# 2% Palladium on Carbon



## kjt124 (Aug 5, 2012)

Hi guys! I am new here and reading rapidly - thank you all for the WEALTH of information here!!

Thus far I am not seeing a thread that deals with what I am working with directly, but I apologize if I simply haven't found it yet. I recently came across what I believe to be a wonderful find - about 20 kg of 2% palladium on carbon catalyst in virgin form. What I am doing so far is cooking the powder in cast iron on a propane flame until it gets to the point that the carbon will support its own combustion (mild agitation to keep it going).

I was expecting (after polish burning the mixture) under ideal circumstances that I would get the final mass of the mixture down to the point where I should expect the concentration of Palladium to be around 85% or so (being that I am obviously turning it into PDO)... However, the best I can seem to do with this step is about 40%.

Clearly this is not carbon in which the Palladium is trapped - it is charcoal and now I have PDO in ash...

So far I have a completely dry and harmless process (other than heat). However, I am a degreed chemical engineer and very much understand the ins and outs of working with chemicals if I must... Not to mention I plan on trying my hand after I get a bit smarter with the scrap Gold refining and that will clearly have me looking in the chemical catalogues.

Does anyone have a suggestion for the most reasonable way to get this palladium out of the ash? Right now I am certainly on a budget as I am hoping this Palladium will serve to fund the expansion of my operation. However, luckily I have the luxury of time. I know this stage of the process of debulking the mixture will easily take me 2 months or more balancing it around work, etc.

I appreciate any advice anyone can give and again - if there is already a thread for this sort of thing, I apologize for the duplication.

Thanks!!


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## lazersteve (Aug 5, 2012)

PdO is slightly soluble in in AR, aside from that you may try a gas phase extraction if you are set up with a tube furnace.

Carbon will complicate any filtration process due to it high surface area and liquid retention.

I would heat a small sample in AR and see how well it extracts the Pd.

Steve


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## kjt124 (Aug 5, 2012)

So far that is pretty much what I was coming up with... I suppose no direct smelting type of operation is expected to be very successful when the ash is apparently about as abundant as the Palladium, eh?


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## Lou (Aug 6, 2012)

You can melt it with copper and blow methane through it and the Pd will dissolve.


Alternatively, you can sell it to me and I'll process the material for you. 


PdO dissolves nicely in HBr. Alternatively, you might just want to reduce it all with sodium formate, filter, then do an aqua regia digest on the residues.


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## kjt124 (Aug 6, 2012)

You, sir, have given me some interesting research projects. I will certainly consider selling the material to you, but I am definitely in this for the learning as well. Much research to be done...

Thank you very much!!


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## freechemist (Aug 14, 2012)

"Virgin" Pd on carbon is usually active carbon, loaded with varyied amounts of PdO by impregnation with an aqueous acidic Pd-solution, followed by slow elevation of the solution-pH in order to deposit solid PdO on it's surface.
In my practice the best method to recover Pd was to burn down as much carbon as possible, followed by tempering the remaining "ash" at about 600oC under good aeration.
Under these conditions Pd-metal takes up oxygen to form PdO, which eventually is reduced by carbon, still present in the mixture. Heating to 800oC - 900oC leads to thermal decomposition of PdO to the metal and elemental oxygen. Thus, repeating the tempering/oxidation - thermal decomposition cycle leads, after a last decomposition step under exclusion of oxygen, to Pd-sponge containing only minute amounts of carbon.


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## kjt124 (Aug 16, 2012)

Hmm... So I am already with you on the first step of burning off the 'bulk' carbon - and this was listed as activated carbon. What I am doing is burning it off in cast iron over a propane in air flame. After about an hour or so on the heat the carbon is able to support its own combustion and as far as I have been able to gather the carbon is burning between 400 and 500 C so I don't believe I am with you just yet on step 2. Following several batches of bulk burn, I combine them for a polish burn on the low heat flame and I go until I can not make any portion of it glow - signifying to me that I have reached the limit at that heat.

I have also made myself a small refractory furnace fueled by propylene/air flame. From what I can tell I should be able to get that up to around 1200 C. Is the 600 C step a specific plateau that I want to control carefully? Or is it simply a conservative measure and steps 2 and 3 would technically be able to happen simultaneously? (I have no means of actually monitoring temps that high yet) As a side thought - would direct flame be a bad idea for this part even if I ignore the obvious "blow my powder away" part?

I have to imagine that the final step you mention under exclusion of Oxygen, resulting in Pd sponge would need to occur in an induction furnace? Or perhaps a reducing flame like Oxyhydrogen? Or is a well balanced fuel air mix on the flame in a refractory furnace sufficient to prevent inclusion of Oxygen on the Pd?


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## Lou (Aug 16, 2012)

Incineration can be lossy if done in the open, uncovered. 

You will be left with a fine Pd powder. Heating strongly to 1200 C will oxidize it but will make it sinter.

You can not torch melt palladium and have it be oxygen free. It is a very gassy metal and will be brittle if oxygen is still dissolved in it (or other gases). Less melting is better. If you want to work it, it must be melted by briquetting and putting into an induction melter and melted in vacuo.
It is bad form to use carbonaceous fuels (acetylene usually) for PGMs ostensibly due to carbidization.

Personally, I'd dissolve up the incinerated powder in HCl/H2O2 and then filter and use the excellent treatment outlined by 4metals (the most complete method on the forum). Reduce that with sodium formate, rinse, dry at low heat and trade it for bars. I for one would trade you for Pd bar.

Lou


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## kjt124 (Aug 16, 2012)

I must admit I am very concerned about carbidization as I imagine it is difficult to revert to palladium. I just incinerated a 2.8g sample: 20 min indirect flame in the furnace and then 4 min of direct fire... I definitely got something that looks like sponge, but it is dark grey enough to make me nervous.

Let me curb my excitement a hair and get a bit smarter especially with the 4metals treatment as I definitely have no induction capability yet.

Once again, I really appreciate the help and knowledge the pros on this site deal out for free. Beginner hobbyists like me eat this up like candy  One of these days I hope to give back to the community


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## Lou (Aug 17, 2012)

Good luck! Let us know how it goes.

If you want a shiny button out of it all, you can make one with O2/H2. Just remember that it'll be very contaminated with oxygen.


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## kjt124 (Jan 24, 2013)

It occurred to me that I have been drinking up knowledge on the forum, but I never went back to this thread to finish it off...

I decided refining this material was out of my league - both from an expertise and a safety point of view so I sent the material to Lou for professional refining.

In the spirit of other posts here I will not go into money or anything, however here are the conclusions from the experience:

The quality control on Palladium on Carbon catalyst (and from what Lou has alluded to, other similar catalyst mixtures) is poor at best. Overall this turned out to be more like 1.2% Pd on C.

Conversely, Lou was an absolute treat to deal with. He was professional, courteous, receptive to courtesy, and I couldn't imagine a better introduction to dealing with a professional refiner. I am probably spoiled right off the bat, haha!

This is a personal and public thank you to Lou!!


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## Dan Dement (Jan 24, 2013)

Kjt124,

Welcome and I am certainly no refining guru and you certainly are in great hands with Lou. I do have a little experience with PM metals in powder form and trying to melt them in an induction melter. I have fried two machines in five years trying to force a heavy concentrate of Pd/Pt powder to melt. In a medium freg. Ti Induction Melter, the 5 Kw of induction melting power does not do into powder but passes thru and goes back into the machine. $12,000 mistake and I was down for over 6 weeks. The second time I did it, (about 2 weeks ago) the coil sprung a water leak before the 70/30 Au/Pd mixture melted. Awaiting new coil and parts which is only $1,000 this time. 

Understand, we cast Pd almost every day but I just must warn you that Pd Powder is very, very difficult to melt. Even if you can melt it, it is going to too brittle to use in Jewelry if that is the direction you are going. Even if you get it to metal, it is still going to need to be refined. I have learned my lesson and I just send it to be refined. I need my toys and use them everyday. Good luck in your venture.

Dan


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