deplating silver from silverplated items

[solar_plasma]

i did at test, 100 ml distilled water, 20g sodium persulfate, 1g silver from cementing, after adding silver
to the solution, the reaction starts, silver was converted to silver oxide, it was dark on the ground, after few minutes, the solution
was gray/black in color an was not transparent.

Just found something interesting related to this post: http://en.wikipedia.org/wiki/Silver(I,III)_oxide

and I read, that there always will be some persulfate left when copper is edged in persulfate. Is it possible, that if pure CuSO4 is used, the sulfate partly would be reduced to persulfate? Is copper persulfate green? ..since my solution shifts between green and turkise and sometimes a black powder occurs on the silver.

Edit: green colour is probably nickel, black powder probably cementet copper

Whatever....somehow it works.

 

[ilikesilver]

curiosity killed the cat, if AP will disolve copper, then why wont AP work on this same scenario? tim

 

[etack]

curiosity killed the cat, if AP will disolve copper, then why wont AP work on this same scenario? tim

You mean like these? these came from 3phase connectors and had two long gold pins in them 8) .

if they are all cooper use them to cement your silver. If you look for silver plate when your out only buy silver over copper so you can get the silver back that way. the other silver plate you can throw into old Ap and have it work on it that way. There is no cheap what to strip silver or it would be bought more frequently as silver bearing scrap.

Eric

You want to keep as much of the junk as you can out of your silver. The white "brass" is full of other stuff lower on the series chart so it will cement out Cu into your silver. in the AP he silver will flake off and sit at the bottom of the bucket. this can also be done with used sulfuric acid that has water in it.

Eric

 

[solar_plasma]

I see the benefit of this cell in it's safety and thereby I agree with butcher. This is a process I can do at home with good conscience. Most of the other processes I prefere to do under real laboratory conditions.

For sure my silver isn't pure, but it is light grey and sparkles. If it is not pure enough for further electrorefining, I thought of treating it with AgNO3 or AgSO4 to dissolve basemetals, has anybody tried this?

The gained copper will be contaminated with silver and basemetals. I will keep it and thought of using it for inquartation, later I have come so far. Ofcourse I will test it before I do that.

IMPORTANT NOTE: Don't use the flatware for cementing like it is described on http://www.experimentalchemie.de/versuch-051.htm, but only clean cobber !!! Since most of the flatware contains zink and nickel, this will cement the Cu from your electrolyte, which is getting more and more green and at the cathode the cobber becomes more and more dark from impurities. The cemented copper will contaminate the cemented silver, which gets a brownish tint. If this happens, you can add a large amount fresh CuSO4. You will get light red copper at the cathode again.

Sooner or later the electrolyte will be saturated by zink and nickel. I will have to find a proper way to handle this.

Edit: From a profits view, it may be better to mill the silver off mechanicly if ugly white brasss is beneath the silver and then process it the wet way. For plated cobber this method will work cheap and easy. Just use a small distance, high electrolyte concentration, maybe a bit sulfuric sometimes and have a large electrode area. Then you can run it with 3 V and 10 A. Then the cobber cristalls will be very nice too.

 

[solar_plasma]

Well, I have learned much from my version 0.x cells, now I present my version 1.0. First time in progress. 8)

At this time it runs with 5V and 4A.

 

[solar_plasma]

The new boxed cathode design helps avoiding floating lumps of cobber contaminating the silver.

 

[solar_plasma]

But it is still a nasty work!

 

[butcher]

I Do find the experiment interesting.

 

[solar_plasma]

Thank you, Butcher!


Safety note: There is not only nickel, but probably also cobalt (violett sulfate) in some flatwares. Cobalt sulfate is category 1 cancerogene! Make sure not to let aerosoles getting into the air. I covered my cell with a plastic bag.

 

[solar_plasma]

I advise, equal to good practice with other scrap, as far as possible to use equal items as the anode. Flatware is made of most different alloys, which naturally react very different. Some finishes, like "mangasil", which becomes black without being attacked very much, needs to get brushed with a steel brush once in a while. I guess, that the black layer is passivating them a bit.

 

[solar_plasma]

I need your thoughts:

I am thinking of using an aquarium filter pump with weak flow to suck silver sufate containing electrolyte (max. 8g/l - because of the other sulfates, much less) out of the cell, let it pass through some copper in a larger vessel with extremely low flow and back to the cell. In and out should have the same distance from the electrodes, maybe behind the anode.

Benefits: More liquid=more silversulfate dissolvable / continuously fresh electrolyte / less contact with the cathode copper / less contact with the non-copper basemetals at the backside of partly dissolved anode

Do you think, there is a good chance, it would work or have I missed something?

 

[solar_plasma]

Update:

Now I use two cathodes, one in front of the anode and one behind, because I encountered cementation on the back of the cathode. The cell runs constantly with 3,3V at 10,7 A, no gas and it stays pretty cool.

 

[solar_plasma]

Everyone who is interested in this subject, http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=54&t=15614&p=185238#p185238, in the bookhttp://uctm.edu/departments/MCMT/BG/E-library/Extractive_Metallurgy_of_Copper_-_G._W._DAVENPORT.pdf in chapter 16 is all you need!

thiourea/HCl is not absolutely necessary in small set up's with my cathode construction, which I now again have furtherly improved
[thiourea is a compound in some silver cleaning bathes, cat.3 cancerogene...which should not be the biggest problem in this poisonous heavy metal witch brew]

I am not trying to strip the silver anymore, but I just let the whole anode dissolve

I don't cement anymore over night, I just let it work.

I reiuvenate the electrolyte by thinning with washwater from the bucket in which I wash the cathode once or twice a day and by adding sulfuric

when the ampere are falling, I adjust with small amounts concentrated sulfuric.

The cell works and it's eating like a swarm of piranhas. 8)

 

[solar_plasma]

The electrolyte is quite quickly used up with many plated alloys, obviously quite quicker when there is a high zink content. This had to be expected.

To take the washwater from the cathode copper bucket (I added a bit sulfuric from time to time) will not give enough Cu++ cations, though it's nicely blue in colour. My challenge will now be to find the easiest, fastest and cheapest way to form new CuSO4. As far as I read on the forum, this is not as trivial as it seems to be. I think of five possibilities:

Cu (powder) + H2SO4 + H2O2 (read also Caro's acid! - only use diluted agents! only small amounts H2O2! Handle with care!) EDIT: works fine to clean silver-copper blends (brown-grey), the remaining CuSO4 solution will probably contain a little AgSO4 and will be added to the electrolyte again. Acid fumes and violent reactions possible!http://en.wikipedia.org/wiki/Piranha_solution
2 Cu + O2 -> 2 CuO // CuO + H2SO4
Cu + HNO3 + H2O2 // CuNO3 + NaOH // CuOH + H2SO4
Cu + AP or A/Cl // CuCl2 + NaOH // CuOH + H2SO4
Cu + Na persulfate

Ofcourse all will work. All have disadvantages. I just don't know, what is most practical. I will find out, though if anyone likes to comment, you are welcome.

Since electrodeplating is very fast in the beginning and than slows much down, I could imagine, that it would be a good solution to simply slowly let dissolve the residual metal pieces in acid in order to get the last gramm of silver.

Another thought of mine: Since the used electrolyte is low in Cu++ (close to nothing) and probably high in nickel, maybe it could be used with a nickel cathode on the mostly stripped anode. The anode slimes will then be a blend of cobber and silver and would have to be dissolved in HNO3. But this could at least save some amounts of acid, since Ni and Zn are separated. But since I have no nickel plates, I cannot try it soonly.

BTW to all, who think, they could earn money on this, - forget it :lol: I have bought the scrap for under 50% of spot price and all the gloves, chemicals and electricity alone have eaten the profit.

 

[butcher]

copper oxide mixed with silver oxide, can be formed from these powders, wash well dry and incinerate.

The copper oxide will dissolve easily into most acids.

Silver sulfate has a low solubility with other metals in solution there may not be much silver in solution, (you always can use the chloride test on a small portion).

copper oxide will also dissolve in HCl, where silver forms the insoluble chloride.

Decisions, what do we think will work best for our situation.

 

[solar_plasma]

copper oxide mixed with silver oxide, can be formed from these powders, wash well dry and incinerate.

I think this one will be a good choice for bigger amounts of blends with much copper and little silver. I used 4M H2SO4 (about 35-40% I guess) with very small amounts of 33% H2O2 carefully added on estimated 60-80% silver and it worked rapidly. Though next time I will dilute the H2O2 first. Although I expected possible violent reaction and ofcourse started with a tiny probe, I was surprised on the generated heat. Thanks, Butcher! I will try this.

 

[solar_plasma]

solar wrote:

The new boxed cathode design helps avoiding floating lumps of cobber contaminating the silver.

The recovered brown powder on the left yielded about >50% silver after the 1. refining by dissolving in HNO3 and cementation on copper. I will post the yield from the light grey powder on the right as soon as I have processed it.

 

[rewalston]

looks good solar, can you describe how you constructed your sell? I have a lot of silver plated "silverware", can't sell it or trade it so might as well play with it.

Rusty

 

[solar_plasma]

If there is only copper beneath, just run it like a traditional copper refining cell. If there is Cu-Ni-Zn beneath, it is best to stop before the reaction mostly attacks the basemetals, because they quickly foul the electrolyte. Otherwise, you could just use fresh electrolyte every day, if you have enough CuSO4, then you can just go on until the anodes are completely dissolved. Then you have a lot of liquids to treat for reuse.... nasty.

You could hammer the pieces flat to have a homogen distance.
The distance between anode and cathode should be short (higher Amp and less electrolyte), but long enough to prevent short circuits. Under 2V at 6-8A worked fine for 12 big spoons. If you use a membrane like goretex, it will become very slow, but you get small hard and dense copper crystals at the cathode without using additives. I never tried additives like thiourea and bone glue, that's what they use in plants to get a dense copper deposition. The cathode can be made of copper- or stainless sheets. Also in plants they circle fresh electrolyte into the system all the time and treat the used electrolyte for reuse. The system should not get to cold, I think 30-40°C are fine. Prevent producing H2 by setting the voltage down, - it would be a loss of energy and produces a fine invisible fog,that probablyis not very healthy. Therefore cover the system, when you leave it after loading or cleaning.

When the electrolyte is loaded with silver sulphate, remove all electrodes and cement it oout on pure copper sheets, then your electrolyte will stand a little longer before the coppergets more and more replaced by zinc and nickel.

Use a big 100-200ml syringe to clean up copper or silver that could float around every some hours.

 

[jmdlcar]

What was the Voltage used in this Cell? That the only thing I'm not sure of is it 5 or 12 volt?