Mixed Black PGM Powders

[samuel-a]

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.

 

[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.

 

[kadriver]

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.

(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.

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.

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]

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]

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]

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.

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]

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