Metal finishing Q&As since 1989

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Recuperation of precious metal by electrolyse (gold and palladium)

July 18, 2009

Hi,

We are a small company dealing with the precious metal plating on jewelry articles (gold and palladium). One of our problem is the recuperation of precious metal in the container used for rinsing. A constructor proposes to us an installation for the palladium recuperation by electrolyse but it's too expensive for us (~ 10000 USD !).

The solutions we have to refine :
- water rinsing from alkaline gold bath (KAuCN2)
- water rinsing from acid gold bath (KAuCN2)
- water rinsing from acid gold bath (KAuCN4)
- water rinsing from ammoniacal palladium bath

Does someone have any plan for a machine to refine these different solutions (cathode to use, position of cathode, generator, intensity, etc ...) ? Or maybe there is some books which explain the electrolytic refining for these solutions ?

Thanks in advance ;)

François Pignon
Plating shop employee - France

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You can likely precipitate the palladium, as the metal, by adding a suitable reducing agent, formic acid or sodium borohydride might work.

The gold can be recovered by passing the Au bearing rinses through a bed of an anionic exchange resin, then incinerating the resin. Or, you could concentrate the rinses via evaporation, adjust the pH till it is alkaline, then add some excess cyanide and plate the Au out.

Dave Wichern
Consultant - The Bronx, New York
July 24, 2009

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August 10, 2009

For small quantities, the most convenient approach to use is often ion exchange resins.

The resins can reduce gold or palladium to less than 0.1 mg/L and concentrate them for recovery. 50-100 grams of gold per liter of resin is commonly achieved.

Palladium can also be recovered this way, but the grams of metal per liter of resin is lower, and sometimes a different resin is used.

When exhausted, the resin is sent to a refiner. The resin is burned, which destroys any cyanides and the gold or palladium is recovered from the ash.

Lyle Kirman

Lyle Kirman
consultant - Cleveland Heights, Ohio

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Hi Dave,
Could you explain further on formic acid being a reducing agent. Wouldn't it be rather a palladium salt precipitation? Thanks,

Guillermo Marrufo
Monterrey, NL, Mexico
September 24, 2009

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respected sir,
you just add some NaOH-caustic soda [affil links] & zinc dust [on eBay or Amazon] to your cyanide solution. Stay whole solution for one night. Filter it. Now you can treat the residue for getting gold and pd.that is refining process.

Bhupesh Mulik
- Mumbai, India
October 30, 2009