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Author: Subject: Electro-refining copper, silver, lead & some others - how do refine lots of pieces at once
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[*] posted on 12-2-2021 at 16:40
Electro-refining copper, silver, lead & some others - how do refine lots of pieces at once

I have lots of small pieces of these metals and I can't really melt them into a single ingot at this time and I've seen some people use baskets to hold lots of pieces to refine all at once, and also act as the conductor to the pieces of metal. So this is what I would like to do but I have a couple questions about this.

I don't have a lot of basket material that I think will work so I am wondering if I can use something like a stainless steel bowl as the basket/electrode and put all the scrap on the bottom and hang the cathode in the top center of the bowl and dip down into the solution. I was thinking I could use some clear packaging tape to cover the entire interior of the bowl (the sides) and leave the bottom exposed to allow contact with the metal to be refined.

What I'm not sure about is what kind of electrolyte to use and how concentrated it should be and should I use different electrolytes with different metals?

I have power supplies where I can control the voltage and amperage (CC & CV supplies) and can go down to 1v. I'm assuming that the lowest voltage that will work should be used, but how does this process selectively choose which metal is transferred through the electrolyte. If there is copper, lead or whatever in the silver, how do I make sure it leaves all that behind? Is this voltage dependent - if I go too high on the voltage, will it carry over some of the contaminants?

The only other way I was thinking this is possible was to use a plastic bowl and put a metal plate on the bottom and run an insulated wire down to make contact with it, then put the scrap metal on the metal plate. If i choose this, is there a preferred metal for this? I have some copper, Al, stainless & normal steel sheet that can be used and was wondering which would be ideal.
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[*] posted on 22-8-2021 at 00:00

I'm not sure if it helps, try looking at sreetips youtube channel he does a lot of silver electrorefining.

I did some experiments, not exactaly on electro-refining, but in electroforming, which is close, from experience, try to limit the current and experiment to curent levels, voltage is important, but I suggest you raise just enough you get good enough conductivity. too much current and your product becomes a fine dark dust and I'm not sure if it ends up being as pure. I know that single grown pieces are very pure. plus, choose the best electrolite and try to keep all clean.

"NOOOOOO!!! The mixture is all WROOOOOOONG!"
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[*] posted on 22-8-2021 at 03:55

As far as I know (which isn't very far) anything that wets/soaks in the electrolyte
but does not allow a significant flow of electrolyte through it
and is not attacked by the electrolyte
will work as a membrane.

porous pot, cloth, glass fibre, polymers, salt-bridge etc.

Thinner (plus greater area in the electrolyte) is generally better as it means lower electrical resistance
PS I doubt that an electrically conductive membrane/basket/pot would work
as the electrical potential gradient within the basket would be zero,
you would be trying to electrolyze the basket, not its contents.
Putting the scrap at the bottom may work but I'd expect the refined metal to fall off the electrode back into the mess at the bottom

[Edited on 23-8-2021 by Sulaiman]

CAUTION : Hobby Chemist, not Professional or even Amateur
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