the overall batch purity (DMG Pd and non-DMG Pd salts) and payout in the end. In a nutshell your buyer is going to dock you for any trace elements when he/she analyzes the Pd and it all ends up in the same pot after all is said and done. Whatever traces that are destined to make it through your purification process are going to be there regardless of which 'stream' you keep them in. These impurities will be in the same percentage proportion of the total batch, statistically speaking, regardless of whether or not the two Pd salts are combined before re-purification or not.

This is a good example of the difference between practical chemistry and analytic/theoretical chemistry. In my opinion it comes down to how valuable your lab time is and what can you achieve in the same amount of time verses the payout in the end.

Steve


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## kurt (Sep 23, 2012)

kadriver - sorry for the delayed responce - i have been very busy & just noticed your post to this thread.

I haven't done anything with my dirty DMG-Pd salts yet because I don't have enough worth messing with at this time & I am going to be adding more to it in the future (coming from the same source) so will deal with it then.

Anyway just wanted to say thanks for posting the pics kadriver

Also thanks Steve & Lou for posting your answers to this as they will come in very handy when I get ready to clean up my dirty DMG-Pd

Kurt


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## Lou (Sep 23, 2012)

We usually just put the DMG back into the aqua regia with more Pd. Dissolves pretty quick. 

Doesn't dissolve that well in ammonia!


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