Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Extracting PdCl2 from a carpet
As you can probably guess from the title, I fucked up. Fortunately the carpet that now has several hundred dollars with of palladium in it was one I
picked up on the curb, and it was getting a bit gross a year later anyway. If I can extract the palladium from it, I'll have more than enough funds
to get a much nicer replacement off Craigslist.
I aired out the acid smell, and figured I'd dissolve the PdCl2 out with water with HCl or a chloride salt dissolved in it. However, I've noticed that
a lot of the orange stains are starting to turn black, indicating a slow reduction to palladium metal, which will obviously not dissolve in an aqueous
solution of chloride ions. Now, I'm quite aware that aqua regia dissolves palladium, but I'm concerned that it might be better at dissolving carpet,
and I can't afford that much nitric acid to make the extraction worthwhile.
However, I am familiar with the use of sodium cyanide in industry to leach gold from ore, and preliminary tests have confirmed that the black
palladium stains CAN be removed slowly by a very dilute KCN solution. I've used cyanide solutions for electroplating gold and silver, but I've never
heard of anything similar being done with palladium, probably because it plates well from safer solutions. Obviously I don't want to go fucking
around with cyanide before consulting seasoned industry experts. But I don't know any, so I figured I'd post here instead.
So I guess I'd need to do two separate extractions. One, using a chloride salt to dissolve out the PdCl2 that hasn't been reduced yet. I was
planning to use MgCl2, since I needed some once, and bought a ten-pound container of it (much more than I needed) when I saw it on clearance as an ice
melter. I haven't come across any information indicating that this salt wouldn't work, but there aren't exactly a lot of papers published on this
particular type of thing. I should probably just use NaCl to be safe though; its salts' solubilities are a lot more predictable. Anyway, I'd do
however many extractions this way as I needed to until the solution was clear when left overnight. Then I'd filter it and probably crash out the
oxide/hydroxide with H2O2. Possibly some sodium thiosulfate as a chlorine scavenger, but I don't think either the hydroxide or oxide of palladium
would react particularly strongly with chlorine, and since the solution would be acidic, I can probably just let it sit until there was no chlorine
smell, if there was ever any in the first place. My main concern is the nitrate ions that will be in solution, which can cause significant palladium
to go into solution in that much water at that pH. My normal thought would be to boil off the water and heat to decompose any nitrates, which would
make the rest of the extraction easier, but it might be easier to just add a bunch of NaCO3 to the solution to raise the pH enough to crash all the
palladium out. I think this would work, based on what I've read, but I'd feel more comfortable just boiling the solution down as soon as possible so
there's less volume of it, and I can use normal glassware on it.
I'd probably have to neutralize pH, add a metal powder to selectively precipitate palladium, then dissolve away that metal using an acid that doesn't
dissolve palladium at some point. I know zinc is frequently used, but that's typically done once it's been established that the solution only
contains noble metals, which is obviously not the case for my carpet. There are many acid and metal combinations to choose from though, and I can
probably get away with a simpler extraction than the ones I've read so far, since I'm pretty sure palladium is the only precious metal that's in my
carpet in significant amounts.
The second extraction would be with a dilute solution of potassium cyanide, soaked overnight outside. There's no more than 10g of Pd in the carpet,
and only a fraction of that has been reduced to metal, so I wouldn't need much. Filter, then neutralize the cyanide with H2O2. Titrate to a neutral
pH, then add zinc powder to plate out any Pd that is still in solution. Filter, rinse with distilled water, then dissolve the zinc away with some
acid that won't dissolve Pd (there are plenty, and I can use whatever I happen to have on hand). Rinse, filter, then combine both extractions. Rinse
again with dilute H2O2 (does Pd form fulminates? this would decompose them if it did, right?), then distilled water. Heat the precipitates, adding
heat slowly until it's glowing. Now it should be possible to dissolve in HCl and/or aqua regia to get PdCl2.
There are a few things I don't know, one of them being if I should be that concerned about other metals and/or metal salts that would somehow make it
through these extractions and contaminate my palladium. Silver is a possibility, since I've done silver plating in that room, but there would hardly
be any, and that would easily precipitate from a chloride solution. Iron would form ferrocyanide complexes, but I doubt any would survive the first
extraction, which would be somewhat acidic. I'm also unsure at what point I should apply some method to the first extraction to either selectively
precipitate palladium or remove base metal salts. I'm not super concerned with purity, and 1% impurity is acceptable for most of my purposes. I
still have plenty of the purer salt for any applications where purity is important.
There's a lot to take into consideration here, and assuming I can actually complete all these steps without more accidental spills, would these steps
actually work? Some of these things I've actually done before, some I've read about and verified that they work, and there's probably a reaction or
two in there that I've done before but am remembering the details incorrectly.
Anyone feel like helping a clumsy chemist learn from his last mistake and not make more?
[Edited on 8/31/16 by Melgar]
|
|
|
Lefaucheux10
Harmless
Posts: 30
Registered: 28-8-2016
Member Is Offline
Mood: No Mood
|
|
bad day in the lab :/
this made me think about an old story of Martin Poliakof about Plutonium 15min 10 :
https://www.youtube.com/watch?v=89UNPdNtOoE
so for me the carpet will act as a sponge and il will be complicated du work with since a lot of solution will not come out easily
the better solution for me is to cut the carpet and to burn it in a container
the ashes must be contain palladium or palladium oxyde in a concentration much more consequent than in litter of water needed to wash the carpet
the ashes are in majorité alkaline species in case of a natural material carpet likes carbonates or hydroxydes
for me it's more convenient and you will need less chemicals to process the ashes thant te carpet
( scuse my poor french men english )
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Quote: Originally posted by Lefaucheux10  | | so for me the carpet will act as a sponge and il will be complicated du work with since a lot of solution will not come out easily
|
Correct, that is why I plan to do several rinses and soaks. I also only plan to cut out the 8-10 square feet of carpet that could have gotten
splashed, and only extract from that part. Conveniently, PdCl2 is a yellow, orange, or dark brown color when in solution, depending on concentration.
Since it colors solutions so well, it would be especially easy to detect when the pieces of carpet stop coloring the solution after a long soak.
PdCl2 is apparently soluble in organic solvents, so I could dissolve anything remaining with whatever easily-evaporated organic solvent is cheapest.
That's actually one of the few things I would trust denatured alcohol to do, since it has so many chemicals in it that one or more of them are bound
to dissolve Pd well. E85 might be a better choice if I want to save ten bucks or so. I guess I still need to know if there's anything special I'd
need to do to the hydroxides and oxides to extract them, or if those would be dissolved by KCN solution. I'm pretty sure they would be, at least at
low KCN concentrations, which apparently are what you need for precious metal leaching with cyanide.
I can't really burn it, because I'm living in Manhattan... outdoor polyester fires are frowned on. Not to mention, polyester smoke is really thick
and black. It'd be impossible to tell if any of the soot being carried away was actually palladium. The only way to reasonably do it would be to
burn in small pieces, piece by piece, with pure oxygen, but that'd be expensive. Maybe I could borrow an oxygen concentrator, but I think I'm still
going to go for the salt extraction followed by cyanide extraction, since if I fucked up burning polyester with that much aqua regia soaked into it,
there WOULD be plenty of dioxins formed, and I don't have the equipment to mitigate a risk like that.
Now I'm wondering if I shouldn't just do all the PdCl2 extraction with E85? Probably not, because I haven't actually used it as a solvent before, and
would prefer to risk a smaller amount of palladium. I also don't know how strongly it smells, to evaporate that much of it.
[Edited on 8/31/16 by Melgar]
|
|
|
clearly_not_atara
International Hazard
Posts: 2696
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Apparently PdCl4(2-) forms soluble complexes with glycine:
http://pubs.acs.org/doi/abs/10.1021/es00077a014?journalCode=...
This is probably a much safer choice than cyanide...
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Cyanide is, as far as I know, the most effective reagent for leaching small quantities of finely-divided noble metal, not salt, from a porous
material containing it. I have plenty of experience using cyanide for dissolving gold and silver for electroplating, don't worry.
|
|
|
Dan Vizine
National Hazard
Posts: 628
Registered: 4-4-2014
Location: Tonawanda, New York
Member Is Offline
Mood: High Resistance
|
|
I think that Lefaucheux10 has the best idea, but 10 square feet!? That's a lot. However, the liquid reagents needed to do an efficient extraction will
also be huge, and still leave any reduced metal behind. And, without a rotary evaporator, a huge task to process.
I doubt if significant Pd would leave in the smoke. I'd do a number of ignitions of smaller pieces at night. Maybe in whatever local spot is not
teeming with people?
A number of decantations of the burnt slurry in water should allow you to separate much of the burnt organics. Then a total ashing of the remainder,
more decantations.
Finally, treat residue with aqua regia. Concenrtate to drive off most of the HCl and all of the HNO3. Dilute. Treat with aq. NH3, followed by HCL to
precipitate Pd (NH3)2Cl2. Re-dissolve in excess NH3 soln, ppt. with HCl, ignite to give Pd sponge.
You won't get pure Pd without excessive work. Oxyacetylene with an oxidizing flame will melt it. Or just sell the Pd sponge to a refiner
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
Deserve"...F. Zappa
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
| Quote: Originally posted by Dan Vizine | I think that Lefaucheux10 has the best idea, but 10 square feet!? That's a lot. However, the liquid reagents needed to do an efficient extraction will
also be huge, and still leave any reduced metal behind. And, without a rotary evaporator, a huge task to process.
I doubt if significant Pd would leave in the smoke. I'd do a number of ignitions of smaller pieces at night. Maybe in whatever local spot is not
teeming with people?
A number of decantations of the burnt slurry in water should allow you to separate much of the burnt organics. Then a total ashing of the remainder,
more decantations.
Finally, treat residue with aqua regia. Concenrtate to drive off most of the HCl and all of the HNO3. Dilute. Treat with aq. NH3, followed by HCL to
precipitate Pd (NH3)2Cl2. Re-dissolve in excess NH3 soln, ppt. with HCl, ignite to give Pd sponge.
You won't get pure Pd without excessive work. Oxyacetylene with an oxidizing flame will melt it. Or just sell the Pd sponge to a refiner
|
PdCl2 is my end goal anyway, so I'd probably stop there. And I guess after thinking about it, I should probably focus on the 2-3 square feet that got
most of it. It's been really frustrating since then, since any time a dangling plug gets left near that spot, it's all rusty the next day. It smells
like vinegar now, more than anything. I don't use acetate salts all that much, so I'm wondering if the Pd is catalyzing the oxidation of my carpet
into volatile organics, and perhaps acetic acid is just the strongest-smelling one?
Burning it might be the way to go. Although I live in Manhattan, my friend said I could do whatever I needed to in that respect at his dad's garage
in Brooklyn. There HAS to be some sort of apparatus that can fully burn a sample in order to extract the ash, using propane and an oxidizing flame.
I'm sure it'd be out of my price range, but maybe I could build one.
|
|
|
unionised
International Hazard
Posts: 5104
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
Since air is free, burning the carpet will be the cheapest way to simplify the problem to one of manageable proportions.
A smouldering fire, while stinky, will have the least losses by vapourisation.
If you add something like Na2CO3 bafore you burn it the Pd will be largely reduced to the metal in a smokey fire and so will be insoluble in
non-oxidising acids.
So you can leach the ashes with something like vinegar to remove most metals.
Then you can extract the ashes with an oxidising acid to get the Pd.
The problem is that the carpet will have sand in it so you may get some glass formation.
|
|
|
Melgar
Anti-Spam Agent
Posts: 2004
Registered: 23-2-2010
Location: Connecticut
Member Is Offline
Mood: Estrified
|
|
Dissolve any additional solids in molten NaOH? Then dissolve in water, decant and attempt to dissolve residue again?
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
Here's a modification of what we do when we process carpets for jewelers minus all the knitty gritty.
1. Pyrolyze carpet.
2. Incinerate ash residues/
3. Ball mill ashes with x lbs copper shot, y lbs pounds borax glass
4. Heat to 1200 C and hold for several hours, pour a cone of metal and separate the slag.
5. Remelt into an anode. You can drill the anode, dissolve in nitric, dilute to 1 M and use alcoholic dimethylglyoxime to determine Pd.
6. Plate out copper in copper sulfate/sulfuric acid; 150 g/L sulfuric acid, 125 g/L CuSO4, few g/L gelatin, SS316 cathode smaller than the anode.
7. Dissolve the slimes HCl/H2O2.
8. Boil to expel chlorine.
9. Cement with copper foil to get only the Pd--or else heat with sulfuric acid until all the HCl is distilled off and proceed to the precipitation in
10.
10. Collect Pd black. Dissolve in H2SO4, precipitate as PdBr2, with stoichiometric NaBr, filter and rinse with cold DI. Slurry in HCl, and boil and
add peroxide drop wise until bromine is gone and palladous acid remains. Evaporate to a syrup until PdCl2 deposits.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
