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Plating Ni from dialysis waste stream  

June 19, 2008

I'm new to the plating industry and have been reviewing previous forum topics for general background. The idea of using dialysis to recycle nitric acid from EN tank cleaning baths is intriguing. Can the relatively low acid, high Ni effluent be plated to reduce Ni content, or is neutralization and precipitation the only option? What would be required to add to the waste stream to get viable plate out?

Leo Sharkey
Plating shop employee - Fridley, MN, USA

Hi, Leo. I haven't tried this personally but nickel is a difficult material to plate out under less than ideal conditions (including low concentration). And nitric acid is, to my knowledge, a bad solution to plate out of because it is such a powerful oxidizing agent. I think you tend to destroy nitric acid rather than plate nickel, and once it's destroyed you have no acid to plate from :-)

But I'd be happy to hear from someone who has actually tried it.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

How low is the acid? If you are talking about 0.5 - 1%, you might try passing the waste through a bed of a strongly basic anionic exchange resin, in the chloride form. You could plate out of the eluate from such a column. A pH adjustment of the feed solution might be necessary to get effective nitrate removal.

Dave Wichern - The Bronx, New York

The dialysis manufacturers claim 85% recovery, 15% reject for the nitric and vice versa for metals. At a 50% acid feed and perhaps 5 - 10 g/L Ni, that would mean about 7% - 8% Nitric and a Ni content of perhaps 30 - 50 g/L. (There must be some solubility limit on the upper end, but suffice it to say that the Ni content would be fairly high.)

Leo Sharkey
- Fridley, MN, USA