Mixed Black PGM Powders

[kadriver]

Sena:

Here is a post that has some pictures of the beads from catalytic converters:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=6356&p=65243&hilit=+beads#p65243

kadriver

 

[kadriver]

On Sunday 15 July, I completed the rinses to get the NaOH out of my mixed PGM black powders.

I decanted and left about 100ml of water on top of the clean black PGM powders.

Then I took it all outside (no fume hood yet) and began the next step to dissolve the palladium.

I added 100 ml of concentrated nitric acid to the mixed PGM powders with the heat off.

 

[kadriver]

After about 5 minutes, the reaction began. I could see red fumes beginning to form inside the reaction vessel.

 

[kadriver]

I turned the heat on to low, then to medium and the reaction increased

 

[kadriver]

As an experiment, I held a test tube containing ice water in the fumes to see if any metals would condense.

I wanted to see if any metals were escaping with the fumes.

A stannous test produced a negative result, but the pH test confirmed that acid (probably nitric from the fumes) had formed.

 

[kadriver]

After about an hour, the mixture began to boil slightly and the reaction and fumes increased.

 

[kadriver]

Edit spelling

At about 1.5 hours the fumes began to lighten, so I increased the heat to medium high.

The fumes incresed after about 15 minutes then dropped off fairly rapidly.

At the 2 hour 15 minute mark, the mixture was boiling rapidly and the fumes had ceased.

 

[kadriver]

I turned the heat off and let it cool slightly, then added 100ml distilled water.

I put the saucer back on and took the mixture inside to settle overnight.

using a flashlight, I backlit the beaker to show that the solution had begun to settle after about 1 hour.

 

[kadriver]

placed it on the hotplate stirrer and dipped a cotton swap for stannous chloride test.

I will let it settle overnight, then decant, rinse and treat again with nitric acid.

 

[RaoOvious]

excellent visuals and nice series.. keep it going kad..

 

[kadriver]

Thank you for the kind words - here is more of the process:

I decanted the Pd liquid into a 2 liter beaker - about 100ml only until I could see black powder start to make its way to the spout - so I stopped pouring.

I added about 1000ml distilled water and allowed it to settle for about 4 or 5 hours and decanted into the same 2 liter beaker with the 100ml Pd solution.

I then added another dose of 1000ml distilled water and allowed it to settle. This is as far as I got today.

As you can see, the liquid in the remaining black powder is begining to get clear.

once it is clear, I will do another nitric acid treatment to remove more palladium (if there is any left in the remaining black powder).

I will do this over and over until the nitric acid stays clear.

When the nitric acid stays clear after heating, then it is probably safe to conclude that all the palladium has dissolved and all that is left in the beaker is Pt & Rh.

The solution took a long time to settle - but I am in no hurry.

kadriver

 

[kadriver]

In this photo:

Tall 1 liter beaker on the left is the result of the second nitric acid treatment using 50/50 nitric acid/DH2O.

The color is very slight which tells me that the first concentrated nitric acid treatment dissolved nearly all of the Pd from the mixed black powders.

After adding the black powders from the Pd washes back in, I will decant this acid and save it to do the initial nitric acid treatment on my next batch of mixed black PGM powders.

Once decanted, I will add another 50/50 nitric acid treatment and repeat until the acid remains clear - saving the acid for future Pd treatments.

These repeated treatments will leave behind the Pt and Rh, free of Pd.



The 2 liter beaker in the middle is the decanted liquid from the first nitric acid treatment, plus the first DH2O wash water.

The color of this liquid resembles strong coffee - it can't be seen, put I predict that there will probably be a fine layer of black powder settled on the bottom of this container.

I plan to decant this liquid as my main palladium solution and then try to evaporated some of it off with gentle heat to concentrate - not sure if this is the right way to go.

I will then add distilled water to rinse the black powder on the bottom of this container, settle, decant to stock pot and add resulting black powder back with the other Pt/Rh powders in the tall beaker on the left.

Once this main palladium solution is concentrated, I will add ammonium chloride (not sure how much to add) and then chlorine via sodium chlorate a crystal at a time just like Steve's DVD recommends to precipitate the palladium salts.



The 1 liter beaker on the right is the second DH2O wash water from the initial concentrated nitric acid treatment.

Notice the fine layer of black powder that has settled on the bottom of the container.

This layer is probably Pt and Rh that came over when I poured the wash water off.

I will decant this to the stock pot and add the fine layer of black powder back to the tall beaker on the left for further treatment.

 

[lazersteve]

Kevin,

Great work as usual.

A tip that may help:

Take a small test sample and add DMG to remove the Pd. After filtering out the yellow Pd2(DMG) test the left over solution with stannous again for the presence of Pt. If none is present proceed with anyone of the suggestions below.

Check out this chart:

Precipitant Chart

You should be able to have success precipitating the Pd directly as a metal with SO2 or zinc. You can recover the red colored Pd salt by adding ammonium chloride directly. The red salt will need to be purified via this method:

Purifying Pd

Check your left over solutions with DMG.

Steve

 

[kadriver]

Steve:

I'll do as you suggested. I'll do the test on a small sample of the main Pd solution.

Thanks for the guidance.

Kadriver

 

[kadriver]

I drew off about 2ml of the main palladium solution and added it to a test tube.

I added about 5 or 6 ml of distilled water to the palladium solution.

I then heated my DMG test solution to redissolve the crystals that had formed.

I added about 5 or 6 ml of the DMG test solution to the test tube and precipitated the palladium out.

Then I allowed it to settle for about an hour until some clear liquid appeared at the top of the test tube.

I drew off some of this clear liquid and put 3 drops into two of the cavities on the spot plate labeled "A" and "B".

I added 3 drops of stannous chloride test solution to cavity "B" on the right and no stannous to cavity "A" on the left.

I could detect a slight tint of color after a few minutes.

The photo of the spot plate test is 30 minutes after adding the stannous.

The color looks faint orange to me - maybe some platinum in solution with the palladium.

Edit for pictures

kadriver

 

[RaoOvious]

Steve:

Doesn,t it go against the chemical dynamics of the process that nitric only dissolves palladium.So why there is your recommendation to test for platinum in palladium solution.

Rest: kad once again refreshing visuals.....keep em coming.....

 

[lazersteve]

Steve:

Doesn,t it go against the chemical dynamics of the process that nitric only dissolves palladium.So why there is your recommendation to test for platinum in palladium solution.

Traces of chlorides in the cemented mixed powders can lead to trace amounts of AR being formed, which in turn can dissolve Pt along with Pd in nitric acid milieu. Sister metals such as PGMs tend to follow one another in various reactions, especially when they have very similar precipitants and solvents.

When refining (especially PGMs) one cannot assume the reagents or the solids one is working with are pure, unless these exclusion tests are done. It is extremely difficult to completely separate mixed PGMs in one pass.

Steve

 

[kadriver]

Today, I poured off the second nitric acid treatment from the remain black powders - Ill save this acid to do the first nitric treatment of the next batch of black powders.

I then poured off the rinse water to another container (this should to to stock pot) and rinsed the settled black powder from the bottom of it into the Pt and Rh powders.

More distilled water was added to do a rinse from the 2nd nitric treatment.

Once this settles, I'll pour off the rinse water and do another dilute nitric acid treatment and repeat until it comes out clear.

kadriver

 

[kadriver]

You should be able to have success precipitating the Pd directly as a metal with SO2 or zinc. You can recover the red colored Pd salt by adding ammonium chloride directly. The red salt will need to be purified via this method:

Purifying Pd

Check your left over solutions with DMG.

Steve

Steve,

I found the ammonia/HCl process for repuricication of palladium on pg 177 of Hoke's book and the reference you gave above with pictures should get me through that process.

I can see where using zinc to get the Pd metal would also bring down the Pt and contaminate my Pd.

Therefore, I would like to precipitate the red Pd salt with ammonium chloride and then purify with ammonia and hydrochloric acid as instructed above.

But I am a bit confused about adding ammonium chloride directly to the palladium/nitric solution to get the red powder.

I can not find this procedure in Hoke. Of course, there were no cats leached in HCl/Cl back then either.

She says that adding ammonium chloride to a palladium solution (prepared with AR) will produce no precipitation - C.M. Hoke pg 108 para 3

And then she goes on to say that sodium chlorate must be added a crystal at a time to precipitate the palladium.

I realize that the palladium solution that I am working with was NOT prepared using aqua regia - only nitric acid.

I will add the ammonium chloride directly to the palladium/nitric solution as you recommend. Just looking for some clarification.

On page 156, Hoke mentions that some, "considerations ... are not easily explained to the non-chemist" so I will take that and apply to this step.

Thank you for your help!

kadriver

 

[goldsilverpro]

kadriver,

I've wanted to ask this question for a long time. Before taking these photos, do you first clean everything? I've never seen anyone that is more neat and tidy than you. I'm certainly not complaining, just curious.