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metal ion removal

I regularly produce an acidic nickel nitrate solution as a by product of plating. Attempts to remove the nickel ions with carbon electrodes and a rectifier have done nothing. How can I plate out the metal completely?

warren silverman
amberon corp - brooklyn ny
1998

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1998

Nickel plates well out of highly concentrated sulphate, sulfamate, and chloride solutions. I suspect that the overpotential to plate out of nitric acid is so high that the metal is redissolving as quickly as it plates out.

The only metals I have ever been able to plate out of nitrate solutions are silver and copper, and only then when there is little or no free acid. The deposit for silver (refining method, see Thum or Moebius cell) is lovely little crystals. The copper deposits are sometime trees, sometimes slightly more rounded. Neither is what you would call a "good" functional plate.

Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona

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1999

Nickel will only plate out at high efficiency if the pH is greater than 2, and preferably above 2.5. Otherwise the cathodic current plates out hydrogen gas.

You might try neutralizing the acid to a pH of 3-4 before electrowinning. However as B. Vins previously pointed out, deposits from nitric acid are usually acicular crystals and trees. Please be careful that trees do not short out the cell and potentially cause a fire.

Lyle Kirman
consultant - Cleveland Heights, Ohio

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