Problems in platinum recovery

[100tific]

The reason I suggested the nitric treatment is that it would remove the silver which been over 4 times the weight of PGMs would have also removed nearly all if not all of the PGMs , you can then create silver chloride which you could filter out and then cement the PGMs with copper leaving you a mix of platinum and palladium as metallics , rinse the recovered metallics in water and soak in nitric which will then remove the palladium leaving you with nearly pure platinum.
The gold would be easy to refine and recover using AR ,the silver chloride again easy to convert, the platinum is already fairly pure so the only value not recovered is the palladium which been such a small amount I’d simply again cement out and save the recovered metallics until I had enough to make the refining worth the effort.
To my mind this would produce the best outcome for your source material but I’m open to criticism and or other thoughts.

thanks nickvc, but i'm trying not to use cementation because i don't have cu powder yet. But i think it could be a good way too. maybe so much steps. I think if we have all metals in AR, we can selectively precipitate it one by one.

There are other female members but only a very few that participate actively. Maybe you can start a trend by your participation.

i hope so Shark, Anything else to add about my questions on platinum recovery?
thanks

 

[Shark]

thanks nickvc, but i'm trying not to use cementation because i don't have cu powder yet. But i think it could be a good way too. maybe so much steps. I think if we have all metals in AR, we can selectively precipitate it one by one.

i hope so Shark, Anything else to add about my questions on platinum recovery?
thanks

I know very little about the pgm's and can offer no help. Actually, I was hoping to learn from this post myself.

 

[nickvc]

As I have admitted I’m no expert with PGMs but trying to precipitate pure metals from a mixed dirty solution is not possible in my opinion, please anyone correct me if I’m wrong here, so you would have to refine the recovered metals again anyway, even using the nitric route you may still have PGM contamination in your gold.
A point about cementing is it can be done with an air bubbler and copper sheet or bars.
I fear that refining mixed values containing PGMs is not a simple one or two step process whichever route you decide which is why many simply recover the gold and silver and then recover the PGMs via the stock pot at a point when it makes it worth while.
4metals may have a different view and I would listen to what he has to say on this as he knows far more about these processes than me.

 

[Yggdrasil]

If I'm not mistaken the established practice is to dissolve it and then drop the Gold first.
Most sources say Ferrous Sulfate for this.
Then go for the Pt.
The Silver will largely be untouched with a small amount as Silver Chloride.
Agressivly stirred solution with a Copper bar or sheet will work just fine.
If you had used Silver for inquarting much of the Pt would have followed the Silver during parting and it would be easy to drop the Silver as Chloride.
Leaving just Pt in solution.
Then dissolving the Gold and drop that and you can combine the two fractions of Pt solution and Cement it or use Formate reduction to drop it.

Just make sure you have the highest possible lab hygene when you have PGM in solution.

 

[kurtak]

Lastly, I would also like to clarify that yes, I am a woman. I don't know why this has caused such a stir

No one was trying to "cause a stir"

In the beginning Martijn was referring to you as "he" simply because Martijn did not realize you are a women

So Dave (FrugalRefiner) was for clarification simply pointing out that you are not a man but in fact a woman

Women also do science, we also think, and we also love precious metals and their chemistry. I have been dedicating myself to this sector for 5 years, and I am very happy because I never stop learning and they never stop surprising me.
I would also like to say that I have read and studied Hoke's book, also a woman, and many other books before reaching this point.

I agree - when I was doing a joint venture with a scrapyard to refine their precious metal scrap my co-worker (co-refiner) was a women & she was VERY good at refining

Concerning your (starting) alloy - personally - I would have "upped" the silver so that everything (including the Pt) except the gold could be dissolved in nitric - rather then upping the copper & trying to dissolve everything except the silver in AR (resulting in AgCl)

One of the (potential) problems with going with a chloride solution (AR) on a complex alloy like this is the (potential) to creation of chloride salts (solids) other then just AgCl (as you now see) - this is less likely to happen in a nitrate solution (unless something like tin is in the alloy)

Ether way (dissolving Au + PGMs in AR - or dissolving Ag + PGMs in nitric) makes dropping the PGMs as chemical salt difficult (with the exception of dropping Pd with DMG) simply because PGMs do not like to chemically precipitate as salts from dilute solutions --- PGM chlorides/chlorates are VERY water soluble - so the solutions need to be very concentrated (water free)

That is why cementing the PGMs is the recommendation after dropping the gold (from AR) or after dropping the silver (as AgCl) from nitric

Some of the BIG BOYS have gone to using resins that are designed to be "selective" for "recovery" of the PGMs rather them cementation

Chemical precipitation of PGMs as salts (chlorides/chlorates) is mostly reserved to when the primary/only metal(s) in solution are the PGMs

Kurt

 

[4metals]

The classic assay books tell you in order to get all of the PGM's away from the Gold you should inquart with 10 times the Platinum content to allow if all to follow the Silver. That also implies making the Gold 25% or less. But the texts do specify this will cause all of the Platinum to migrate over. But if your parting has less than 10 times the Platinum as Silver there will be Platinum on both sides of the equation, meaning some Platinum remaining with the Gold and some Platinum following the silver. From a practical refining method, chasing PGM's two different ways is not efficient.

The inquartation with Silver to allow all of the Platinum to follow the Silver is only a reasonable option if @100tific has a Silver cell operating to recover the Platinum after cementing the Silver and any PGM's with copper and running it in a cell.

The aqua regia option would be my choice after lowering the Silver content below 9-10% with copper. The gold should be dropped first and with that much copper added it will not come down clean. It will need a second aqua regia refine.

Wether or not the copper causes issues with dropping PGM's completely if the copper completely dissolved it should not as cementation works on metallic copper. If it were me, I would cement the PGM's on copper, and a clean copper slab would work for this as well. Then, once the original solution is barren of values, the insolubles should be filtered and digested in aqua regia and the Platinum recovered either by ammonium chloride or cementing with sparing additions of copper powder.

As far as the Jahn-Teller effect is concerned it is commonly seen in transition metal complexes so copper does apply. The exact effect the Jahn-Teller effect will have on this particular reaction is subject for debate, there are so many variables that present themselves in acid refining that determining that would be a difficult process. Seeing as you have an alloy and apparently a customer or boss that wants to see the refined metal to sell it, I think the Jahn-Teller effect is a wormhole that may absorb your efforts for a very long time. On the bright side, your research may re-define refining as we know it and your efforts may result in a Nobel prize. Considering Nobel prizes in chemistry are awarded overwhelmingly to men, I would be happy to see it!