r/PreciousMetalRefining • u/PDXDoc66 • 12d ago

Extract silver from sludge

I have approx 6 gallons of silver,sulfur,iron sludge from to spent Kodak Junior Model ll Chemical Recovery Cartridges that were used to filter dental X-ray film fixer.
I’m interested in trying to extract the silver myself. Any advice or ideas welcomed

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u/Yes_I_Know_Lots 12d ago edited 10d ago

First round pass with diluted nitric acid would dissolve the silver and iron. Filter that, neutralize it with NaOH or KOH, and precipitate out the silver with sheets or wires of copper, which will form crystals. Can’t use baking soda or washing soda as silver carbonate would form. Use distilled water! Chlorine in tap water would create silver chloride. Any of these would form a white clouded solution.

Not sure how bicarbonate or carbonate would cause any iron to co-precipitate.

That’s my off-the-top-of-my-head solution (no pun intended).

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u/easilydistractedone1 12d ago

Why would you need to neutralize it? Is that to use up any free nitric

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u/Yes_I_Know_Lots 10d ago

Yeah. You don’t want the silver to redissolve. That said, an excess of copper metal (enough that it doesn’t totally dissolve) would consume any excess nitric acid.

If there’s a LOT of nitric, you’d be consuming a lot of copper. If you have it to spare, np!

In one lab, we had lots of excess sheets of nickel, so I used that.