# silver fixer



## Kats12 (Oct 17, 2012)

Hi all again.
I have a question regarding silver recovery from fixer solutions.
There are 2 types of electrochemical recovery processes.
First is when you have tubes with graphite electrodes, a pump, and a converter of DC voltage i think 2-3 V , and around 20-30 A of electricity. This is slow as shi* it takes 2 weeks to recover 2kg of silver.
The fast one is consistent of some sort of a rotating electrode I think it is made of titanium or inox metal. I belive the voltage is the same and the amperage is around 30A.

If some of you have some experience with it, please be so kind and explain me how to construct a faster method or if there is some link on the net with specs for building it.
Thanks in advantage as always 8)


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## Kats12 (Oct 25, 2012)

What? 
No one knows...
unbelievable!


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## goldsilverpro (Oct 25, 2012)

Kats12 said:


> Hi all again.
> I have a question regarding silver recovery from fixer solutions.
> There are 2 types of electrochemical recovery processes.
> First is when you have tubes with graphite electrodes, a pump, and a converter of DC voltage i think 2-3 V , and around 20-30 A of electricity. This is slow as shi* it takes 2 weeks to recover 2kg of silver.
> ...



Here's two pretty good, although general, overviews of methods.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEgQFjAD&url=http%3A%2F%2Fwww.kodak.com%2Fek%2FuploadedFiles%2FContent%2FAbout_Kodak%2FGlobal_Sustainability%2FHealth%2C_Safety_and_Environment%2FPublications_Library%2FJ212ENG-0311.pdf&ei=aIOJUKS3K8Hq2AW72IC4Bg&usg=AFQjCNEp7pUH2sGGb50jhzEJQfQXQXbQpQ&cad=rja
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CD0QFjAD&url=http%3A%2F%2Fwww.scribd.com%2Fdoc%2F50354428%2F175%2FSilver-recovery&ei=24SJUMkwh9DbBYaRgeAH&usg=AFQjCNGO_0Xz-mMP46sAhseSC2q6EFey3A&cad=rja

I've used several methods but the rotating drum cathode units work the best of anything I've used. If used properly, they will deposit 97-99% silver. I've seen it 1/4" thick on the drum. The common steel wool cementation cartridges work but recovering the silver from them is most difficult. I have heard of zinc precipitation being used but have never tried it.

For small quantities, I would experiment with the zinc precipitation, probably starting with 325 mesh zinc dust or zinc drillings. For large quantities, on an ongoing basis, I would get a rotating cathode electrolytic unit. With x-rays, etc., going digital (non-silver), places like large hospitals of large newspapers might have these units warehoused and they might be for sale.


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## Kats12 (Oct 31, 2012)

Hi 
thanks GSP for advice

I've tried with zinc, the content of silver in fixer was 3g/l, but the Zn doesn't work well, at least in HDPE cannister , the cemented silver is too small to be filtered...
I'll try in my 5l pyrex beaker next week, so it might give a better result. The temperature was around 10 celsius, do You think heating beaker up might do the trick?

well regarding rotating cathode..
I'd like to make one, because it is more cleaner method then zn, if someone would be kind to post some pictures how it looks , the anode is carbon , and cathode is stainless steel
i belive... i've been searching net for weeks now and nothing :-(


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## goldsilverpro (Oct 31, 2012)

Somewhere on this forum, I remember a photo of a commercial rotating drum unit but I couldn't find it. The drums I've used were made from about 18 gauge 300 series SS sheet, fashioned into a cylinder about 5" dia x 12" long. They had internal welded SS bracing and a center shaft. The top of the shaft was connected to a reduced gear rotating mechanism, through which a D.C. current was applied. I would guess they rotated about 15-30 RPM. The solid silver was removed by removing the drum and tapping it gently with a hammer. The silver was brittle, easily broke into large pieces, and came loose from the passive SS surface. These slip rings might possibly be used, somehow, to accomplish this.
http://www.mercotac.com/

The purpose of the rotation is to replenish the silver at the cathode surface (cathode film). You might accomplish the same thing by recirculating the solution through a pump and directing the output on the surface of a SS sheet cathode, but I've never tried it. If you try to plate the silver out without good agitation at the cathode surface, you will decompose the thiosulfate to a stinking, black, slimy, non-adherent, sulfide sludge, containing some silver, instead of producing a white solid adherent silver deposit.


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## mda20 (Nov 25, 2012)

Here is a link to a rotating cathode recovery unit.

http://www.aeroindia.net/files/files/ru200p.html


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