Non-Chemical Dental sweep for recovery of the values.

[nickvc]

I have been presented a small bag of what I was told was a dental sweep. I incinerated the bag it came in and all the powder inside slowly raising the temperature to achieve a dull red glow all over.
This I then sieved to remove any over size pieces or metal objects, I took a small sample of what now resembles jewellers bench sweeps and had it scanned on an xrf gun. The sweep seems to have mainly gold and palladium as far as values go but I think also a fair amount of non metallics.
I'm not really set up to properly refine Pd so I want to recover the values but get rid of the inn metallics. My thoughts were to dissolve all the metallics in AR, filter and cement the values back out with copper.
My question is is this the best method or is there another way staring me in the face I can't see?

 

[Barren Realms 007]

You can dissolve everything like you are talking about, drop your gold out of solution then evaporate your solution down and drop your Pd with zinc or copper.

 

[Harold_V]

You can dissolve everything like you are talking about, drop your gold out of solution then evaporate your solution down and drop your Pd with zinc or copper.

I agree with this in concept, but with some slight changes.

I'd give the lot a good, prolonged wash (low boil) in nitric, which will remove silver and other base metals, and, perhaps, some palladium. The silver and palladium traces would then be recovered with copper.

I would then dissolve the lot in AR. After proper evaporation, I'd recover the gold using the precipitant of choice. I would wash the gold well, adding the wash water and acid to the remaining solution, which should contain palladium, and likely even platinum. Those I would then recover with copper. At some point, you'd have to separate the gold from the balance, and there's no better opportunity than when you have it in solution.

I see no need to evaporate to recover the platinum and/or palladium. Concentration isn't a requirement for cementation, and can work to disadvantage. The only exception I can think of would be to reduce the level of free HCl, which may or may not be troublesome. If it is not, I certainly wouldn't waste any time evaporating. I also would not use zinc, which is not selective and will also cement base metals. It's highly unlikely that all will have been removed with the initial nitric wash, although they should be drastically reduced.

Harold

 

[nickvc]

I have had the powder re scanned and it seems as if there's 20-30% of Pd around 5-10% Au and the majority of the the balance is cobalt. Bear in mind I'm not interested in refining this just removing the values from the rubbish and base metals as I get no more for fine metals than mixed alloys, to this end does anyone feel there's a better method than the one I outlined?

 

[nickvc]

Another thought is to spread the powder thinly over some newspaper and run a magnet over it, as cobalt is magnetic but all the other metallic elelments aren't I'm wondering if this will pull out the cobalt and just leave the palladium,platinum and gold making the recovery much easier and possibly even meltable... 8)

 

[4metals]

Cobalt is soluble in nitric acid. Quick and easy try a nitric dissolve leaving gold behind, with any Pt, filter out the Au solids and recover the Pd by cementing the acid.