# Results on PGM Recovery



## KCGreg (Nov 6, 2009)

I just finished processing a few honeycombs of unknown makes and models and wanted to get some perspective on the results. 
Once all of the metal (about 48 grams) was forced out of solution and collected I put it right back into acid, straight HCl. I let this set on heat for about 30 minutes and observed no reaction. I added in a measured amount of nitric and it went straight to work. I observed the brown fumes, lots of bubbling and everything one would expect to see when metal is being digested by aqua regia. I boiled this until the action was complete and at the end there was nothing left in the bottom of the glass beaker. I tested this with stannous chloride and saw a positive test for pt, let that set for 30 secs and observed no color change to green. This lead me to believe there was more pt than pd. Precipitation is where I know notice that things got mixed up. I had no idea of how much pt was present so I used about an ounce of ammonium chloride to precipitate. I dissolved this in as little water as was necessary and after the solution had been properly evaporated. When I added the precipitant I got an immediate reaction and the red powder that I expected to see. After that had settled for about 15 minutes I tested with stannous and got a light reaction for dissolved pt and I watched this test again for about half a minute and observed no other color change which would indicate pd. I filtered off the red powder and repeated the precipitation process. I used 1/2 ounce of AmCl, again dissolved using no more water than was necessary and completed the precipitation with that final addition. initially,I assumed I simply had parts which contained only pt and no other pgms, weird but given my limited experience in refining these, I didn't think it was impossible. I cleaned the powder, I reduced to metallic and melted it into a 7.4 gram button which I thought was mostly a recovered and once refined platinum button. Well, the results from the scan showed that it was in fact 75%pd, 15%pt, 7% rh and a little less than 1.3% of base metals. 
I have a few questions about the results here: 1) How did the aqua regia dissolved the rhodium? 2) Why or how were all 3 pgms precipitated by AmCl? 

Thanks in advance


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## Lino1406 (Nov 6, 2009)

1. Very small particles of (black as precipitated) Rh will dissolve
2. Both Pd and Rh have double salts, as Pt. But it could be simple
chlorides who precipitated, too (Eventually the solution was saturated)
3. If you still have positive test with stannous chloride, try to get more
Pd precipitated by oxidizing the solution with chlorate


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## KCGreg (Nov 7, 2009)

Ok, some follow up questions here because my goal is to separate and refine the pt and pd and clean the rh as best I can. Is there any reason why I couldn't concentrate the hcl/clorox and precipitate any pt and/or pd present from that. And, then use the zinc to recover the rh? I guess I'lm looking at this process like I do pc processors. When I hit the chips with AR I don't use zinc to force the metals out, I precipitate the gold and then get to cleaning it before a refining. Can I do the same thing here? dissolve it with the hcl/clorox, then selectively precipitate the values I want, then it's just a matter of cleaning the calcined metal before a final refining. I could then force the other metals from solution and start cleaning to catch any left behind pgm's including any Rh?


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## Lino1406 (Nov 7, 2009)

That palladium is in majority. To
precipitate it selectively -
1. NO2 destruction with little Urea,
and,
2.Some ammoniac to raise pH
3.DMG solution


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## lazersteve (Nov 7, 2009)

If you evaporate HCl-Cl you will get a sodium chloride precipitate.

You can try to precipitate the Pd by adding NH4Cl followed by Sodium chlorate, but the diluted solution will dissolve any Palladium Ammonium Chloride formed as it is water soluble.

I've never tried it personally. 


When you saw red powder from ammonium chloride addition you should have known it was not pure platinum ammonium chloride which is yellow or light orange. You should have redissolved the metal sponge in dilute nitric first to remove the Pd, then in hot AR to more selectively strip the Pt for Rh.

Just as in gold refining, PGMs may require several cycles of dissolving and precipitation to fully separate the PGMs. With AR it's extremely important to remove the nitrate or Pd will come down with platinum. The free nitrate generates chlorine from HCl which precipitates Pd with ammonium chloride.

As Lino suggested DMG is a much better test for Pd than stannous.

Steve


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## KCGreg (Nov 12, 2009)

I thought that powder looked awful dark for pt, I think it's time to rewatch the video and take some new notes. Thanks guys, for all of your input it is very helpful and very much appreciated!


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