# silver recovery from x-ray fixer



## elfixx (Nov 6, 2011)

I came accross some x-ray fixer solution lately and tryed to get the silver out by using some kind of cell using a graphite anode and titanium cathode at about 5v and 3amp. The cell produced a black/brown sludge which is probably silver sulphite, which I understand Is quite a pain to convert to metalic silver, is there a better process to directly plate out metalic silver out from this type of waste?


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## butcher (Nov 6, 2011)

maybe cement on steel wool?


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## elfixx (Nov 6, 2011)

Metalic silver would deposit on steel and not the sulphite compound? If that is is the case should I then process the silver/steel whool in nitric or would there be a better way to go?


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## goldsilverpro (Nov 7, 2011)

The problem with plating is that the silver thiosulfate complex in the solution is negative and is repelled by the cathode. Silver is therefore depleted quickly at the cathode surface and that's when the sulfide is created. All the commercial plating units for fixer have rotating cathodes. The creates a shear action at the cathode surface, which continually provides fresh silver solution to it. Most of these units have a cylindrical stainless drum as the cathode. Some have a series of rotating stainless plates.

Vigorous agitation may help. I've also thought of circulating the solution though a pump and directing the outlet on the cathode. Anything you can do to provide fresh silver solution to the cathode can help. A stagnant cathode/solution system won't work, as you have discovered. A rotating cathode is best.


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## elfixx (Nov 7, 2011)

So a rotating cathode should provide enought stirring to avoid formation of sulfide and would start to deposit almost fine metalic silver?


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## Juan Manuel Arcos Frank (Nov 7, 2011)

GSP is right,take a look to silver´s content in your fix.

If time processing is high sulfurization reaction accelerates producing a huge silver sulphide mud.

What silver concentration do you have in your fix?.How many time did you process your fix?.

Regards.

Manuel


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## luigi2004 (Nov 13, 2011)

Hi!!!
For better silver plating do not get over than 1 volt and 1 ampere for a cathode surface of 100 x 20 centimeters.
If you use a pump, it has to be built with no metallic parts, because the fixer will corrode the pump and will be contaminated.
If you dont want to deal with the rotating cathode you can use a plastic rotating blade in the middle of the tank (20 rpm) and a stagnant stainless steel cathode. 
Luigi


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## goldsilverpro (Nov 13, 2011)

luigi2004 said:


> Hi!!!
> For better silver plating do not get over than 1 volt and 1 ampere for a cathode surface of 100 x 20 centimeters.
> If you use a pump, it has to be built with no metallic parts, because the fixer will corrode the pump and will be contaminated.
> If you dont want to deal with the rotating cathode you can use a plastic rotating blade in the middle of the tank (20 rpm) and a stagnant stainless steel cathode.
> Luigi



With those cathode dimensions (20 x 100 cm - about 8" x 40") at 1 amp, it would take about 7 weeks (24/7) to build up 1/8", a silver thickness I have seen many times on those stainless drums. That doesn't sound right to me. Did you mean 10 x 20 cm?

The correct current density is inversely proportional to the silver concentration in the solution. The more silver, the higher the current density, and visa versa. If too low, it takes too long. If too high, you start producing sulfide.


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## luigi2004 (Nov 13, 2011)

GSP:
Thank you for your deep knowledge and to share it in this wonderful forum.
A friend of mine uses a stainless steel cathode of 20 cmts x 100 cmts and an anode covered with graphite of the same dimentions in a plastic drum with 200 lts of fixer (Roughly 50 gallons)
It has a rotating plastic blade in a wooden pole with a DC motor with gear reduction and runs as I said at 20/30 RPM
Its take 3 or four days running at these settings (1volt and 1 amp) and the silver plating is lovely.
The thickness does not exceed 1 mm but the fixer does not react to the SNa when he finish the running of the machine
I do not know how to post some pictures of the machine, but if some one helps me to do it I will post them with pleasure.
I personally run a stainless steel rotating drum with also lower settings to avoid the nightmare of the silver sulphide.


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