refining 79% palladium bal silver alloy

[pyromaniacguy]

Hello all,

I have roughly 50 troy ounces of palladium membrane material from a large (plant sized) damaged gas purification system. I called around and the best offer I got on the material was not even 200$/oz - that seemed a bit low given the fact that at todays spot the palladium content is worth close to 50% more than that figure.

Ive done a little research online and cant seem to come up with an easy solution to refining the material myself that doesn't require digestion in nitric then selective percipitation (maybe thats why the price I was offered was so low!), based upon commercial refining of crude ore for PGMs

I would LOVE to find a simple process like quartering used to refine karat gold. If such a process is possible the material has a HUGE surface to weight ratio, it's made up of thin tubing with a wall thickness of maybe .001 or .002" so if I don't have to further dilute the palladium to avoid masking that would be great...

any suggestions would be greatly appreciated!

FWIW I'm an optics jock by trade with an education in physics. My last chem course was quite a long time ago. I may remember the difference between chlorate and perchlorate, but go easy on me please!

 

[orenda1168]

While I don't know who you spoke with about palladium-silver separation, I suspect, based on my activity a number of years ago with the forerunner to Johnson Mathey (Bishop Platinum) in their precious metals refining lab, that the ~$200/ounce quote qiven was within reason. The separation process and purity refining is sufficiently involved that I doubt you will want to pursue it yourself, particularly for the quantity (and value) involved.

Orenda

 

[pyromaniacguy]

Orenda1168,
What is the process?

When I sell fine scrap to my local precious metals dealer, I normally get 95% back from spot. They are closed for the holidays so I don't know if this figure will apply to palladium but I have sold both gold and platinum to them at this price many times before in the past.

I run a small business so everything comes out of my back pocket at the end of the day. depending on refining losses we are talking about as much as 6 or $7000 between selling as is and refining myself. Thats a fair bit of incentive to break out the ole chemistry set in my book!

Thanks and happy holidays!

 

[orenda1168]

Pyromaniaguy:

The attached will give you a birds-eye view of palladium separation and purification, particularly the last two paragraphs.


Refining of
Palladium Bearing
Ore
The refining process is indeed the most complex
and time-intensive aspect of PGM recovery. As
a result, mining companies continue to devote a
considerable amount of their capital resources
to developing new, and presumably better PGM
refining technologies. While the major mining
companies go to great lengths to protect their
proprietary refining methods, the basic parts of
the process remain fairly consistent throughout
the industry.
The obvious goal of the refining process is to
further separate minerals containing platinum
group metals from base metals and other
impurities to obtain the highest-grade PGM filter
cake possible. Though the process becomes
incredibly detailed, it can be condensed into
three main activities: pressure leaching, solvent
extraction, and PGM precipitation.
However, the refining process does not adhere
to a strict linear progression in the way that
some of the preceding steps do. Rather, it
involves a set of discrete circuits designed to
isolate different metals.
The concentration and smelting of PGM-rich ore
produces a successively higher-grade filter-cake
that lends itself to the series of intricate
chemical processes carried out during the
refining phase.
The enriched converter matte received from the
smelter is subjected to a batch grinding process
in a closed ball mill, producing a heated slurry,
that is then cooled and stored in a surge tank
before it is conveyed to a series of autoclave
leach circuits, each designed to precipitate a
particular metal from the solution through
pressure oxidation.
Pressure oxidation, the process of conducting
chemical reactions under high pressure and
temperature, can take a variety of forms. Most
mining companies, however, rely on the high
solubility of PGMs like palladium and platinum
(as well as gold) in aqua regia, a mixture of
hydrochloric and nitric acids.

Aqua regia leaching dissolves platinum,
palladium, and gold minerals and leaves other
PGM and base metal components as solids in
the leach residue. After the gold is segregated
from the solution through a process called
solvent extraction, the remaining solution is
treated with ammonium chloride to precipitate
the platinum as ammonium chloroplatinate. The
crude platinum salt that results is then heated
to create a fine platinum powder. It is then redissolved
in this form in aqua regia, precipitated
once more with ammonium chloride, and
calcined to pure metal.

The palladium, still left in solution, is
precipitated with ammonia. The crude palladium
salt produced by the addition of ammonia is
recovered through filtration, re-dissolved in
ammonia, and precipitated to form high-grade
palladium salt. This powder is usually converted
to metallic form through chemical reduction
involving formic acid.

Good luck!





Orenda

 

[pyromaniacguy]

Orenda,

Thanks for the information.

However I must ask if I'm missing something here. Would the silver also not percipitate out from aqua regia with the addition of ammonia? If not and a simple reduction to metal is all I have to do it sounds like it's worth the 6 or 7,000 dollars to me!

Any idea as to the recovery rate with this sort of process?

TIA!

 

[orenda1168]

Pyromaniaguy:

The silver should precipitate out as silver chloride during the aqua regia step, then removed by sedimentation/filtration, leaving a relatively pure palladium solution which would then be treated with ammonia for palladium precipitation.

I don't know the specific recovery rate of palladium in this process, but would hazard a guess of something in the 99% range or better.

If you pursue this, be very careful with handling aqua regia and ammonia......they both are hazardous! You still will probably be better off selling to your scrap dealer at the 95% of spot he has paid you in the past.

Orenda

 

[pyromaniacguy]

Orenda,

My scrap dealer only buys fine scrap at 95% spot - for sales to local jewelry stores and what not for karating and other such in house needs. if I sell the metal as is I'll only get about 60% spot. They can send PMG bearing alloys out for refining just as I can but they dont get any better rates for palladium bearing scrap than I do it seems. Given the signifigant disparity in the value offered for the scrap and current spot I had assumed that it would be a difficult undertaking to refine the material myself, but it doesnt sound very difficult. I'll try a small batch as see how it goes when I have time.

In the mean time if anyone would care to suggest any other, better routes, please by all means do so!

TIA!

 

[orenda1168]

The difficulty in palladium processing isn't the chemistry, it's the equipment and chemical knowhow to to the job. Having been there and done that, believe me when I say that, given the apparent fact that you are, 1) not a chemist, chemical engineer or otherwise a chemically trained individual, and 2) probably don't have either the required reagents or containers to effectively do the job, this is a matter that is better left to those in the business. Greed is not always an approach that leads to monetary gain!


Orenda

 

[pyromaniacguy]

Orenda,
I have plenty of glassware and a fume hood to work in. I have nitric and hydrochloric on the shelf and can order whatever I need from my local chemcial supply house. I run a small business so I have access to the proper tools, I wont be doing this in my garage.

Yes I'm not a chemist, and I'm not only motivated by greed. It sounds like a fun project too!

 

[orenda1168]

Pyromaniaguy:

Well, good luck to you! Let us (me) know how you make out with this.

Regards,


Orenda

 

[moltenmetal]

Wow, I'd say there are easier ways to make $7k, don't you think? What guarantee do you have that the purified material you make is going to be pure enough to warrant double the price? But I guess if you want to take it on as a dangerous "hobby", it's worth a shot.

 

[pyromaniacguy]

moltenmetal,

it's 4 nines palladium right now - mixed with 4 nines silver... it will be pure provided i can just separate the two....

after doing a bit more research online it looks as though electrorefining may be the way to go. It seems that by using controlled potential plating it has been reported in the literature that one can remove concentrations as low as 100 ppm silver from palladium with no codeposition of the palladium after two cycles.

This seems as though it would be preferable to me as i dont have to worry about reducing anything to the metal. I still need to have a look at the original paper, I only found it cited as a reference in a book.

Chemistry is fun. what easier way to make 7k$ is there than doing something fun?

 

[moltenmetal]

If you could magically make the metals move apart from one another without adding anything to help, then your pure palladium and pure silver would be guaranteed to remain pure. Make sure that whatever reagents you use are not contaminated with trace amounts of stuff that the end purchaser can't tolerate, or your hobby may cost you more than just the (significant) risk of playing with aqua regia, and it may gain you nothing other than disposal costs for your efforts.

Hey, people do wierd stuff for fun, so why shouldn't you take this on? I do sand castings for fun, and it doesn't make me any money. Doesn't cost me anything either, though.