# Mixed Black PGM Powders



## kadriver

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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## kurt

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


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## samuel-a

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.


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## samuel-a

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.


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## kadriver

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


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## 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


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## 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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## kadriver

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


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## kadriver

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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## kadriver

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


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## kadriver

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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## kadriver

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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## Lou

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.


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## RaoOvious

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.


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## kadriver

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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## kadriver

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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## kadriver

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


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## lazersteve

Great series of posts Kevin... good job.

Steve


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## 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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## sena

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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## 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


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## 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.


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## kadriver

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


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## kadriver

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


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## 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.


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## kadriver

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


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## 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.


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## 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.


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## 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.


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## RaoOvious

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


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## 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


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## 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.


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## 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


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## 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


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## 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


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## 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.....


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## lazersteve

RaoOvious said:


> 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


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## 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


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## kadriver

lazersteve said:


> 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


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## 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.


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## lazersteve

The data I compiled in the chart I posted above is from several very early chemical text that clearly states plain ammonium chloride will precipitate Pd from nitric solutions.

In Hoke she is assuming we have mixed PGM solutions, in these cases the solution is denoxxed to allow partial separation of the Pt and Pd. Since your solution is primarily Pd in nitric solution you shiould be fine with NH4Cl only. Make sure the Pd solution is very concentrated (blood red, burgundy wine color) before adding the saturated solution of ammonium chloride (37.2 g/100mL @20C). Remember that adding ammonium chloride to water will produce a cold solution (endothermic), so less than the above stated amount of NH4Cl will dissolve in the given volume of water. I typically make up a large bucket of saturated NH4Cl solution to keep in the lab with excess NH4Cl crystals in the bottom to assure saturation. Allow this mix to sit for sometime before using as the salt does not instantly dissolve, before use it should still have solid crystals in the bottom. Make sure you don't add any solids to the Pd solution when precipitating. It's fine to perform the ammonium chloride addition at room temperature or below. 

You should try a small sample of the cold concentrated solutions (Pd nitrate and ammonium chloride) to be certain you will get precipitates when they are mixed. If your sample does not precipitate a brick red (or lighter towards yellow) salt as soons as you add the solutions together, one or both of the solutions is not concentrated enough. 

If you Pd salt precipitates as a bright yellow color, it is very pure and does not need to be repurified. If it is darker colored towards brick red it needs purification.

Pure Pd Colored Powder:







Dirty Pd Colored Powder





If the color is darker than the first photo, repurify it.

Keep me posted on your progress.


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## kadriver

GSP:

I try to keep things tidy to aid my work - but yes, I do a little prep work before I shoot the pictures such as wiping off the surfaces and laying down paper towels.

It makes for a better shot and excludes clutter. Thank you for the compliment.

Steve:

I'll do a small test batch using the amounts and procedures outlined above. If I need to concentrate the main Pd solution, then I will just heat it on low and evaporate some of the excess liquid before precipitating.

Thank you for guiding me through the process.

kadriver


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## kadriver

Hello:

I performed an experiment on a small test batch of my main palladium nitric solution to see if I could get a precipitate.

First, I filtered the solution with fine filter paper.


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## kadriver

Then did a stannous chloride test...


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## kadriver

I made a saturated ammonium chloride solution using 50ml distilled water and a little over 20 grams of ammonium chloride.

Upon adding the ammonium chloride, the beaker chilled and the powder was not dissolving very well so I added a little heat.

Once the heat was added (two five second periods in the microwave) nearly all the powder went into solution and the resulting solution was clear.

Edit to add a picture


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## kadriver

I poured 50ml of the palladium solution into a 250ml beaker.

Then, using a disposable pipette, I drew off the ammonium chloride solution about 3ml at a time an began to add it to the palladium solution.

At first I could see a light colored precipitate start to form. I added about 25ml of the saturated ammonium chloride solution to the palladium solution.

The solution turned cloudy, but I did not see any red precipitate.


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## kadriver

I concluded that the palladium solution was probably not concentrated enough.

So I added a small teflon stir bar and placed the beaker on the hotplater stirrer on low heat to evaporate some of the liquid.

It took a while (about 2 hours), but I got what appears to be brick red precipitate.

I guess the next step is to repeat this experiment but first evaporate the palladium solution down with low heat before adding the saturated ammonium chloride solution.

Thanks for looking - any comments or critique always welcomed.

kadriver


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## lazersteve

Great work.

You can evaporate the Pd solution to 1/2 or less of it's original volume then repeat the test, you may need to heat the solution to get the brick red precipitate to form. Typically a saturated solution of Pd is so dark red you can not see through it.

Use DMG to scavenge the last of the Pd from the dilute pale yellow solution. This yellow Pd(DMG)2 can be added to the brick red precipitate and the mixed colored powders treated as described in the Purifying Dirty Pd post cited above.

The final resulting bright yellow Pd salt is then calcined, treated with zinc-acid, or base-hydrazine to get a very pure Pd sponge. 

You are showing other members a perfect example of the processes related to recovery and purification of Pd, thank you for your dedication to the forum.

Steve


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## RaoOvious

As always great to see those visuals and inputs of Steve along together...Keep up the good work...


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## kadriver

Hello:

The precipitate looks a bit over-cooked with a slight crust and very little liquid.

I began the next steps by making a 15% ammonium chloride solution by adding 30 grams of ammonium chloride to 200ml distilled water.

I preheated the water in the microwave for about 40 seconds - it was not boiling, but very warm to the touch.

I added the ammonium chloride to the heated water and it dissolved quickly and completely.

I then used the 15% ammonium chloride water to rinse the sides of the beaker.


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## kadriver

Steve, thank you for your comments - I am enjoying the experience.

kadriver


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## kadriver

I then set up a filter and filtered the brick red powder.

I used the 15% ammonium chloride solution to wash the sides of the filter paper and to rinse the powder out of the beaker into the filter.

I also added about 9ml 15% ammonium chloride water to rinse the powder in the bottom of the filter and waited for the filter to run dry.


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## kadriver

After allowing the powder to run dry in the funnel, I removed the filter paper.

I opened the filter and spread it out on some paper towels to dry.

I will allow this powder to dry completely and add it to the rest of the powder later on.

kadriver


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## kadriver

I'll test the filtered solution with DMG, recover any Pd/DMG precipitate, and add to the brick red powder before purifying.


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## kadriver

Rather than repeating the experiment with another 50ml, I elected to go ahead and slowly evaporate the main Pd solution since I got the desired result from the first experiment.

The Pd main solution must be highly concentrated before adding the ammonium chloride to precipitate out the Pd.

I began by transfering the main Pd solution to an open container to facilitate the evaporation process.

I then moved everything outside since I do not yet have a suitable fume hood.

I placed the container on low heat to concentrate it before adding the ammonium chloride.

kadriver


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## RaoOvious

way to go kad.....keep em coming


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## lazersteve

Kevin,

No need to let the brick red powder dry fully. Slightly wet PGM powders are safer as they do not get airborne when handled and cause allergic reactions if they get in your eyes, lungs, or on your skin.

Rinse brick red salts and Pd(DMG)2 with water directly into beaker and dissolve in 10% NH4OH with lots of stirring.

Slimey or colored solids left in the ammonia solution is fairly normal. Filter these out until the solution is 100% transparent and free of particulate. Add >30% concentration muriatic acid to the ammonia solution with stirring until pH shifts acidic. Don't breath the thick white fumes (ammonium chloride vapors) when mixing.

Steve


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## Lou

Palladium isn't nearly as dangerous as platinum, but still, exercise good chemical hygiene.


You want to precipitate the palladium with ammonium chloride and sodium chlorate in the cold and make sure there isn't an excess of free chlorine (you can risk NCl3 formation). Also, you want to be over 50 g/L Pd but not overly high (200 g /L) because of drag down with other elements. Your solution should be largely Pt free. Pt and Pd are very difficult to separate if you don't have an ORP meter and are doing it conventionally and not using DMG (even then, precipitate the Pt first, rinse well, and then go after the Pd). DMG is for scavenging Pd, not for practical refining because it is so porous/fluffy/high in surface area, it will retain a lot of other PGMs and base metals.


I've attached two photos of what yours should look like. This precipitation was done at ~70 g/L and as you can see from the raffinate, it's possible to get very, very nice results (how many mg Pd+2 do you really think is left in solution per liter?). This is how yours should look kadriver--you've done everything right to this point. This material was pure enough it needed not the ammonia treatment and was calcined in the hood and then post-reduced with H2 in the tube furnace. 


A note about the ammonia treatment:

when at first you do it, you may see a pink then fleshy precipitate appear--keep adding ammonia and let it digest. You really don't want the pH above 10, so it's easy to rush over much. Most of the gunk will precipitate at 2. I do two filtrations on it: 1 at pH 10, 1 at pH 8. Then take to pH 2-2.5 and filter again. The hydroxide cakes will hold up significant Pd; consider this a polishing step after your Pd is already 99%. 

Just because it is nice and yellow doesn't mean it is pure, as the other PGMs can readily contaminate it and leave no visible trace. It will not remove Pt well unless the solution volume is high and the Pt content is less than 0.2%, and then Pd begins reporting appreciably. I am *NOT* (let me be emphatic here) a believer in using zinc EVER to reduce fine palladium produced from this procedure and disagree with Steve wholly on that. I am fine with it for platinum, because the zinc distills off at 1800C (probably into the lungs). If you want to reduce it, caustic soda and formic acid, 65-80*C. It is the best way to reduce palladium from the diammine. It gives a nice, easily filterered open pore precipitate, much like proper hydrazine application with ammonium hexachloroplatinate.


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## lazersteve

Lou,

There is no need for sodium chlorate in his precipitation reaction because he is precipitating from a nitric solution.

Steve


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## Lou

Oh yes, I see that now. Didn't read it all the way.  

Advice still stands.

From a nitrate solution it is possible, and preferred although that makes an inferior precipitate. It is preferred because it's safer and in his case, easier than syrupizing into a chloride and less manipulation. *It is not advisable to add ethanol/DMG/DMSO (any organic) to a concentrated nitric acid solution, especially when hot.* Therefore, ammonium chloride is a good avenue for this particular instance.


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## samuel-a

Lou said:


> If you want to reduce it, caustic soda and formic acid, 65-80*C. It is the best way to reduce palladium from the diammine. It gives a nice, easily filterered open pore precipitate, much like proper hydrazine application with ammonium hexachloroplatinate.



Few months back, i had refined about an ounce of Pd metal, eventually it ended up as palladosamine chloride.

I eventually end up reducing it by putting it in a concentrated NH4Cl solution and boiling it for about 3 hours under reflux. Hard boil, as high the the hot plate could get.

Result was very nice grainy and heavy black, that settles almost like gold powder does.
I have noticed that, around 120-130C decop' starts.

Left over Pd in solution was scavenged by dmg. When i get the chance to do this again, i'll take some pictures.


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## RaoOvious

Steve,

If one decides to follow another route "precipitating (NH4)2[Pd Cl4] a green colored precipitate by adding NH4OH to a chloride solution(HCl:H2O2) of Palladium,can & should it still be further purified by Ammonia and HCl treatment? 

And whats your opinion of this route except obviously there being an extra physical hazard of an added step(Palladium reduction with zinc as black after its parting from mixed pgm blacks through nitric washes).

Insight would be appreciated.


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## kadriver

lazersteve said:


> Kevin,
> 
> No need to let the brick red powder dry fully. Slightly wet PGM powders are safer as they do not get airborne when handled and cause allergic reactions if they get in your eyes, lungs, or on your skin.
> 
> Rinse brick red salts and Pd2(DMG) with water directly into beaker and dissolve in 10% NH4OH with lots of stirring.
> 
> Slimey or colored solids left in the ammonia solution is fairly normal. Filter these out until the solution is 100% transparent and free of particulate. Add >30% concentration muriatic acid to the ammonia solution with stirring until pH shifts acidic. Don't breath the thick white fumes (ammonium chloride vapors) when mixing.
> 
> Steve



Steve:

I'll make sure and keep that powder moist with a little of the 15% NH4Cl solution.

Can I use plain water on the powder?

I thought plain water would dissolve the brick red powder.




Lou said:


> (how many mg Pd+2 do you really think is left in solution per liter?).



Lou:

I am not sure of this number.

I have evaporated about 400ml from the 900ml of main palladium solution that I started with - it took 9 hours to evaporate that much liquid over low heat.

There is 500ml left (after evaporation) of the main palladium solution. I was going to take it down to about 300ml before precipitating.

There was probably no more than 2 grams total (estimated) of palladium that was recovered in the nitric treatment from the original 10 grams of black powder that I started with.

This estimate is really just an educated guess since my experince is nill and this is my first refining - it could be much higher or much lower.

I have some palladium standard test solution that I prepared that is 1 gram per liter - or 100mg per 100ml - or .1 gram per 100ml.

I will try to do some spot plate tests to determine the concentration of the palladium solution in the beaker as compared to this known standard test solution.




Lou said:


> Also, you want to be over 50 g/L Pd but not overly high (200 g /L) because of drag down with other elements.



I'll keep these numbers in mind for doing the precipitation - I am going to print these pages of instruction and keep them at my shop for further reference.




Lou said:


> From a nitrate solution it is possible, and preferred although that makes an inferior precipitate. It is preferred because it's safer and in his case, easier than syrupizing into a chloride and less manipulation. It is not advisable to add ethanol/DMG/DMSO (any organic) to a concentrated nitric acid solution, especially when hot. Therefore, ammonium chloride is a good avenue for this particular instance.



I have been using DMG solution that is dissolved in distilled water only - I usually have to heat it before use to dissolve the crystals that form when it is cold.

I will stick with the original plan to precipitate directly with saturated NH4CL (ammonium chloride).

Thanks to all for the input and help.

kadriver


----------



## lazersteve

Kevin,

Plain water is fine to get it out of the filter, since your next step is to dissolve in ammonium hydroxide. Just use as little water as required to get the Pd salt into the new reaction beaker.

Steve


----------



## lazersteve

RaoOvious said:


> Steve,
> 
> If one decides to follow another route "precipitating (NH4)2[Pd Cl4] a green colored precipitate by adding NH4OH to a chloride solution(HCl:H2O2) of Palladium,can & should it still be further purified by Ammonia and HCl treatment? ...



I don't recall seeing any green Pd salts when using AP, unless they are highly contaminated. Regardless of the color, if the colored powder tests positive for Pd via DMG, the purifying process will work. It's worth noting that if you are getting a Pd precipitation from AP with ammonium hydroxide, it is due to the in situ formation of NH4Cl in conjunction with the free chlorine in the AP. Are you sure your AP is free of Pt?

Typically when precipitating with NH4Cl in mixed PGM solutions, a *dark green *salt is indicative of a mixed Platinum salts called 'Magnus Salts'. In your question you specified a palladium solution, but if platinum is also present then I suspect you may be dealing with at least some Pt Magnus Salt, not solely Pd. According to freechemist there is also a Pd analog of the green Pt magnus salt, but it is *pink*.(1) You will likely encounter this during the purification of the dirty Pd salt.


Steve

Citation(1)
Palladium Magnus Salt Analog


----------



## kadriver

lazersteve said:


> Kevin,
> 
> Plain water is fine to get it out of the filter, since your next step is to dissolve in ammonium hydroxide. Just use as little water as required to get the Pd salt into the new reaction beaker.
> 
> Steve



Got it.

When the time comes to dissolve the brick red powder and the DMG precipitate in ammonium hydroxide, all I have is 29% solution that I bought from a chemical supplier.

I'll add it a drop at a time - I hope this will be the right stuff to use. If not, then I will get the right concentration.

kadriver


----------



## kadriver

I did the spot plate test to try and determine the concentration in grams per liter of my main palladium solution.

The test can be viewed here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=15177&p=153673#p153673

It looks like I have about 2 grams of palladium dissolved in 1 liter of liquid (if I did the test correctly).

To get to 50 grams per liter, I will need to evaporate this solution down to less than 75ml - somehow that does not sound right. 

kadriver


----------



## lazersteve

Go with the ammonium chloride test procedure I spell out above, as long as you get a precipitate when the two solutions are mixed you're golden. You can scavenge what remains in the Pd solution with DMG.

Cooling can assist the precipitation process, in effect decreasing the solubility of the resulting Pd colored salt when the two solutions are mixed. Check out my youtube video on precipitating Pt with potassium chloride.

Steve


----------



## Lou

Steve, the salt is called Vauquelin's Salt: Pd(NH3)4PdCl4 and is formed by the action of dilute ammonia on mixed valence Pd solutions.



Lou


----------



## RaoOvious

It reads like:

"Addition of ammonia to solutions of palladium(II) chloride first causes the formation of a pink precipitate of the binuclear complex Pd(NH3)4PdCl4, Vauquelin's salt, which is converted to soluble tetraammine palladium(II) chloride by further addition of ammonia.
Acidification of this solution with HCL yields the sparingly soluble light-yellow trans-diamminedichloropalladium(II) (NH3)2PdCl2."


----------



## RaoOvious

Main difference is that above cited process can be accomplished through PdCl2 (II) not H2PdCl4...


----------



## kadriver

I took the main palladium solution down to a little less than 100ml (approximately) by heating gently outside.


----------



## kadriver

I drew off about 10ml of the concentrated solution and added some saturated ammonium chloride solution.

I had to add a little heat to this small sample because at first there was no precipitate.

After adding a little heat, the precipitate formed.


----------



## kadriver

After a bit more evaporation, I added saturated ammonium chloride to the main palladium solution.

I added the NH4Cl until no more precipitate would form.


----------



## kadriver

I set up the filter and filtered the sample of 10ml through first.

The filtrate from the sample was a light golden color - same as the previous sample test I did.

Then I began to filter the main solution.

As soon as I bagan to pour the main solution into the filter, the filtrate became very dark in color instead of the light golden color I had seen before.


----------



## kadriver

It seemed to me that I did not add enough HN4Cl to the main Pd solution resulting in not all the brick red powder precipitating out.

I added some more HN4Cl to the dark colored filtrate and put it on the hot plate stirrer.

After about 1 hour, the brick red precipitate was forming.

This is as far as I got today.

Tomorrow I will add some more heat and stir until the solution turns light golden yellow and the brick red precipitate is settled out then filter.

Processing this material is much more difficult compared to gold and silver. 

kadriver


----------



## kadriver

Steve - I just read your post about letting it cool.

I have turned everything off for the day and will check it tomorrow.

It should be down to room temp by then - hope all the precipitate will come down when it cools.

kadriver


----------



## Lou

samuel-a said:


> Lou said:
> 
> 
> 
> If you want to reduce it, caustic soda and formic acid, 65-80*C. It is the best way to reduce palladium from the diammine. It gives a nice, easily filterered open pore precipitate, much like proper hydrazine application with ammonium hexachloroplatinate.
> 
> 
> 
> 
> Few months back, i had refined about an ounce of Pd metal, eventually it ended up as palladosamine chloride.
> 
> I eventually end up reducing it by putting it in a concentrated NH4Cl solution and boiling it for about 3 hours under reflux. Hard boil, as high the the hot plate could get.
> 
> Result was very nice grainy and heavy black, that settles almost like gold powder does.
> I have noticed that, around 120-130C decop' starts.
> 
> Left over Pd in solution was scavenged by dmg. When i get the chance to do this again, i'll take some pictures.
Click to expand...




I have never done that before, please follow up. I don't know how useful it would be if there is still Pd present, but if it is nice and heavy, that is what I like to hear. 

What worries me is that I don't know if all of the decomp products will be exclusively Pd metal, possibly PdCl2 can be formed...

In any case, I wouldn't use the method--if your Pd yellow is pure, formate or hydrazine are only used if you don't have a calcination oven. Calcining is still the best.


----------



## samuel-a

Lou said:


> please follow up.



will do.


----------



## lazersteve

Sam,

It seems to me if your red Pd ammonia chloride salt decomposed there had to be one heck of an ammonia chloride cloud coming out of the beaker. Must have been quite a mess, unless you cooled the exiting gas and allowed it to condense in a closed reactor.

Sounds like you basically calcined the salt from the solution.

Steve


----------



## samuel-a

Hi Steve


The Pd salt i'm referring to is not the red hexachloropalladate. But the yellow Palladosammine salt which has a subsentually lower decomp' point (and lower solubility).

It was all done in the solution, where the salt is in its solid state. So no cloud was produced. The water cooled condenser returns all vapoers back to the beaker.

All in all, the process was pretty neat.



lazersteve said:


> Sounds like you basically calcined the salt from the solution.



Yes, i think so too. The undissolved salt decomposed due to the solution temp'.

I hope i could reproduce this process (when i get more Pd) with the same results and share it here.


----------



## lazersteve

samuel-a said:


> The Pd salt i'm referring to is not the red hexachloropalladate. But the yellow Palladosammine salt which has a subsentually lower decomp' point (and lower solubility).


Sam,

I believe the two salts, the yellow and the red are the same salt:

*'palladosammine chloride' *(I believe you left off the chloride part by mistake)

according to Hoke pg 284:



Hokes Refining Precious Metal Wastes said:


> ...The residue contains the platinum, gold, and the rest of the palladium in a form particularly suitable for extraction with aqua regia,which is the next operation. From the solution of chlorides thus obtained, the gold is precipitated as brown gold by means of ferrous sulphate, and then the platinum as ammonium chloroplatinate by the addition of ammonium chloride, and lastly, *the palladium is precipitated as palladosammine chloride*. The only one of these operations which calls for special comment is the precipitation of palladosammine chloride. The palladium present as chloride is converted into soluble tetrammino-palladous chloride by the addition of excess ammonia solution according to the equation:
> 
> PdCl2+ 4NH3 = [Pd(NH3)4]Cl2
> 
> When excess of hydrochloric acid is added, the sparingly soluble yellow compound known as *palladosammine chloride* is precipitated according to the equation:
> 
> [Pd(NH3)4]Cl2 + 2HCl = [Pd(NH3)2Cl2] + 2NH4Cl



Notice she declares the name of the palladium salt as the same name before it is purified with ammonium hydroxide and after.

Perhaps I'm reading the passages wrong, but it seems to read that the Palladium is precipitated, then purified as the same salt. 

Regardless of whether they are the same salt or not, they are easy enough to convert back to Pd sponge via reduction or heating.

Steve


----------



## samuel-a

lazersteve said:


> I believe the two salts, the yellow and the red are the same salt:



As far as i can tell, the are not.

This is getting quite confusing though. From what i know:
Yellow powder, Palldosammine Chloride - Pd(NH3)2Cl2 is a coordination compound where Pd is at +2
Red powder, Ammonium Hexachloropalladate - (NH4)2PdCl6 is a simple ammonium salt where Pd is at +4 

Beside that, from my personal experience, they don't look the same and don't behave the same. So my only conclusion would be that they are not the same.


I'm sure Lou could help us set things stright with the proper terminology.


----------



## samuel-a

Upon firther reading, i can see the confusion now. I think you do missed something in the text Steve.

She calls for:
After addition of NH4Cl to precipitate Pt, she say to add ammonia (to produce soluble tetrammine complex, +4) and then re-acidify with HCl to precipitate a diammine yellow salt.
Just as you would re-refine you red powder. (Dissolve red powder with ammonia and precipitate with HCl)

The red powder precipitate when you oxidize ammonium tetrachloropalladate (+2) (PdCl2 + NH4Cl) to ammonium hexachloropalladate (+4) (tetrachloro + Cl).


I hope i got all the numbers right.... my eyes are getting heavy...


----------



## kadriver

The liquid did not settle and it was still very dark so I added some more ammonium chloride, added heat and stir.

It looks like more brick red powder came down.

I'll filter tomorrow and gather all the powder together.

kadriver


----------



## lazersteve

Sam,

I agree they appear different and behave slightly differently, but either way the end result is the colored powder is reduced to the metal by any one of several means.

Hoke's wording is very confusing indeed especially with her naming of the colored salt. Adding ammonium chloride to denoxxed solutions does not precipitate red Pd salt until the chlorine oxidizer is added.

Platinum salts commonly change colors (from green, orange, and yellow) as they are precipitated and purified further.

Steve


----------



## Lou

You've got the names right Sam; both are different and have different crystal structures (the diammine is octahedral and will wash better). 


I'll pull an ounce of the diamminepalladium (II) chloride and try this "wet calcination" by setting it up for reflux in a 1 L with saturated ammonium chloride solution. If I like it, I'll try it on production lot and we will publish a communication to the Platinum Metals Review AFTER we check to see if it's been mentioned. Is this something you came up with on purpose or just by serendipity? Grain size is very important to me. How things rinse is CRITICAL to purity and easy handling. 


Steve,

I agree that it is most confusing. The nomenclature back then wasn't really well defined with many things having common names or names of convenience. There was no really systematic method until IUPAC (which is hell on earth for complex molecules!!!!).


----------



## samuel-a

That was by chance Lou

I have noticed that when i was trying to wash yellow salt with boiling NH4Cl solution (1 mole) , the color went slightly darker upon gentle boiling.
From that, i deduced that decomp' must have occured and i knew the decop' temp' is quite low for yellow Pd. Some of it dissolved.

So the next trial was to boil as hard a i can, under reflux with saturated NH4Cl.
After 3 hours, The majority (i reckon about 95-98%) of the black powder clumped up ino tiny spheres that settled fast, the rest was as cloud of black powder that took several hours to settle.
I have noticed only very slight coloration of the solution from dissolution.

---------------------------------------
I'm very ashamed for not keeping better lab records, but that just the way i am...

I hope you could repeat the process with sucsess. I'm sure that with your knowledge, you could fine tune it far better then i ever could.


Edit: i will also try this with Pd-DMG.


----------



## lazersteve

I did a little digging in my CRC Handbook of Chemistry and Physics 55th Edition and found that the *colorless*, tetragonal palladium salt (tetra-ammine palladium (II) chloride Pd(NH3)4Cl2.H2O) decomposes at 120C when heated.

The palladium salt ( Pd(NH3)2.Cl2 ) dichlorodiammine palladium II trans or alpha) decomposes at an unspecified temperature when heated and appears as *yellow* tetragonal crystals. 

PdCl2 has a decomposition temperature as 500C.

Do you recall what temperature the reaction occured at? 

Steve


----------



## samuel-a

Yes Steve

At around 120-130C (reading from hotplate, not the solution it self), decomposition became noticeable.

I later ramped up the heat all the way up and left it alone. about two hours later there was no more signs of yellow. I kept it boiling for one more hour just to make sure.


----------



## RaoOvious

Kad keep ur visual sequential going....


----------



## kadriver

I filtered the powder from the last re-heating operation.

It yielded quite a bit of additional brick red powder.

I added this to the rest of the powder from the other filterings into a 600ml beaker and set up to add ammonium hydroxide.


----------



## kadriver

I did not know what kind of reaction to expect since this is my first time doing this.

When I opened the bottle of ammonia, the filter with a little of the damp red powder on it began to emit a white fume!

I added about 20ml of the 29% ammonium hydroxide and poured a small amount into 600ml beaker with the palladium brick red powder.

Then I stood back, because of the fumes, and watched the reaction.


----------



## kadriver

The reaction subsided quickly, so I added more ammonium hydroxide and stirred as per the instructions.

The flesh colored precipitate formed immediately and I stirred while adding more ammonia.

I quit stirring for a few minutes and the precipitate settled quickly to the bottom of the beaker.

I added more ammonia and looked for signs that the flesh colored precipitate was dissolving in the ammonia.

I kept adding ammonia and stirring, but the precipitate was not dissolving so I put it a the stir plate with no heat.


----------



## kadriver

I let it stir for about 30 minutes, then turned the stir plate off.

The precipitate began to settle out quickly so I added more ammonia.

I could not see where the flesh colored precipitate was dissolving.

I put it back on stirring and that is where I am at right now.

I have added about 300ml of the cold concentrated ammonia so far.

More to follow.

kadriver


----------



## Lou

It will dissolve, you may need to heat it. 


The white fumes are ammonium chloride produced from residual HCl in your ammonium hexachloropalladate.



Lou


----------



## kadriver

Thanks Lou, I added a little more ammonia and put it on to stir with a little heat.

I noticed the beaker that holds my glass stir rod had a nice yellow crystal looking powder form that looked like the powder I am trying to make here.

I don't know if this yellow powder in the stir rod beaker is the right stuff or not.

I stopped the stir for about 5 minutes and allowed everything to settle just to get a bearing.

Then I added a few more ml of ammonia and placed on low heat and stir.

The color of the precipitate looks almost like Bazooka Joe Bubble gum.

I'll keep heating and adding ammonia until the precipitate dissolves completely.

kadriver


----------



## freechemist

Seeing this topic to grow enormously into a big discussion, centering mainly on aqueous Pd-chemistry, I can not refrain from adding some comments from my own experience with palladium recovery/refining.

The biggest difference between what is stated in Hokes book about precipitation of (NH4)2PdCl6, ammonium-hexachloropalladate(IV), and the experiments done by kadriver, is the fact, that Hoke refers to Pd, mainly dissolved in an excess of aqueous HCl (originating from AR, used to dissolve), whereas kadriver starts with a more or less concentrated nitric acid solution, supposedly not containing any chloride. In Hokes case chloro-complexes of Pd, mainly PdCl42-, are already present, and thus, Pd(II) is easily oxidized with chlorate/HCl, to Pd(IV), forming finally the complex anion PdCl62-, which can be precipitated as red, sparingly soluble (NH4)2PdCl6 by addition of an ammonium salt, preferrably ammonium chloride.

In kadrivers case chloro-complexes of Pd have first to be formed, what apparently is done by addition of NH4Cl. In order to precipitate (NH4)2PdCl6 at least 4 moles of NH4Cl are used up to form the complex anion PdCl42-, and at least two moles more chloride are used, to form Cl2, to oxidize Pd(II) to Pd(IV), leading to the complex anion PdCl62-. Nitric acid alone is a weaker acid as HCl, and is also a stronger oxidant in presence of another, stronger acid, like HCl in AR. Thus, oxidation of Pd(II) to Pd(IV) gets easyier in presence of an excess of HCl.

In the discussion the danger of explosive NCl3-formation on use of NH4Cl and NaClO3 is mentioned. This can easily be overcome by using KCl in place of NH4Cl. In my hands K2PdCl6 has never been much more soluble than (NH4)2PdCl6, so I recommend to use KCl in further experiments.

Dissolution of metallic palladium in nitric acid or mixtures of sulfuric/nitric acid is not a simple reaction as it looks like, leading to solutions of PdSO4 and/or Pd(NO3)2. Reduction-products of HNO3 remain bound to Pd(II) tenaceously, even on prolonged, strong heating. This can well be seen by dissolving Pd-sponge/black in 62% sulfuric acid by adding only a small excess of nitric acid, in order to oxidize Pd(0) to Pd(II), where only small amounts of brown NOx are formed. Adding such Pd-solutions to refluxing aqueous HCl leads to final evolution of copious amounts of brown fumes, forming the known solutions of H2PdCl4.


----------



## Lou

KCl is great for Pt and Pd both because a large excess can be added to suppress the solubility without fear of causing a huge headache in waste treatment like ammonium chloride.

We will not use it in our processes because we calcine our salts and KCl is exceedingly difficult to remove from them. It also hazes the quartz reduction equipment by causing devitrification.

If you use hydrazine or formate, go for it.


I've never made NCl3 (unintentionally) during palladium precipitation. It will not form at the low pH of 2+ M HCl solutions.


----------



## kadriver

As you can see, I added more ammonia and heat on the stir plate.

This precipitate does not seem to want to go into solution - so far I have added nearly 400ml of 29% ammonia.

I placed the beaker on my deck with a plastic bucket and cinder block on top for the evening.

Tomorrow I will continue trying to get the flesh colored (more like bubble gum) precipitate to dissolve.

Is it possible I have dissolved all that can be dissolved?


----------



## kadriver

The precipitate has been stirring in the ammonia for about 5 1/2 hours now.

Does it take this long for the precipitate to dissolve?

kadriver


----------



## lazersteve

I have performed the purification of the red Pd salt many times. It typically takes less than one hour depending on batch size. I always used 10% NH4OH. Perhaps you need a little water to get things into solution. I would dilute the 28% ammonia (aqua ammonia) down to 10% with distilled water before adding. I agree with Lou, managing waste solutions containing ammonia can be a real headache. 

Another thing I've always done was to filter off the initial ammonia solution and add a fresh 10% ammonium hydroxide solution after I obtained the pink Pd salt. Alternately, filter out the pink salt and dissolve it in potassium hydroxide solution, then acidify with HCl to produce the potassium Pd salt mentioned by the others.

Freechemist,

I'm glad to see you joined the conversation, you input is greatly appreciated.

Steve


----------



## kadriver

I'll add some distilled water and see if that helps.

Also, I'll stop by Ace Hardware and get a gallon of 10% ammonia.

Thanks for the help.


----------



## kadriver

I started by filtering off the ammonia solution from the pink precipitate.

I then diluted some of the strong ammonia; 200ml distilled water with 100ml 29% ammonia.

I added it to the remaining pink precipitate and placed on the hot plate stirrer with low heat.

I transfered the filtered liquid to a 1 liter beaker and placed on low heat to drive off some of the ammonia.


----------



## kadriver

I heated the filtered liquid (the light green colored liquid in the 1 liter beaker) and some of the solution evaporated.

Also, a thin film of white material crashed out on the botom of the 1 liter beaker and some white material was floating on top of the solution.

I may have left it on the heat too long.


----------



## kadriver

I drew some of this liquid up with a pipette and placed it in a test tube


----------



## kadriver

I then took up about 1/2 ml of hydrochloric acid in a new pipette and began to add it to the solution in the test tube.

Lots of fumes were being produced (probably ammonium chloride).


----------



## kadriver

Suddenly, and quite beautifully, the bright yellow precipitate began to form.

It was a moment of triumph for me. 

I had been waiting for the flesh (pink) colored precipitate to dissolve completely.

The whole time there was palladium salt in this filtered liquid.

I am dissolving more of the flesh colored precipitate in more ammonia.

I will continue to dissolve the flesh colored material until no more yellow precip forms after adding HCl.

I will acidify the remaining liquid and post more pictures later.

kadriver


----------



## kadriver

I filtered the main solution to rid it of the white material that formed after heating and then added a few drops of hydrochloric acid.

There was a cloud of white fumes around the beaker as I added the acid.

After adding more acid, a few ml at a time, the solution started to turn color and bloom into the bright yellow precipitate.

I added about 30ml of hydrochloric acid to get this much precipitate.


----------



## kadriver

I filtered the liquid to seperate the yellow precipitate.

I used hydrochloric acid to rinse the yellow from the beaker into the funnel.

Then I removed the filter and opened it up to allow it to dry.

This is as far as I got today.

Once dry, I will put it in a quartz dish and burn off the ammonium chloride to form the palladium sponge.

kadriver


----------



## samuel-a

> Did not know what to use to rinse the beaker into the funnel



Cold dilute NH4Cl solution.

The yellow Pd is slightly soluble in conc' HCl, hence the noticable coloration of your filtrate (or, you just had a decent amount of Pt in the original material that made it through to this step).
If no Pt is present, the color usually should be much lighter and the solution holds very little dissolved Pd after precipitation. Somethims it is almost colorless.
I take pH down to 7-8 before filtering. Then wash with NH4Cl.


----------



## kadriver

Thank you samuel, I did not know how much HCl to add, or if I could add too much.

Since you clarified that the yellow salt is soluable in concentrated HCl, then my question is answered.

Next time I will use dilute HN4Cl (ammonium chloride) for the rinse and wash.

kadriver


----------



## lazersteve

I've always rinsed the yellow Pd salt with cold water.

Steve


----------



## Lou

Why not filter to remove the green?


----------



## kadriver

lazersteve said:


> I've always rinsed the yellow Pd salt with cold water.
> 
> Steve



The yellow palladium salt is no longer soluable in water? This means it could be washed several times in cold water.



Lou said:


> Why not filter to remove the green?



I did filter the green liquid through the same filter I had been using for all the other filterings (after I began dissolution in ammonia).

Lou: How should filtering to remove the green be accomplished? Just run it through a fine filter paper?

kadriver


----------



## Lou

First and foremost, you should follow 4metals's procedure to the T. It is EXACTLY how it's done. Nickel, copper, and cobalt (and other PGMs, for that matter) all form very soluble ammine complexes at higher pH...so it's important to drop the pH between 8.8-10 and filter again, then slowly acidify. You are working with already quite pure material. That material could be a nickel or other transition metal hydroxide and the green could be its ammine complex. Or it could be a small amount of Magnus's green salt (which looks quite similar).


Every salt is soluble in water--it's just a question of _how_ soluble. That is a product of its thermodynamic solubility constant Ksp.

For example: AgCl(s) --> Ag+(aq) + Cl- (aq) , the Ksp is 1.77×10-10

[Ag+ (aq)][Cl- (aq)]/[AgCl(s)] ; since solids are held to have an activity of 1, that denominator disappears ...


http://en.wikipedia.org/wiki/Solubility_constant

As you'll see, it's really a mixed bag of tricks and has much to do with the state conditions for the solvent (polarity, temperature, so on). 

In the case of palladium diammine (II) chloride, it's solubility is more affected by the reverse reaction (hydrolysis) of the salt back into that from which you have made it. It is an equilibrium but still shifted to favor that rather than its tetrammine complex which forms at higher pH and higher concentrations of [NH3 (dissolved)]


----------



## lazersteve

Lou,

Is this the method outlined by 4metals that you are referring to?

Cleaning Up Palladium

Steve


----------



## kadriver

Drop pH and refilter - got it.

This is all new to me and there is much more chemistry involved.

For now, I will just have to rely on the experience of the forum members.

I read the post "Cleaning Up Palladium" by 4metals and I would not even know where to get de-ionized water.

We used an ion exchange resin bed to purify feed water for the boilers when I was in the Navy.

Thanks for all the help so far.

I have the bright yellow salt on a filter paper and it has been drying for two days.

Today I am going to burn it in a quartz dish to get the sponge - I'll post some photos of that process.

kadriver


----------



## Lou

Go low on the heat!

And distilled water is roughly interchangeable with deionized.


----------



## kadriver

I calcined the yellow powder this evening - it took about 2 1/2 hours to get it all to convert.

I began by carefully transfering the yellow palladium salt to the fused quartz dish.

These things (fused quartz dish) are expensive - I paid $106 for two of them!

I used a pair of plastic tweezers to roughly break up the pieces of yellow powder.


----------



## kadriver

I placed the dish inside a corningware casserole dish and put the heat on medium high.

Nothing happaned at first so I bumped the heat up on high - then it started to smoke.

It was smoking pretty good so I truned the heat back down to medium high.

That turned out to be about right for this stage of the operation - a light smoke that was white and never turned color.

The photo is about 5 or 10 minutes into the process.


----------



## kadriver

The transformation was amazing to watch - it started to look a little burned.


----------



## kadriver

Slowly turing into metal


----------



## kadriver

Some parts of the dish appeared hotter than others, so I adjusted the quartz dish to get the heat where it was needed.


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## kadriver

A little over an hour - the smoke was very light so I turned up the heat a little bit.


----------



## kadriver

The reaction kind of stalled for a bit - I turned the heat as high as it would go.


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## kadriver

At 2 hours, some of the tips still had bits of color.

I placed another, larger, corningware casserole dish on top of the one on the hot plate to form a sort of oven.

I figured that my heat source was a little low for the final burning.

I hoped that the cover (formed by adding the larger dish on top) would compenaste and get the heat up to complete the process.


----------



## kadriver

Adding the cover dish helped get the operation complete.

Looks like it all burned after about 2 1/2 hours.

It looks good to me, but I am not sure how it is supposed to look.

It's off the the refiner on Monday - they said they would pay 90% of spot.

I will weigh it before then and post the weight before I sell the metal.

I can't believe I finally got some metal from all those cats I bought back in December.

I do not think I can thank you folks who guided me through the process enough!

But it's not over yet = there is still much to do.

kadriver


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## Rodthrower18

I'm really glad to see you pull some metal from this project my friend. It's at the perfect time to since there's been a good boost to prices here lately. How many cats did it take to get this amount? Did you do the pt yet, or were you focusing on on PGM at a time ?


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## lazersteve

Great job Kevin!

The Pd should be light gray like ash. It should be free of colors like orange, yellow, white, and rainbow hues. I like to hit mine with the hydrogen torch and clinker it up a bit without fully melting so it forms a tight consistent mass that is easy to handle. 

Steve


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## Lou

Aside from the obvious oxygen contamination, the Pd will be over 9995 pure.


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## kadriver

Pretty close Lou - the XRF was 99.92

But I don't know if it was melted in a new crucible or a used one.

I was very pleased with the result, and there was more metal than I though.

The weight was 2.9 DWT or 4.5 grams.

They let me take a picture after melting since it was my first palladium refining.

I don't know what kind of heat was used to melt the button - forgot to ask.

When I seen three nines on that statement, I kind of drifted for a bit - like walking on a cloud!

kadriver


----------



## Lou

Cool. Don't see any melt loss on it! Guess they're making enough money at 90%.

Just remember that it's an XRF that's calibrated for buying gold and gold alloys not for certifying palladium. It doesn't know any better.
Also, it's very important that you always weigh your own material before you ever take it to NTR or any refiner for that matter. One of the most important things to do to get peace of mind is to weight your material. It sounds like "more than I thought" meant that you took your hard earned button there without weighing it.

Now just do 4500 dwt, you've got it down.



I attached a photo of some buttons I made earlier this year in a zirconia crucible. They're meant to be used for making a heel for induction melting. 
Look at how gassy they are, just like that small one you see. They were produced just the same fashion as you did yours (at least as far as the refining step goes).


Lou


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## kadriver

Rodthrower18 said:


> I'm really glad to see you pull some metal from this project my friend. It's at the perfect time to since there's been a good boost to prices here lately. How many cats did it take to get this amount? Did you do the pt yet, or were you focusing on on PGM at a time ?



I should have kept better records - I do not know the numbers you are asking about Rodthrower18.

So far, I have been extracting each metal one at a time. I was going to save the palladium solution for later.

Since instructions was being offered, I decided to go ahead and refine the palladium before moving on to the Pt & Rh.

Glad I did, I gained much knowlege and experience.

I still have some palladium left in the solutions, plus another ammonia extraction from the flesh colored precipitate (but I don't expect much from that).

I still have the rest of the black powders (Pt & Rh) to process.

I need to do another dilute nitric treatment on the remaining black powders until I get a clear solution to ensure all the palladium has been removed.

The photo below shows the color of the second dilute nitric acid treatment (flask marked Pd Nitric) - very light in color.

I have rinsed the remaining black powders with tap water, but on the third rinse, the solution will not settle.

There is still some black suspended in the rinse liquid - it has been 6 days since I did the last rinse, and it has yet to settle - see the photo.

I guess I will just have to wait longer until it settles completely before I can proceed.

The remaining black powders (Pt & Rh) on the bottom of the tall beaker = about 1/8 inch deep.

kadriver


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## RaoOvious

Great Kevin,well done nd keep it up...


----------



## Lou

What makes you think that it will ever settle?


----------



## kadriver

Lou:

You are right - I did not weigh the material before I took it in.

This was my first time handling this kind of material.

I was scared to touch it - it seemed like a light breeze would have blown it all away.

I put the metal, still in the dish, in an envelope and carefully laid it on the floor of my car.

I gave them the metal still in the dish.

I begged for cautioned as it was a fused quartz dish (expensive).

I asked if they were going to melt it and they said, "first we got to figure out what it is."

From their reaction, it looks as though they don't see much pure (home refined) PGM metal coming in to them.

I'll make sure and weigh it before I let them have it next time.

I'll just fold a piece of paper, weigh the paper, tare the scale, and pour the palladium sponge on the paper to get a weight.

I was very, very pleased with the results I got - many thanks to you and lazersteve for the help you provided - you guys are the best!

kadriver


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## jimdoc

kadriver said:


> I'll make sure and weigh it before I let them have it next time.
> kadriver




Couldn't you have weighed the whole dish, and then weigh it after you get it back and cleaned it?
At least that would give you an idea of what you had.

Jim


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## kadriver

Lou said:


> What makes you think that it will ever settle?



Possibly lack of knowlege.

Is there a reason for me to conclude that it will never settle?

By the way - NTR informed me that they do not buy Rhodium.

kadriver


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## kadriver

jimdoc said:


> kadriver said:
> 
> 
> 
> I'll make sure and weigh it before I let them have it next time.
> kadriver
> 
> 
> 
> 
> 
> Couldn't you have weighed the whole dish, and then weigh it after you get it back and cleaned it?
> At least that would give you an idea of what you had.
> 
> Jim
Click to expand...


Jim;

Thats a good idea - I didn't think of it.

kadriver


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## freechemist

*@kadriver:*

Judging some of the fotos taken from your very first precipitation experiments to prepare (NH4)2PdCl6, I would say, that the rather brown precipitates in a more or less intensly brown coloured solution are actually crystallized (NH4)2PdCl4. The ammonium salt of the complex anion PdCl42-, like the potassium salt of the same anion, is not very soluble in concentrated ammonium- or potassium-salt solution, and can be crystallized (not quantitatively) easily by adding concentrated NH4Cl- or KCl- solutions to solutions containing significant amounts of dissolved PdCl42-. Both salts, (NH4)2PdCl4 and K2PdCl4 form brown, needle-shaped crystals and brown aqueous solutions.

*@lazersteve:* 

The abbreviated formula for the yellow precipitate obtained by adding dimethylglyoxime-solution to Pd containing solutions is Pd(HDMG)2, not Pd2DMG. Dimethylglyoxime, chemical formula C4H8N2O2, abbreviated H2DMG, is an organic molecule with two acidic protons, which first forms a mono-anion, HDMG- and then, in strongly alkaline solution, a dianion DMG2-. The yellow insoluble complex Pd(HDMG)2 is formally composed of a central Pd2+-cation, complexed by two HDMG-mono-anions, it's chemical formula being Pd(C4H7N2O2)2. This complex Pd-compound is uncharged and therefor behaves like an organic molecule insoluble in water. 

*Dissolution of Pd in HNO3:*

To dissolve Pd in nitric or nitric/sulfuric-acid mixtures in my practice I always assumed the following redox stoichiometry:
N(V) + Pd(0) ==> N(III) + Pd(II) or, only formally:
3 HNO3 + Pd(metal) ==> Pd2+ + HNO2 + 2 NO3- + H2O.
Nitrous acid, HNO2, the reduction product of nitric acid is a weaker acid, than HNO3, and can dissociate into a proton and a nitrite anion:
HNO2 <==> H+ + NO2-.
In presence of a much stronger acid HNO2 can also act as a base, being protonated to the unstable cation H2NO2+, which rapidly decays into water and a nitrosyl-cation:
HNO2 + H+ <==> H2NO2+ <==> NO+ (nitrosyl-cation) + H2O.
Finally NO+ and NO2- can combine to N2O3 (nitrous acid anhydride, N(III)-oxide), which disproportionates into a mixture of gaseous NO and NO2:
NO+ + NO2- ==> N2O3 (unstable)
N2O3 ==> NO + NO2 (nitrous gasses; NOx).


----------



## kadriver

freechemist said:


> *@kadriver:*
> 
> Judging some of the fotos taken from your very first precipitation experiments to prepare (NH4)2PdCl6, I would say, that the rather brown precipitates in a more or less intensly brown coloured solution are actually crystallized (NH4)2PdCl4. The ammonium salt of the complex anion PdCl42-, like the potassium salt of the same anion, is not very soluble in concentrated ammonium- or potassium-salt solution, and can be crystallized (not quantitatively) easily by adding concentrated NH4Cl- or KCl- solutions to solutions containing significant amounts of dissolved PdCl42-. Both salts, (NH4)2PdCl4 and K2PdCl4 form brown, needle-shaped crystals and brown aqueous solutions.



freechemist:

I am not a chemist, and I am trying to decipher what you have written.

I can see, from your description above, that by adding saturated NH4Cl to the concentrated/reduced pd/nitric solution, I made an ammonium Pd salt (II) instead of a Pd(IV) and the Pd(II) is not very soluble in concentrated ammonia.

This would explain why there is much pink-flesh colored material left in the reaction vessel after adding so much concentrated ammonia.

I used concentrated HNO3 to dissolve the Pd from the mixed black powders that I started with.

If what I have written above is correct, and the 6 salt is more soluable in concentrated ammonia, then is there a way to avoid the formation of the Pd(II) salt, and get it to form the Pd(IV) salt?

I have more black powder to process for Pd and this information would be helpful for that future operation.

I want to take some chemistry classes, I had nine math classes for my BS in management, but no chemistry.

I know I have the ability to understand chemisrty. What I lack, until now, is the *desire to learn it*.

I can see acutely where having the knowledge would be helpful in refining - especially platinum group metals.

In college, the math professors taught on a chalk board with a piece of chalk in one hand, and an eraser in the other.

Pretty soon I learned to just tune the professor out, and work the example problems in the text book during class.

Essentially, I taught myself advanced mathematics including Algebra, Stats, and Trig.

I aced the Trig mid-term and the professor said, "The final is just more of the same" and he exempted me from the final and gave me an "A" for the class - true story. He thought I was a "Nuc" from one of the subs down on the waterfront - not.

Can anyone recommend a good chemistry text book that would facilitate the type of learning I described above - I know some texts are better than others.

You see, now the forum has driven me to improve my education - this is a great place to be!

kadriver


edit by Lou: kadriver, I changed the valence of the Pd as appropriate just so others are confused and there's more continuity. I changed 4 to Pd(II) and 6 to Pd(IV).


----------



## freechemist

Please let me add some last comments.

*@samuel-a:*

All Pd-compounds mentioned in this thread are coordination compounds. A coordination compound is composed of a central atom/ion, surrounded by a certain number of nearest neighbours, the ligands. The center, in this thread Pd, can exist in different oxidation states, namely +2 (Pd(II)) and/or +4 (Pd(IV)). The number of ligands around the center determines the coordination number. Most Pd(II)-coordination-compounds are composed by a central, formal Pd2+-ion, symmetrically surrounded by 4 ligating atoms/ions in a square-planar arrangement. The coordination number of the central Pd(II) is 4. *Examples:* Pd(NH3)42+, (NH3)2PdCl2, PdCl42-. Pd(IV)-coordination-compounds usually have a formal Pd4+-center, symmetrically surrounded by 6 ligating atoms/ions in an octahedral arrangement. The oxidation-number is +4, the coordination-number is 6. *Example:* PdCl62- in the salt (NH4)2PdCl6.

*Formation of Pd-ammine-complexes:*

Simple ammine-complexes of Pd(II) are formed by mixing Pd(II)-solutions with aqueous ammonia. These can be solutions of Pd(II) in diluted HCl, HNO3, H2SO4 and others. In excessive ammonia the tetrammine-palladium(II) ion, Pd(NH3)42+ is finally formed. In case of HCl a pink coloured, only sparingly soluble salt, composed of Pd(NH3)42+-cations and PdCl42--anions, precipitates intermediately, whose elemental composition is exactly the same as that of the also sparingly soluble, yellow diammine-palladium(II)-chloride (NH3)2PdCl2. This same yellow compound is also formed on lowering the pH-value of a [Pd(NH3)4]Cl2-solution to about 3-4 by means of diluted HCl. In this reaction two of the totally 4 ligating NH3-molecules are protonated to NH4+ and replaced by chloride anions, leading to the non-electrolyte (NH3)2PdCl2:
Pd(NH3)42+ + 2 H+ + 2 Cl- <==> (NH3)2PdCl2 + 2 NH4+.
On treating solid, red (NH4)2PdCl6 with excessive aqueous ammonia, Pd(IV) is reduced to Pd(II), followed by final formation of a tetrammine-palladium(II)-solution, probably according to the following redox-stoichiometry:
3 Pd(IV) + 8 NH3 ==> 3 Pd(II) + N2 + 6 NH4+
Hence also the fumes observed by kadriver.


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## samuel-a

Thank you freechemist.
Very informative !


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## RaoOvious

kadriver said:


> If what I have written above is correct, and the 6 salt is more soluable in concentrated ammonia, then is there a way to avoid the formation of the Pd(II) salt, and get it to form the Pd(IV) salt?



Kad Here is an additional procedure to the method(Lou's) employed by you specially for avoiding the formation of sparingly soluble brown colored (NH)4PdCl4(Ammonium terachloropalladate) as elucidated chemically by freechemist.

1)Get the palladium dissolved from mixed Blacks by nitric washes until it doesn,t change color.Use minimum nitric and when each nitric wash gets brown or less brownish or yellowish,as washes proceed,add distill water and let it sit for a while to settle the remaining blacks,then filter each nitric wash into a separate beaker(B),any unsettled blacks would get trapped into the filter,and u can rinse them with wash bottle into the original beaker(A) containing mixed blacks.

2)Once you have got all the nitric washes into the beaker B,cement the Palladium with zinc turnings(as per Steve) from Palladium Nitrate deep brown solution until it gets clear in color,make sure to test with SnCl2 or DMG.Once all the palladium black with possibly minute contaminants(below zinc's reactivity) gets cemented,decant the above solution just as u had did in initial cementation of mixed blacks.Now rinse the palladium blacks with water to get rid of free nitric.

3)Treat the washed pd blacks with dilute HCL or 20% NAOH to get rid of zinc,as you did earlier.

4)Once your palladium black gets rid off zinc,its preferred that you dry and weigh it then otherwise.Then add 5ml of AP per gram of blacks(9:1,HCL:H2O2).The palladium blacks would dissolve within few hours,boil down the palladium chloride solution to get rid off free chlorine and also concentrate it to syrupy form,Put concentrated solution of NH4CL,if any platinum is there it would precipitate as canary yellow (NH4)2PtCl6.Filter the canary yellow platinum salt and save it to add to your platinum batch later.Now bubble chlorine to the filtrate solution(lots of alternatives for chlorine generation) to get Ammonia soluble brick red [(NH4)2PdCl6 Ammonium hexachloropalladate(II)] palladium salt,You know the next steps...Its ammonia treatment would dissolve all the flesh colored palladium salt into the ammonia solution.Then filter and re acidify with HCL,get ur bright yellow palladium salt(Diammine Dichloro Palladium II ),Calcine it and.......

Rao


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## freechemist

*@kadriver:*

Please excuse me, if I wrote somewhat cryptically for you. By extracting some statements from your last post, I try to clarify things a little.

"_I can see, from your description above, that by adding saturated NH4Cl to the concentrated/reduced pd/nitric solution, I made an ammonium Pd salt (II) instead of a Pd(IV)_"

This is what I suppose you having done by adding saturated ammonium chloride solution to the aqueous nitric acid solution of palladium. The dissolved Pd2+ ions reacted with chloride to form the complex anion PdCl42-, which, in presence of a fairly high ammonium concentration, crystallized partially as solid, needle-shaped, brown (NH4)2PdCl4. Solely with nitric acid Pd(II) is not oxidized to Pd(IV). A stronger oxidant must be used (e.g. Cl2, generated out of chlorate/hydrochloric acid). This is also evident by the fact, that dissolution of Pd in AR results in a solution of H2PdCl4, not H2PdCl6.

"_Pd(II) is not very soluble in concentrated ammonia_"

(NH4)2PdCl4 reacts with ammonia as well as (NH4)2PdCl6, albeit less vigorously, than the Pd(IV)-compound. The same is true also for the potassium salts K2PdCl4 and K2PdCl6.

"_This would explain why there is much pink-flesh colored material left in the reaction vessel after adding so much concentrated ammonia_".

Heat and stir the pink suspension constantly near it's boiling point by adding small amounts of concentrated ammonia solution from time to time until all pink solid has dissolved.

"_If what I have written above is correct, and the 6 salt is more soluable in concentrated ammonia, then is there a way to avoid the formation of the Pd(II) salt, and get it to form the Pd(IV) salt?_"

Formation of the Pd(II) salt has not to be avoided. It is a step on the usual way to refine palladium. However, Pd-refining may be more efficient by first precipitating Pd(IV) under oxidizing, acidic conditions, separating the solid hexachloro-palladate(IV) and refining Pd further by reacting it with aqueous ammonia to a solution of Pd(NH3)4Cl2, which can be purified by filtration and then by slow acidification in order to precipitate the sparingly soluble non-electrolyte (NH3)2PdCl2.

"_I have more black powder to process for Pd and this information would be helpful for that future operation._"

For future operation I recommend the following procedures:

1.) Collect and let dry more of the black powder. Before working it up further always weigh the material to be treated.
2.) Dissolve it in HCl/H2O2 or HCl/NaClO3 by heating the material in the required amount of 32% HCl, diluted with half it's volume water, by adding the oxidant (e.g.35% H2O2) to the constantly stirred and moderately heated (ca. 70oC) suspension in small increments.
3.) Try to hold the total metal-concentration (Pd+Pt+others) at 50-75 grams per liter.
4.) To precipitate a solid hexachloro-palladate(IV) use KCl in place of NH4Cl.


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## kadriver

Great info from everyone.

I'll print these instructions and add them to my reference library at my shop.

Lou - thanks for changing the valence numbers.

I took a picture of some of the red powder that was left in a small beaker.

I added distilled water to it expecting it to dissolve so I could add it to the Pd rinse water/stock pot.

It partially dissolved evidenced by the yellow color of the water.

But some of the red powder did not dissolve in the DH2O.

Some of this red powder - precipitated from nitric/Pd solution with saturated ammonium chloride - is insoluable in water.

One day I will understand what this material is - but for now it is a mystery.

kadriver


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## kadriver

Today I did another dilute nitric acid treatment on the remaining mixed black powder - this is the third time.

Before I started, I decanted the liquid to a seperate container (see in the back ground of the second photo).

The nitric acid turned yellow again - looks like more Pd removed - I will test with DMG tomorrow and then check for dissolved Pt as before.

kadriver


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## RaoOvious

Kevin,keep it going...


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## Palladium

That man has come a long way! Seems like yesterday he was trying to figure out the silver cell. Look at him today. My hat's off to you Kevin.


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## kadriver

Thank you palladium.

I have given a third and forth nitric treatment to the remaining black powders.

I have yet to get a clear nitric treatment - that is what I am trying to achieve so that I can move to the next step in Lou's abreviated process.

I belive the next step (once I get a clear nitric acid boil) is to remove the rhodium with concentrated sulfuric acid.

I hope I am not dissolving platinum with each of these nitric acid treatments.

I had to pause with this as I am cementing more mixed black powders from some HCl/Cl leach liquid - I've got about 6 or 8 more gallons to go.

Plus I had a batch of silver and gold to process that took some time away from the PGM work.

Then there is more leaching to do.

I'll post a picture of the 4th nitric treatment of the original 10 grams of mixed black powders that I started this post with - tomorrow.

kadriver


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## kadriver

Here is a photo of the 4th dilute nitric acid after a vigorous boil for an hour.

The color seems to be getting darker instead of lighter.

I drew some of the solution into a tube and added DMG - obviously still some Pd, but not much.

I allowed the Pd/DMG precipitate to settle, then drew off some of the clear liquid.

I put 5 drops of this clear liquid in well "A" on the spot plate, and 5 drops in well "B" on the spot plate.

I then added 3 drops of stannous chloride to well "B".

At first there was no change, then after a few seconds I could detect a faint orange color.

It looks like there is some platinum dissolving during these nitric acid boils.

I'm not getting the desired result - I'll just keep boiling in dilute nitric until I get a clear nitric solution (indicating there is no more Pd to dissolve).

Any input would be helpful - I don't know if I am on the right track with this remaining black powder.

kadriver


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## lazersteve

Kevin,

After reading back through the posts, I see you are using diluted nitric acid. Lou's instructions call for concentrated nitric acid, perhaps this will allow you to complete the Pd extraction so you can move on to the next step. Stirring may also assist in the removal of the remaining Pd. The color of the extracted solution is starting to look more like a Pt solution than a Pd one to me. This could be the result of trace chlorides in your water and nitric acid dissolving some of the Pt.

Steve


----------



## Lou

Very fine Pt can dissolve in nitric acid, so I've been told.


I do not know if it is a phenomenon of chloride traces or if it is a phenomenon of just the nitric acid. The engineer who works with me says he has seen it on Pt black.


----------



## kadriver

I concluded that the spot plate tests look like Platinum too, since the stannous test turned orange.

Just goes to show how these platinum group sister metals like to travel with each other.

I will do a concentrated nitric treatment on the remaining blacks to see if I can get the last bit of Pd out as per Steve's recommendation above - but it looks like a 100% extraction may not be possible.

So far I have about 400ml of dilute nitric decanted and stored for future use from these 4 nitric acid treaments.

On page 165 of Hoke, she describes an "alternative method" with nitric acid for the mixed black powders precipitated with zinc from the stock pot.

In the second paragraph on page 165, under the heading "ALTERNATIVE ACID METHOD FOR THE BLACK POWDER (STOCK POT CONCENTRATE)", she says to use diluted nitric, 1 acid with 2 water, and heat the mixed black powders "gently" for no longer than an hour to remove the palladium.

On page 166, she goes on to say that "a little platinum may dissolve with the palladium even under this gentle treatment".

I am treating with dilute nitric, 1 acid with 1 water, and doing a rapid boil for about an hour.

I will continue to do nitric treatments and test with DMG until I get either no yellow precipitate or very little of the yellow precipitate, post a photo of the test, then continue with the rest of the process.

It is starting to look like I might not get a clear nitric acid - no matter how many times I treat the remaining black powders.

These processes are all new and exciting - I am gaining much valuable experience, plus contributing to the forum.

I look foreward to the day I get to refine the pure platinum from these mixed black powders.

Thanks for the help!

kadriver


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## kadriver

One other thing to mention, I am going to use distilled water to do the washings of the remaining mixed black powders.

I had been using tap water - but this may contribute to some chlorine being present and forming a small amount of aqua regia when the nitric acid is added and causing some Pt to dissolve.

Thank you - kadriver


----------



## kadriver

I performed a 5th nitric acid treatment today on the remainingn mixed black powders using hot concentrated nitric acid (with a few ml of distilled wash water left on the black powders).

After heating for about 1 hour, and once the solids settled (about 3 hours later), I drew off some of the nitric solution and added it to a test tube - about 2ml along with 3 or 4 ml of distilled water.

I heated my DMG test solution to dissolve all the DMG crystals that had formed and added about 3 or 4 ml of DMG test solution to the diluted nitric solution in the test tube.

There was absolutely no yellow precipitate formed - I concluded that all the palladium has finally been removed.

I did a spot plate test on this same solution and got a very very faint orange color - probably a little platinum dissolved from the hot nitric acid treatment.

I am going to decant this acid and and save it for later treatments of palladium removal.

I'll then wash the remaining black powders until I get a neutral pH to ensure all the acid has been rinsed and go to the next step in the process - treating the remaining black powders with concentrated sulfuric acid to remove the rhodium.

Comments and ctritique welcomed and invited - thanks for looking.

kadriver


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## RaoOvious

Good work as usual kad,I think for your next batch Lou's Methodology should be changed a bit as he himself explained that some platinum can dissolve when in black.

Logical change to Lou's Method would be to remove the Nitric washes' step and directly do hot concentrated sulfuric acid washes,which would remove both palladium and rhodium(plus BM) until it gets clear,u would have almost pure platinum left as blacks(Rest as usual),the dissolved Pd and Rh can be again cemented with zinc,then do nitric washes until all the palladium gets dissolved,I think u can handle rest of the art....


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## kadriver

RaoOvious - I have read through both of your suggested processes - several times.

They look straight forward and easy to follow.

But for now, I would like to stick to the plan and continue to follow the process that I have already started.

Freechemist has also offered some good suggestions - but I must resist the temptation to deviate to one of these new processes and stick to the original plan.

I have printed these instructions and added them to my reference library at my shop.

In the future, I may start a new thread and use one of these alternate processes.

Thank you - kadriver


----------



## kadriver

Here is a shot of the remaining black powders - should be rhodium and platinum - most of the palladium has been removed with nitric treatments.

The photo is of the 5th rinsing using distilled water - the pH is between 6 and 7.

Each time I rinsed the remaining black powders, I have had to wait for at least 2 days for the suspended black powders to settle.

I am trying to achieve neutral (pH of 7).

I have a small beaker of distilled water sitting nearby.

I take a pH test strip and tear it into two pieces.

I then dip one of the pieces of pH test strip into the distilled water sitting nearby, and the other piece into the beaker with the Rh, Pt, and rinse water.

Then I compare the two pieces of test strip with each other and with the color standards printed on the pH test strip package.

Once I get an absolute neutral (pH 7) I will decant the last bit of rinse water with a pipette (thanks for that tip *butcher*).

Once all the water has been decanted that can be removed with the pipette, I will evaporate the remaining moisture with low heat so the black powders will be completely dry.

then I'll add concentrated sulfuric acid to start the rhodium removal.

A question please; is there any reason or benefit associated with incinerating the remaining blacks to redness before I add the sulfuric acid?

Also, what would happen if there was some residual nitric acid present when I added the sulfuric? Would this cause a problem later in the process? Is it essential to remove every last bit of nitric acid with water washes before adding the sulfuric?

Hopefully I can get to the sulfuric acid treatments after two more distilled water washes - but at the rate of two days of settling per wash, I am looking at about 4 more days before I can begin the sulfuric acid treatments.

Any inputs to correct any errors I may be making would be greatly appreciated.

kadriver


----------



## HAuCl4

Nice kitchen! 8)


----------



## Lou

It would be just easier to use dilute acid peroxide and dissolve the platinum that way. Or even dilute aqua regia. As long as it doesn't get very hot, it won't dissolve much of the rhodium. The sulfuric acid treatment works on rhodium black, but it requires a lot of heat and the fumes it makes are carcinogenic (SO3) and very disagreeable. I ought not to have recommended it. It is a great qualitative test for Rh though!


----------



## kadriver

Lou - thank you for the heads-up about those fumes - I have seen them from an overheated sulfuric acid pickling solution one time.

My goal is to get the platinum from the rhodium. I am not overly consumed with getting any of the rhodium.

My concern is this; by dissolving the powders with dilute AP or dilute AR, I'm bound to get some Rh in with my Pt.

I would like to end up with the nice yellow colored precipitate of the platinum salt (is it called Ammonium Hexachloroplatinate?) for calcining to platinum sponge.

Since I use a refiner who will melt it for me, I do not intend to melt any platinum or palladium myself. I'll let the big refinery do that for me.

Here is my plan/procedure;

I have a reflux condenser with ground glass connections.

My plan to remove the Rh from the Pt with sulfuric is to do the reaction outdoors with the reflux condenser in place to minimize fumes going into the atmosphere.

I will put some sand in a corningware casserole and place the round flask in the sand (not too deep) for heat distribution.

Once in place, I'll slowly add the concentrated sulfuric acid (with heat off) until it is all in the flask - about 150ml for the first reaction.

I'll do this with all the proper safety items, clothing, goggles, respirator.

Then set up the condenser and start the water flow via recirc pump in a 5 gal bucket of icewater, turn on the heat - and get inside the house and monitor from a nearby window.

Once it looks like the reaction is complete (judging by the fumes in the reaction vessel) then I will turn off the heat and leave the waterflow through the condenser until everything reaches room temp.

Carefully decant the acid/Rh solution and set it aside in a sealed container for cementing with zinc later on, then repeat until the acid is clear.

I need the money from the platinum as the material for refining gold and silver has dropped off like a ski-jump.

Plus I would like the benefit of the education provided by the experince, and to complete the process and complete this thread/post.

Once I have gotten all the PGMs from these cats, I am going to retire from PGM refining - much too involved and dangerous!

Thank you for all the help you have given - kadriver


----------



## Lou

It will be faster and more effective to use HCl and peroxide a la lazersteve or perhaps 3M aqua regia with slight heat. Sulfuric works, but you won't easily filter that solution and it is so colored you can't easily tell when solids go out.

Best,

Lou


----------



## kadriver

Lou said:


> It will be faster and more effective to use HCl and peroxide a la lazersteve or perhaps 3M aqua regia with slight heat. Sulfuric works, but you won't easily filter that solution and it is so colored you can't easily tell when solids go out.
> 
> Best,
> 
> Lou



OK Lou - I'll skip the sulfuric acid and go with HCl and peroxide at room temp for the digetion of the Pt - I have some 40% H2O2 bought from "Sallys Beauty Supply".

There is probably not much Rhodium in there anyway.

I have worked with sufuric acid from a gold stripping cell - I had to dilute the resulting acid from that cell with 20 volumes of water before I could filter out the black gold mud from the acid.

Once I am certain that all the nitric acid is out of the remaining black powders with pH test strips, then I will use gentle heat to drive off any moisture before adding the HCl.

I have a seperation funnel with a valve that can be adjusted to allow a slow drip of H2O2 into the container holding the Pt black and HCl on a stir plate with a stir bar.

I can set it up and start the drip, then get inside away from the chlorine gas generated by the drip. 

I guess that I will have to live with some Rh contamination in my platinum.

Or is there a Pt repurification process that can be used to remove the Rhodium in a different way - similar to the way that the palladium was handled earlier in this post?

kadriver


----------



## kadriver

Are there any spot plate tests that I can do to a small sample of the black powders that will selectively check for the presence of rhodium?


----------



## Lou

Stannous chloride would be one good indicator, but if there is even very slight Rh contamination, the solution left over from precipitating the ammonium hexachloroplatinate will be a vivid bright pink!


----------



## lazersteve

Here's some posts on Rh testing:

Rh Test Results Stannous

Rh Test Results Sulfuric Acid

Steve


----------



## Lou

FYI, the dilute "lazersteve" method of separating Pt from Rh and Ir works remarkably well. I call it the lazersteve method because I saw Steve employ it on some iridium containing med material and then saw the resultant platinum product. If time is not an issue, it is the pre-eminent way.

Low and slow!


----------



## kadriver

I am still waiting for the last distilled water washing of the remaining black powders to settle - it takes days for it to happen all the way.

I printed out the test for Rh provided by lazersteve - I did not want to disturb the washed powders until they settle completely - once settled, I'll do the test for Rh.

I'll search the forum for the dilute method you referenced Lou - thank you.

In the mean time, while waiting for the washings to settle, I went back to some of the palladium solutions left from the palladium refining.


----------



## kadriver

I forgot to post the picture of the distilled water wash of the remaining black powders.

Today is Wednesday, and the wash water was added Monday night and this is as far as it has settled since then.

I need a centrifuge to speed things up.


----------



## kadriver

Back to the palladium solutions;

Beginning with the large two liter beaker - it contained the wash water that was allowed to evaporate naturally to concentrate.

I began by filtering to remove any solids from the solution.

Then I prepared a saturated solution of dimethyl gloxime (DMG) to scavenge the palladium from the solutions.

I made the DMG solution by adding about 2 or 3 grams to 200ml of distilled water, then heating to near boiling to get the powder into solution.

I don't use any solvents when preparing my DMG solution - Just hot water seems to do nicely.

Once the Pd solution was filtered, I began adding the DMG to the filtered solution a few ml at a time.

The precipitate began to form immediately starting out as a yellow cloud in the solution, then getting much thicker.

As the precipitate settled, I noticed that the liquid was still quite yellow, so I added more hot DMG and more precipitate was formed.

Eventually, all the palladium DMG came out of the solution.


----------



## kadriver

The liquid above the precipitate became as clear as water so I concluded that all the precipiate had come down.


----------



## kadriver

I then filtered the precipitate and washed it with cold distilled water.


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## kadriver

I added a blob of the palladium DMG precipitate to the ammonia solution in the same beaker from the earlier palladium refining.

I was not sure if it would cause a vigorous reaction or not - but the reation was very low.

Using a pipette, I rinsed the precipitate from filter into the beaker with 10% ammonium hydroxide solution.


----------



## kadriver

The stir bar was still in the ammonia solution, so I placed the beaker with the newly added palladium DMG precipitate on the stir plate and added low heat.

After a minute or so on the stir plate, the whole thing turned redish pink colored - I hope I did not make a mistake here because I was not expecting that color.

this is as far as I got today - low & slow is the ticket. I still have the other palladium solutions to scavenge with DMG - more to follow.

kadriver


----------



## kadriver

After more stirring and more heat, I filtered the liquid to retreive the palladium solution.

After retreiving the valuable palladium dissolved in ammonia, I used 10% ammonia (from Ace Hardware) to rinse the solids back into the beaker for more stirring and heat.


----------



## kadriver

I placed the filtered liquid on the heat to drive off excess ammonia.

Some orange colored precipitate formed after an hour or so - it is just barely visible in the second photo below.


----------



## kadriver

After heating to drive off excess ammonia, I filtered the solution again to remove the slight orange precipitate.

The solution is now ready for acidifying with hydrochlic acid to form the bright yellow palladium precipititate.


----------



## kadriver

I added a few ml of 31.45% hydrochloric acid to the the filtered liquid.

The solution immediately turned cloudy, then the bright yellow precipitate began to form.

At first it did not look right - too light in color - almost a pale tan color on top and bottom with a band of yellow in the middle.

It looked as though I had made a mistake.

But after sitting for a while it turned bright yellow.


----------



## lazersteve

When purifying the Pd I have never seen any reason to drive off the excess ammonium hydroxide. I simply add enough HCl to acidify the mix and reform the yellow Pd salt.

The orange salt may be Pt, check a sample with stannous chloride to see.

Steve


----------



## kadriver

I filtered the precipitate to remove the liquid and washed multiple times with cold distilled water.


----------



## kadriver

Once all the liquid was gone from the filter, I removed the filter and placed on some paper towels to dry for calcining later on.


----------



## kadriver

I also had some palladium dissolved in ammonia from another extraction of the flesh colored precipitate from earlier in this post.

If you look back in the post, you will see where there was some flesh colored precip that did not completely dissolve during the ammonia treatment.

I added more ammonia (this time 10% ammonia from Ace Hardware), more stirring and more heat. 

I noticed that more of the flesh colored precip had dissolved after these additional treatments.

This is the liquid from those additional treatments - it has already been filtered to remove any solids.


----------



## kadriver

I heated the solution for about an hour to drive off excess ammonia, filtered again, then added hydrochloric acid to form the bright yellow precipitate.

I then filtered off the liquid and removed the filter with the precipitate and set it out ot dry for calcining.


----------



## kadriver

Here's the results of todays work.

Probably about a grams or a gram and a half of palladium (after calcining).

Not all that much metal, but a great learning experience for me.

I learned that the flesh colored precipitate, if fresh ammonia is added, will yield more yellow powder (filter paper on the left).

And I learned how to recover the yellow powder from the DMG scavenged precipitated dissolved in ammonia (paper on the right).

I did notice that the DMG side (right) has a two toned color to it - as opposed to the single solid color of the yellow powder on the left.

Thanks for looking - any critique or comments are welcomed - kadriver


----------



## kadriver

lazersteve said:


> When purifying the Pd I have never seen any reason to drive off the excess ammonium hydroxide. I simply add enough HCl to acidify the mix and reform the yellow Pd salt.
> 
> The orange salt may be Pt, check a sample with stannous chloride to see.
> 
> Steve



Steve - I'll remember this next time I do this. I did remember to use cold water to rinse the yellow powder this time. 

It worked perfectly with no visible yellow powder dissolving after adding cold distilled water.

The first time it did this part, I used hydrochloric acid to rinse the yellow powder - I did not realize that the yellow powder was somewhat soluable in HCl.

I did save the filter with the orange precip, I'll test it to see if it is indeed Pt.

Thank you - kadriver (Kevin)


----------



## kadriver

lazersteve said:


> Here's some posts on Rh testing:
> 
> Rh Test Results Stannous
> 
> Rh Test Results Sulfuric Acid
> 
> Steve



Steve:

I have never performed any testing for rhodium - Lou mentioned that sulfuric acid is a good qualitative test for rhodium earlier in this post

From reading the procedure for doing SnCl test for rhodium, it looks like I will need some rhodium in solution to perform the test (with no gold, platinum or palladium).

The only way I can see to get the Rh in solution is with hot concentrated sulfuric acid.

I'll take about .1 gram of the rinsed and dried black powder and carefully boil it in concentrated sulfuric acid in a test tube to get the rhodium (if any is there) to go into solution.

Then I will do the test on the sample to see if I can detect the presence of Rh with stannous chloride (SnCl).

I looked at the link for the sulfuric acid test - it showed a picture of a tube with a redish brown colored liquid, but I did not see a procedure for performing the test.

After the rhodium tests are complete, then I think I am ready to do a platinum extraction using HCl & H2O2 with the remaining black powders.

I believe that I have gotten all the Pd that I can at this point from the repeated nitric acid treatments of the original black powders that I started with in the beginning of this post.

I have begun to use distilled water for doing the rinses - tap water is sure to allow residual chlorides - this may cause a slight bit of AR to be formed when the nitric is added for the palladium removal step.

This would explain (at least partially) why some of the platinum dissolved during the nitric acid treatments - platinum is not supposed to dissolve in hot nitric - theoretically speaking.

Thank you for all the help provided - you guys are great!

kadriver


----------



## kadriver

I dried the washed powders of all moisture, then added 50ml of hydrochloric acid and 50ml distilled water.


----------



## kadriver

I moved everything outdoors and added some hydrogen peroxide - about 5ml - to the dilute hydrochloric acid.

This is my first time using HCl/H2O2 to dissolve platinum black powders - I expected some fizzing or bubling - but the reaction was practically non-existant.

Probably due to the small amount of material in the beaker.


----------



## kadriver

After about an hour I could see that some of the black powder had dissolved, the liquid looked deep red colored.

I added three drops from the beaker to the spot plate. Also three drops of platinum standard test solution.


----------



## kadriver

I added three drops of distilled water to each cavity containing the Pt solution from the beaker, and to the Pt standard test solution to dilute a little.

Then I added 1 drop of stannous chloride to each cavity.

I looks very dark red color - the camera does not show what it looked like in person.

I would say that it is a positive test for Pt, but I have never tested a concentrated Pt solution so I can not say for certain.


----------



## kadriver

I added 3ml more of H2O2 to the beaker, then set the beaker under a plastic bucket and put a weight on top.

I held it up to the light after adding the 3ml H2O2 and I could see tiny bubble being generated by the reaction.

I'll let it set overnight and check it in the morning.

Hopefully, only the Pt will dissolve, and all that will be left in the Rh (if any).

Thanks for looking - comments and critique welcomed.

kadriver


----------



## kadriver

Today I drew off the dissolved platinum to a clean beaker and placed it on the heat to evaporate excess liquid in preparation to precipitate the orange platinum powder with ammonium chloride.


----------



## kadriver

I evaporated the solution by about half.

I added ammonium chloride to about 200ml of hot water.

I kept adding the ammonium chloride and heating until no more would dissolve - it surprised me how much it took.

I did not keep track of the amount I added - I knew that it would be saturated when no more would dissolve.


----------



## kadriver

I slowly added the saturated ammonium chloride to the concentrated solution

[youtube]http://www.youtube.com/watch?v=2vkipKcZbTw&feature=plcp[/youtube]


----------



## kadriver

The color of the precipitate was not what I expected.


----------



## kadriver

I did not know how much ammonium chloride to add, so I added until no more precipitate appeared to form.

Then I filtered the precipitate out of the solution - I used the ammonium chloride to rinse the precip from the beaker into the funnel.

Edited once to add a photo


----------



## kadriver

I was surprised to see the filtered liquid was quite dark.

I was expecting the liquid to be nearly clear.


----------



## kadriver

I tested with stannous and got a positive for Pd - I was not expecting that!

I thought I had removed all the palladium with nitric acid treatments.

I tested with DMG and discovered that the solution was loaded with palladium.


----------



## kadriver

Here is a shot of the platinum salt that was precipitated with saturated ammonium chloride after the liquid was filtered off.

Edit one time to add a picture


----------



## kadriver

Since there was palladium in the solution, I decided to add sodium chlorate to see if the palladium salt would form.

The video posted above shows the sodium chlorate being added the the solution.

This is a shot of the resulting precipitate that formed, and what the solution looked like after adding the sodium chlorate.

The precipitate was black - again, not what I was expecting.


----------



## kadriver

Before filtering, I did a stannous test.

It was a very faint orange - A tiny bit of platinum still remained in the solution.

There was no indication of palladium with the stannous test.


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## kadriver

Something definately looks wrong here.

This was my first go at platinum, and these procedures are all experimental in nature.

I have no clue what that black material is.


----------



## kadriver

Here is what I collected in the filter -


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## kadriver

This is supposed to be palladium salts - but it does not look like any that I have seen anywhere on the forum or in any publication.

I must have made a mistake somewhere - but I did gain some valuable experience with all these experiments.


----------



## kadriver

Top left = palladium salt ready for calcining.
Top right = Palladium DMG salt, needs further treatment.
Bottom left = the black precip from the NaClO3 precip (supposed to be palladium salt).
Bottom center = sparingly ammonia soluble brown colored (NH)4PdCl4(Ammonium terachloropalladate).
Bottom right = platinum salt precipitated with saturated ammonium chloride.

kadriver


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## RaoOvious

Looks like u have also dissolved and thus precipitated Rhodium along platinum thereby causing the platinum precipitate to have a greenish look instead of of fine canary yellow.


----------



## kadriver

I agree - the platinum salt did not look very clean, but there is a procedure to repurify - I'll try that to see if I can get it clean.

What really baffled me was the amount of palladium that was still there.

I did 5 nitric acid treatments to remove the palladium.

My last DMG test on the 5th nitric treatment showed little if any palladium.

Where did it come from? Just goes to show how difficult (for a novice like me) that PGM refining can be.

This did not turn out like I thought it would, but I gained much experience and knowlege.

I look back and see that the palladium refining was the most fun - it yielded some clean salt and pure metal.

Thanks for looking - no wonder not many people are eager to try platinum.

I have more material to work with - more to follow.

kadriver


----------



## kadriver

Lou said:


> FYI, the dilute "lazersteve" method of separating Pt from Rh and Ir works remarkably well. I call it the lazersteve method because I saw Steve employ it on some iridium containing med material and then saw the resultant platinum product. If time is not an issue, it is the pre-eminent way.
> 
> Low and slow!



I searched the forum for hours and still could not find this post.

I even searched only Steve's posts.

Can someone point me in the right direction.

kadriver


----------



## lazersteve

Lou is referring to a visit he made to a job site where I dissolved a small batch of mixed platinum alloys from medical scrap.

I have not made these methods public because they are a source of income for my family that is vital to my livelihood. The last thing I want to see is another one of my methods being publicly cloned and spawned all over the internet. If this method where to be made public it could adversely affect my income and hence my family's welfare. 

For this reason, I won't post about it on a public forum. I hope you can understand where I am coming from on this one.

Steve


----------



## kadriver

Absolutely Steve, no problem. I can clearly see how these processes are very valuable.

I don't blame anyone who does not want to reveal their hard-won techniques on a public forum.

I salute you for all that you have already given.

Aa far as I am concerned this will conclude this post - I got a great education and provided a path for others to follow.

Thank you!

kadriver


----------



## lazersteve

Kevin,

PM me if you have any further questions, I'm happy to help with what I can.

Steve


----------



## RaoOvious

Kevin really enjoyed ur fabulous series.Just concentrate on the main processes and u wod have ur answer,the secret lies in careful examination of things,which u already have done.

I would also stress that Lou should have guided u properly because his process has proved to b unfruitful,cause the whole chemistry changes when u have pt.pd.rh as blacks,and both nitric and sulfuric washes dissolve pt black as well.Just like silver alloyed with platinum and nitric wod dissolve both of them practically,same is the case with pgm blacks,one follows the other though its not supposed to follow theoretically.

Kevin great job,I would love to see another series by you.


----------



## Lou

Sulfuric washes do not dissolve appreciable platinum metal at all at any concentration ever.

NItric may dissolve platinum black, particularly if chlorinated tap water is used to dilute the solution.

Rhodium black won't appreciably dissolve in room temperature sulfuric or aqua regia. Given great heat, it will dissolve in both. 

Probably enough to say that the processes aren't quantitative (they really never are in PGM chemistry) and can be done a hell of a lot faster. In some instances, it is beneficial to do it much faster so that less other metals get involved.


----------



## Oz

RaoOvious said:


> I would also stress that Lou should have guided u properly because his process has proved to b unfruitful,cause the whole chemistry changes when u have pt.pd.rh as blacks,and both nitric and sulfuric washes dissolve pt black as well.Just like silver alloyed with platinum and nitric wod dissolve both of them practically,same is the case with pgm blacks,one follows the other though its not supposed to follow theoretically


By all means I would love to hear you expand upon "your" knowledge of this separation and share what you know. I would enjoy hearing how you would have done this differently. Perhaps you could help Lou and I both in getting clean .999 seperations of mixed PGMs.


----------



## RaoOvious

"By all means I would love to hear you expand upon "your" knowledge of this separation and share what you know. I would enjoy hearing how you would have done this differently. Perhaps you could help Lou and I both in getting clean .999 seperations of mixed PGMs".

Oz

Sorry i cant share that valuable info on this public forum.


----------



## samuel-a

Now... isn't that convenient...

You knew you would be challenged, then why say anything at all?
If you are expecting others to show thier cards, be ready to show yours.


----------



## RaoOvious

I think there has been lots of meddling regarding this matter(I cited the observation rightfully and not to have a tug regarding showing cards ) which has been settled privately with the concerned person,and he has recognized the fact that all regarding PGM chemistry can be unfruitful and unpredictable sometimes as happened with the current scenario.

"Now... isn't that convenient...", And by the way i didn,t started a thread about something unpredictable at the first place so no need to show mine,if i wod have to i wod share wid him personally.

Its not about being bully or something,it was an honest(may be got infuriated) input at something that was going no where. Hope everyone would get it.


----------



## Noxx

Quick question concerning the mixed black PGMs powder.

What are you guys doing with it ? I have some that I wish to sell.

Is it better to have it assayed first ?


Thank you


----------



## Lou

Most of the stuff that comes in like that is a zinc cement product that is high in nickel, cobalt, copper, and other base metals.


It's always better to have it assayed first. The trick will be to find someone to give you credit on the Rh. Most refiners don't consider it a payable item unless in quantity (because they themselves don't get paid on it unless there's several ounces in what they send out to JM/Heraeus). 

What is it from and how much of it is there?


----------



## kadriver

Lou said:


> Most of the stuff that comes in like that is a zinc cement product that is high in nickel, cobalt, copper, and other base metals.



Lou, is this true with mixed black derived from automotive catalytic converters leached with HCl/Cl, then the leach cemented with zinc?


----------



## Lou

I was mostly referring to the zinc cement product from spent AR solutions from karat refineries. Sometimes Pd and Pt jewelry (or dental) inadvertently get melted with the gold scrap and dissolved. After companies like ARA (or insert other karat refiner, there's dozens) precipitate the gold they are left with a raff that has PGM content. Also a similar feed from plating operations. 

I don't know about auto converters because there is a lot of range. 99.9% of people handling them get them smelted because aqueous processing isn't appropriate at 1000 ppm Pt.


From what I have seen of converters, it's usually iron.


----------



## Noxx

Lou said:


> I don't know about auto converters because there is a lot of range. 99.9% of people handling them get them smelted because aqueous processing isn't appropriate at 1000 ppm Pt.



It is true; even a very large cats buyer around here (PMR) does not refine the material. They simply assay then send their lots to a large mining company who probably has an arc furnace...


----------



## Lou

Probably Vale.

Yes. Not many processing PGMs.

Even doing a couple hundred ounce lot is small in the scheme of things...hence I consider my operation boutique.


----------



## Noxx

So I'm better off collecting the mixed PGMs black powder then separate it to their respective salts.


----------



## kadriver

I'll be doing the process outlined in this thread to refine the palladium recovered from my silver cell slimes.

I need to review carefully before I shoot the video because its been a long time since I've done it.

Part one of the video is uploading and I'll post it later today (be sure and watch because I have a delayed, runaway reacion, boil-over mishap in part one of this video for all to learn from).

kadriver


----------



## goldenpuncture

nice doscussion! i want clearify my informations even i get this info from forum. when black pgms dropped by zinc, when dissolve in AR then there will be a yellowish brown powder left behind, pt and pd dissolved in AR and this yellowish brown powder is RH. ( RH(I)) ... if so then how to refine it! ?


----------



## nickvc

goldenpuncture said:


> nice doscussion! i want clearify my informations even i get this info from forum. when black pgms dropped by zinc, when dissolve in AR then there will be a yellowish brown powder left behind, pt and pd dissolved in AR and this yellowish brown powder is RH. ( RH(I)) ... if so then how to refine it! ?




Unless you have large amounts and even more importantly the correct lab set up I would avoid PGM refining it’s dangers outweigh its value in my opinion.


----------



## goldenpuncture

may be not a proper set up but its pretty safe and at least very safe according to my area. yes i hav'nt large amount as i practice last month with only 2 kg honeycomb. now i am working on 30 kg, collecting black zinc percipitated . so i can reprocess large amount at once. got some fumes in start and as i was succeeded then i arrange gas masks, make a fume hood, buy new gloves. though its still not pretty safe but its batter to work with pgms, sorry can not make fotos but i want learn to test this yellowish brown powder for rhodium. with stannous chloride! need help


----------



## Platdigger

Well first, to do any testing with stanus you will need to put that powder into solution.
Try small amounts to see if an acid will dissolve it.
May take hot sulfuric. If not, you can always do a fusion.


----------



## Raza shahid

Hello gyz i am new here i think i need some help. I am doing with mlcc and i precipitated black pgm powder from Al, but when i tried to dissolved. Black pgm powder in aqua regia it did not disolve. The solution is greensh yellow in color with black powder in it..


----------



## FrugalRefiner

Raza shahid said:


> I am doing with mlcc


What do you mean by "doing with mlcc"? I understand you're doing _something_ with mlccs, but what? are you smelting, using nitric acid, hydrochloric acid, something else? Are you crushing them, leaching them whole, hot acid, cold acid, stirring,...



> and i precipitated black pgm powder from Al,


Aluminum is one of the most reactive metals, and will cement everything below it on the reactivity series, not just pgms.

Please provide some more details on how you got to this point.

Dave


----------



## Raza shahid

I am tryng to recover n refine pd salt from mlcc. Firstly surface elemination with hcl then sponge the liquid n treat the solid with aquaregia 32% hcl n nitric acid 1:3 then add Al in solution n soon i see black ppt of pgm now i have to disolve the black ppt in acid. so if u can help me. I appreciate it


----------



## ashir

your phenomena is totally wrong. you can not use aqua reigia on mlccs. as you will loose silver and might be dump the whole acid with base metals. you can not get any value from mlccs without crushing them. be calm, study more, try to post pictures...! if you are from pakistan then pm me!


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## ashir

ok guyz. here what happenings to me.leach honeycombs with hcl/cl mathod. drop the black pgms with zinc. wash well and dry pgms. use nitric to remove pd. drop pd with DMG. 
then the remaining black powder was dissolved in hcl/hydrogen peroxide. still can not dissolve all black powder but got a redish yellow solution with 2 treatment with AP. evaporate it and use concentrated ammonium chloride solution. but nothing comes out. i use zinc to reget the black pgms from AP solution but it gives brown rusty type particals. 

now i try to process the remaining black powder from AP mathod that was not dissolve. i use hcl/hydrogen peoxide. no heat. after all night it still not dissolve in AP. try to heat it but nothing happens. 
any sugges? any help,?


----------



## Platdigger

So, how much pd were you able to separate from these powders with nitric? Were these pre cats?


----------



## ashir

not assure about quantity, as pd salt is not pure and i have troubles to get ammonium hydroxide. so i have to wait till i get nh4oh. and about cats, these are mix, petrole vhicles in pakistan( mostly made by japan) and china made cats. should i try to dissolve remaining black pgm with concentrated h2so4 ? and one more try to zinc percipated gryish powder with AP? thanks for response!


----------



## Platdigger

You could try the sulfuric, but also you could do a bisulfate fusion on a sample of these powders.
Also I would think the cats from Japan will be much better than the ones from China.


----------



## ashir

thanks platdigger!!! here what i did next, add hcl to brownish powder and got a fine black powder... sorry wind was angry last night 
and the sulfuric treatment to insolubleblack poder. 
it was concentrated h2so4. color show there was no rhodium and if it was then very little. now i will test rh with stanous chloride. any further suggessions! ????


----------



## Platdigger

PM sent


----------



## ashir

i am posting about a problem with black pgm. now i clear it more so someone can help me out! i got black pgm leached with hcl/cl and use zinc to get pgms. treated with nitric for pd. later i use hcl/peroxide to dissolve pt. now i have some powder not dissolving any more in hcl/peroxide, even nothing happen in h2so4! what i should do next? 
look its color which is not completely black. its bluesh type . any help please


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## Platdigger

What is the source of your zinc?


----------



## ashir

its spareparts of bikes and vhicles! melt them and get the melted zinc! in long pieces!


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## ashir

thanks platdigge! i got one more mistake, i try on whole bunch , not a sample of remaining unknown powder! well here is the pic of zinc that i use


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## jimdoc

Zinc from "spareparts of bikes and vehicles" can be unknown alloys that add impurities.


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## ashir

ok . i already guess as i read kadrive post about cab-o-sil in zinc. but i am still assure i do not get 40 gram impurities in 60 gram powder! is there any way to find out if it is impure zinc substances or something else?


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## ashir

is ther any way to find pure zinc? here in pakistan ,zinc sheets are not available, as a zinc source i also use toys,door handels, some mobile bodies, dry cell covers, but main source is vhicle parts and here is a pic of impurities i seprate by melting zinc


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## Lino1406

Use aluminum sheets (if you don't have too much nitric). You may need to brush them from time to time. Also raise pH = 3


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## ashir

thanks for reply! is aluminium fine to percipitate pgms? as i read on this forum that pgm black with aluminium can cause trouble. i will try to find thread, and also i not use nitric. i use hcl/cl leach mathod, ?


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## ashir

Lou
Active Member
PostNovember 6th, 2008, 7:37 pm

I'll give you the short answer: 

In this case, Hoke is wrong. Aluminum is inconvenient to use because it is tough contaminant to remove because it forms sticky gels (like what tin does with conc. nitric, metastannic acid goo!). 

To understand why it is such a royal pain, you must know something of its aqueous chemistry. 

When you go to do a cementation reaction, you are basically using a reactive metal to displace a less reactive metal. That much you know. When the aluminum or zinc goes into an acidic solution, it produces hydrogen gas. It is both the nascent (new-born) hydrogen that does the actual reduction of these metals and the chemical potential caused by the flow of electrons. Gross simplification here. 

The problem with aluminum is that it has problematic aqueous chemistry and can do several things. When you put aluminum metal into this hydrochloric acid solution, you get "aluminum chloride hexahydrate" (not really, actually it is a mixture of many things: [Al(H2O)6]3+ + H2O --><-- [Al(OH)(H2O)5]2+ + H3O+, and also the benign complex AlCl4-). In short, this is hydrolysis. This is driven by the low Ksp of hydrous aluminum oxide, Al(OH)3. Now you may ask, why am I getting a seemingly basic precipitate (note the OH function in it) when I am doing a reduction at low pH in hydrochloric acid? Well, alumina is called an acidic oxide for this reason, it precipitates at low pH! Recall that water autoionizes into both hydronium (H3O+) and hydroxyl (OH-) ions. This is because water is amphoteric and acts as both an acid and a base. Well, as luck would have it, so do many other things, in particular aluminum hydroxide. The hydroxyls from water's autoionization will hook up with any AlCl4- and any hexaaqualuminum (III) floating about (which is what happens when aluminum cation is present with excess water from HCl). 

So what does this mean in practical talk? It means that even at low pH of around 1 (which is equivalent to 1M HCl) you will have some aluminum hydroxide beginning to drop out because of hydrolysis. I think the actual math (which gets nasty if solved exactly, 8 or 9 unknowns) says it starts at pH 1.4. Anyhow, this gets entrained and mixed up with your cemented values and becomes hell to remove. It requires a boil in base (to complex the aluminum hydroxide as soluble aluminate, Al(OH)4-) or in a very conc. solution of HCl. Aluminum hydroxide forms alumina upon heating, a very stable entity--it is used as refractory for lining steel ladles or as an abrasive, or in sapphires in rings. 

Did I also mention that this aluminum hydroxide is very flocculent and slimy and will clog filters? It is a pain to remove from your metals. Pure Al(OH)3 made by an analytical chemist with good technique and know how won't do this, but I can guarantee you, it will when you try it. Not trying to insult, but there is a lot of math, technique, and art to it. It ties in with selective precipitation techniques, also a good tool for refining! I'd be willing to discuss this all in more detail with math and examples if there is enough interest...


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## ashir

last time seperating pgms from black powder stuck. got 10 gram palladium by nitric/dmg . later alot back yellowish powder was hard to dissolve in any acid/ AR, at any temp! so i got more 200 gram black pgm. i want saperate pgms by bisulfite fusion. can any one guide this process or any link?


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## Raza shahid

Hi kad river you done great job my friend, u r active member here, my friend i need some help of yours to get pdcl2 brown powder or brown salt i have refined pd salt from mlcc and at the end of chlorination process i got some yellow salt may be ammoniumhexachloropalladate, but i need pdcl2 can u please help to achieve this i think calcing process can evolve ammonium chloride to get pure pdcl2. But i may be wrong i need to know the right way, it will be appreciated.


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## FrugalRefiner

Raza shahid, please do not use text lingo like "u r" here. Many members have to use translators, and things like that do not translate well.

Dave


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