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Dr.Freemanstein
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Reclaiming precious metal confusion
I have been trying to find info on how to reclaim p/metals from old pc parts.
Anyone know the processes to use to extract specific metals??
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Twospoons
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Gold - Don't expect much return, theres very little gold in old pc parts. That gold plating you see on the connectors is only 25um thick.
Silver - is so cheap its not worth the effort.
Palladium - a bare trace in a few parts.
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Dr.Freemanstein
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Thank-you...how do i liberate them tho....should i want to make the effort??
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Lambda
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About ten to fifteen years ago, a South African man became miljonair on an electrochemical process in depositing all these metals at once on one
single electrode. Electronic appliances were disembled, separated, and crushed up to a powder like consistancy. This is all I can remember, for the
information was limited in depth. He most probably had applied for a patent on this process.
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Mr. Wizard
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Silver is so cheap it's not worth the effort? At over $7 a Troy Oz you can almost get an ounce out of 2 or 3 heavy duty contactors. They are
often found in the trash cans behind shops that do heavy electrical work. Almost every relay has a pair of silver buttons in it. The higher the
current, the bigger the buttons. They get a blackish tinge when they are worn.
I had a mayonnaise jar full of contacts, and melted them down to a big silver slab.
Dig deep my friends, there be treasure in them chests
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The_Davster
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Do you have any pictures of these connectors? I am not sure I know what they look like, as well what are they used for electrically?
I usually buy a troy ounce (99.99%fine silver) when I need my Ag, when only dissolving a few grams from one of these bars the solution is colorless,
however when the entire ounce is dissolved the solution is a bright blue as a result of copper impurities. Just a warning for all of you who make
AgNO3 from silver bars, that copper is a major impurity.
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Lambda
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Bright blue ?
Rogue chemist, 1 troy ounce = 31.1034768 grams. So at an impurity of 0.01 %, assuming it is all Copper, you will get 31103.4768 milligrams / 100.00 %
* .01 % = 3.11 milligrams of Copper. I am surprised that this small amount would color your solution bright blue, for it's only about 9
milligrams of Cu(NO3)2 anhydrouse. But maybe you are using as little as 100 ml concentrated Nitric acid to dissolve your Silver in. This would then
have a Cu (NO3)2 concentration of more than 90 milligrams per Liter. This figure then starts to explaine your bright blue color.
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Mr. Wizard
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| Quote: | Originally posted by rogue chemist
Do you have any pictures of these connectors? I am not sure I know what they look like, as well what are they used for electrically?
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Here is an image of my junk pile. Any power relay (contactor) used to switch heavy current will usually have a Silver contact point, as they
don't corrode or oxidize like other metals, forming a high resistance contact. Almost all switches have some silver in them, which is why the
price is high. Often the metal under the silver button is brass or copper, but it is also silver plated to improve the connection. Purifying the
metals is another subject, and obviously there will be lots of Copper, Zinc and others
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The_Davster
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Thanks Mr.Wizard, exactly the pic I was hoping for.
Lambda: My bad, my silver is only 99.9% fine silver, not 99.99%, oops. I dissolved a bit under a troy ounce in only 25-30mL of 70% nitric acid, I do
not remember the exact numbers but it was stoichiometric with 1mL excess nitric and to prevent loss of of nitric during dissolving it was done under
reflux.
After dissolving the silver in 70%, there was a distinct blue color to the solid in the bottom of the RBF. There was not nearly enough water in the
RBF to dissolve all the AgNO3 formed, so the mimimal ammount of water to dissolve all the salts was added and then filtered to remove the indissolved
Ag2S that had coated the bar. This solution was then evaporated and I was left with way-to-blue-to-be-pure crystalls in the bottom of the evaporating
dish. On closer examination of the contents of the dish, it appeared that a 'skin' of impure blue silver nitrate had formed a layer over
some nearly pure silver nitrate crysals with 5mm distance between the impure and the pure. These were separated by hand and the impure was dissolved
and allowed to evaporate again. The same layers formed and I was again able to separate the pure from impure by hand. I ended up with 20g of nearly
transparent silver nitrate crystals with only the slightest hint of blue and 20g of the bright blue copper contaminated silver nitrate crystals. The
silver was reclaimed from the bright blue ones by reducing with copper wire yielding the finest of silver crystals, which surprisingly were able to
react with 70% nitric at room temperature.
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Twospoons
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Silver at $7 an oz is too cheap for extraction from circuit boards, where its mixed with a lot of other stuff, making extraction difficult.
Even the photoprocessors find it barely worth extracting the silver from the spent photochemistry, and they already have the stuff in solution!
I like the idea of melting big contactors though! I believe some of the big (like 200 amp or more) HRC fuses also use silver as the fuse element.
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hinz
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Another good silver source is silver cutlery.
It's mostly an alloy of aprox. 8 parts silver and 2 parts copper. (common silver alloys are 800/000, 835/000 and 925/000) Silver knives mostly
have a steel blade and a silver handle, silver is simply too soft.
Contacts are very pure silver because any inpurities decrease the conductivity ==> worser contact = more heat ==> melting contact.
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jimwig
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Dear DrF.
This man knows about precious metals recovery.
http://webpages.charter.net/kwilliams00/bcftp/front.htm
I have been into this theoretically for a while.
The best book I have found is
The Recovery and Refining of Precious Metals by C W Ammen.
I also have some ref material on refining, assaying, etc.
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Fleaker
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Good sources Jimwig. Ammen's book is very good, but also hard to find.
The website is great except for his production of the sodium/mercury amalgam. I can tell by just looking at it that it won't work.
I dabble in precious metals reclamation and refining via wet chem or electrolytic apps and I'd be glad to offer experiences/info/procedures.
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Eclectic
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Actually, the electolytic production of dilute sodium amalgam should work just fine. It was the basis of an industrial NaOH production process for
more than 50 years, and when the EPA shut it down, resulted in a mercury glut and dumping on the world market.
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Fleaker
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So the sodium hydroxide solution containing the water isn't going to react with the sodium containing mercury amalgam?
You'd have to be putting a lot of amps into the system before you'd saturate the mercury (because you're losing sodium all the
time-the saturated lye solutions gradually becomes less and less concentrated (more H20) which reacts with the sodium making more and more hydroxide)
As I said, high amperage would overcome the problem.
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Fleaker
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So the sodium hydroxide solution containing the water isn't going to react with the sodium containing mercury amalgam?
You'd have to be putting a lot of amps into the system before you'd saturate the mercury (because you're losing sodium all the
time-the saturated lye solutions gradually becomes less and less concentrated (more H20) which reacts with the sodium making more and more hydroxide)
As I said, high amperage would overcome the problem.
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Eclectic
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Something to do with high hydrogen overvoltage on mercury surface. In the mercury cell chloralkali processes, voltage is run the other direction in
the denuding cell to speed up the reaction of the amalgam with water to form NaOH solution.
http://en.wikipedia.org/wiki/Sodium_amalgam
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jimwig
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guys - i have not tried the sodium process but this was in response to reclaiming precious metals.
someone take a look at the web site that I gave the link to.
Doc Williams is assayer and miner in Costa Rica and he knows what he is talking about.
And BTW you can Ammen's book via interlibrary loan all the place.
where are you at - the state as I will tell you closest library holding Ammen's book.
http://firstsearch.oclc.org/WebZ/FSFETCH?fetchtype=holdingsb...
paste this and see what happens.
this should bring up a list of libraries that own a copy.
there are over a hundred libraries that have Ammens' books. He wrote several.
JimWig
[Edited on 29-7-2005 by jimwig]
[Edited on 29-7-2005 by jimwig]
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Fleaker
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I already have his books on refining, sandcasting, and metalcasting in general and the refining one was the most useful for me. After trying to get it
through the library system, I just asked a gold refiner for a copy of it.
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tom haggen
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some old welding rods fell into my lap today. They are only about 5% silver though. However, I have about 20 pounds of this alloy. If there was away
to separate the silver easily from this compostion I would be sitting on about 16 ounces of silver.
[Edited on 5-8-2005 by tom haggen]
N/A
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neutrino
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What else is in them? You could always add a lot of HCl and hope for the best.
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tom haggen
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My bad. I forgot to mention that it is alloyed with copper, and possibly some palladium.
N/A
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12AX7
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Couldn't ya electroplate out in HCl? Copper goes across the solution and plates out a sponge, metals above H+ stay in solution, Ag presumably
falls to bottom as AgCl. Unless it polarizes the anode, in which case nevermind.
I'm guessing Pd would plate across, so if there is any, I guess you'll want to do the usual inquartation with HNO3...
Tim
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Mr. Wizard
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| Quote: | Originally posted by tom haggen
some old welding rods fell into my lap today. They are only about 5% silver though. However, I have about 20 pounds of this alloy. If there was away
to separate the silver easily from this compostion I would be sitting on about 16 ounces of silver.
[Edited on 5-8-2005 by tom haggen] |
Are they a coppery flat stick about 3mm (1/8" wide and about half as thick,
30-40 cm long? It could be what they called silver solder in the air conditioning and plumbing trade. They also might contain some Phosphorus, as
their other name is Sil-Phos. I think it's added to reduce bubbling or something like that. Take it into consideration when you are dissolving it
in acid.
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Fleaker
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Mr. Wizard is right. They do contain some phosphorus to prevent excessive oxidation (just like phoscopper used when casting copper). I've silver
soldered a little, and it's nice to have for joining things; you might want to keep it in case you need it.
If you have a furnace and know how to use it, you could remove the phosphorus in an oxidizing atmosphere, then add another reducing agent (activated
charcoal perhaps?). There's also the Parks process, something could be done there I suppose.
Remember to increase the amount of copper in it (if you plan on electrolytically separating it: 95% or better Cu). Alternatively, you could just
digest in nitric and go from there.
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