Mixed Black PGM Powders

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kadriver

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Oct 25, 2010
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Hello:

I have about 10 grams of mixed Pt & Pd black powder.

HCl/Cl leach of some automotive cats.

Precipitated with 3000 mesh zinc powder and zinc turnings.

Washed with tap water and dried over low heat.

I have lazersteve's DVD, "Fundamentals of Processing Platinum and Palladium" and have used it as a guide to this point.

The next step on the DVD is to seperate the powders with AR.

I know some of the info on the DVD has changed and was looking for input on the next step in the process.

Using AR will require evaporation to remove excess nitric acid. Is this the best way to proceed?
 

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Kadiver - I have not done alot with the Pt group yet - however as I understand it the evaporation part of the procces is two fold. First is to rid any free nitric in the AR & second is to rid the AR of water as PGM salts are very water soluable - Then you can selectivly drop your PGMs - Pd then Pt

At least that is how I understand it.

Kurt
 
Kev

This is how i treat mix PGM black (though, not happen too often):
- Warm dilute sulfuric leach to remove Zn/Al and other BM - 1 part H2SO4 to 9 parts water - with constanst heating + stirring for one hour.
Decant and wash twice with hot water.
- Leach the powder with warm 50/50 nitric to remove Pd (and Ag if present). 1 - 2 hours with with constanst heating + stirring.
Decant and wash 2-4 times with hot water. Remove Ag (if present) with salt, treat the remaining solution as per usual for Pd (evaporate, then NH4Cl + Cl2).
- At room temp', cover the remaining solids with HCl and add 3-6% H2O2 under constant stirring to remove Pt.
Repeat this leach one or twice more to remove all Pt. Treat for Pt as per usual (evaporate, then NH4Cl)
- Remaning metallic solids should be mostly Rh.
 
kurt said:
Kadiver - I have not done alot with the Pt group yet - however as I understand it the evaporation part of the procces is two fold. First is to rid any free nitric in the AR & second is to rid the AR of water as PGM salts are very water soluable - Then you can selectivly drop your PGMs - Pd then Pt

At least that is how I understand it.

Kurt

True Kurt.

One more reason for evaporation and addition of HCl is to ensure all Pt is oxidized to Pt (IV) or in other words, chloroplatinic acid.
Pt (II) does not precipitate with NH4Cl. As far as i know.
 
Sam - Thank you.

I bought a hotplate stirrer at the urging of another forum member (glad I have it).

I will use the stirrer and try this one step at a time beginning with the sulfuric acid leach.

I appreciate the help.

kadriver
 
kurt:

Did not mean to skip over you like that. Thanks for the input. I need all the help I can get.

Sam has suggested using Nitric acid for the Pd, which will require evaporation.

Using HCl/H2O2 for the Pt will eliminate the use of nitrates when dissolving the Pt.

Today I added nitric acid and H2O to a little of the black powder in a spot plate.

The Pd came out nicely (tested with DMG to verify) and left the Pt alone

kadriver
 
Hello forum:

I decided to use the process outlined by lou with this small amount of mixed powders recovered from automotive catalytic converters.

Here is the link to that procedure: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=8742&p=82338#p82338

The first step in the process is to wash the black powder in sodium hydroxide (I am using Rooto drain cleaner from Ace Hardware) to remove any excess zinc powder.

Before starting, I made a solution of 10 grams of sodium hydroxide and 50 ml tap water for an experiment.

I put the NaOH solution in a beaker and onto the stir plate.

Then I added 1/2 gram of zinc powder to see how much of the zinc would dissolve in the NaOH solution.

Here are some photos of the experiment - it appears that some of the zinc powder was removed.

kadriver
 

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After this experiment, I put the mixed black powders into a 600ml beaker.
 

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Then I made a solution of 20% by volume NaOH by adding 40 grams of the Rooto drain cleaner (sodium hydroxide) to 200ml of distilled water.

I added this solution to the beaker containing the mixed PGM powders.
 

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I placed the beaker on the stir plate with no heat and stirred continuously for one hour.
 

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After an hour had passed, I poured the entire mixture into a tall 1000ml beaker and added tap water to the top of the beaker to begin rinsing.
 

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I let it settle for about 4 hours then decanted and added another 1000ml of tap water.

Tomorrow I will decant again and add another dose of tap water and let it settle again.

I plan to continue washing, settling, and decanting until I get a neutral pH test with pH test strips.

This is as far as I got today. I am going as slow as I can.

Any critical input from the forum would be greatly appreciated.

kadriver
 

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Concentrated, hot KOH or lye is used to remove both the zinc, the silica, and also alumina.


The PGMs are unaffected. You could probably just digest them all in room temp aqua regia, deNoxx and ppt the palladium with DMG. The residue will be the great bulk of the Rh. Unfortunately, the Pd will be heavily contaminated with Pt.
 
or you can use diluted HCl to get rid of any free zinc, then operate as usual as per ur preferred method,through AR or through Nitric and sulfuric washes to get rid of palladium and rhodium respectively and you would be left with almost pure platinum.

Diluted HCL wound not affect any of the pgm's in your black powder.

Lye creates problems in rinsing and washing the powder and further its too lazy to accomplish the task.
 
Thanks for the input. I have already begun the process outlined above so I am going to stick to it.

Today I rinsed again and after the fourth rinse got a neutral pH with test strips (see photo - sorry a little out of focus).

Once this settles, I am going to rinse one more time before I go to the next step.
 

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I wanted to be thourough so I repeated the experiment with 20% NaOH (lye) solution and zinc powder.

This time I used only 0.1 grams of zinc powder.

I measured out two identical piles of the zinc powder, each weighing 0.1 grams.

I put the first pile in the 20% NaOH solution (20 grams lye in 100ml distilled water) and stirred for about 30 minutes.

After 30 minutes I tilted the beaker to get the zinc powder to one side on the bottom of the beaker labeled "A" in the photo.

For comparison, I then added the second pile of zinc powder, labeled "B" and immediately took the photo.

I added the line to seperate the two piles.

Everything below the line is what is left of the 0.1 gram pile of zinc powder after being stirred for 30 minutes in 20% NaOH solution.

Everything above the line is the second pile that was added after the first pile was stirred. This second pile was added immediately before the photo was snapped.

You can clearly see that the first pile of zinc powder was partially consumed by the 20% NaOH solution as compared to the second pile of zinc powder added after the stirring.

I know this experiment was probably unnecessary and has already been done, but I wanted to satisfy my own curiousity.

kadriver
 

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I would like to stick to the process as outlined and remove the Pd with 50/50 nitric next.

I can save the resulting Pd/nitric solution until I get a sizeable amount and then process it all at once later to get the palladium out.

What I would really like to have for now is a nice button of platinum.

I have about a dozen more cats to leach (not counting four more with metal substrate) plus I bought a bunch of beads.

The beads can be leached several times with nice yields from each individual leach.

Thanks - kadriver
 
Thanks Steve.

For some reason I left the NaOH wash at room temperature. Would it be more effective if heated to medium or lower heat?

Also, I mentioned using 50/50 nitric acid/DH2O. But I noticed that lou had said to use concentrated nitric to remove the Pd, so that is what I will do.

Here is some fresh leach liquid from some cat beads. These beads keep on leaching pregnant solution. This is 2nd leach from about 4lbs of beads using HCl/Cl.

Beaker on the left has been has been course filtered and fine filtered with a Whatman #5 fine filter paper with vac assist.

Beaker on the right is being course filtered. There was much carbon from combustion on the beads - next time I will pre-wash with water before leaching

Tomorrow I will remove the Pd with nitric and post more photos.

kadriver
 

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Good picture brother, i just need to know how the " cat beads" are and curious to know how it looks like .i never opened catalytics, can you please post some
picture brother.

Thanks
Sena
 
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