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Precipitating nickel from enickel dragout
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A colleague of mine asked me to figure out way to remove Ni from Enickel bath dragout. I recommended 2,4,6- Trimercaptotriazine (TMT--Degrussa)as a method because of very high caustic demand for dropping nickel. That option was also considered too expensive. Email from colleague today says ammonia is the cause for high caustic demand. How about sodium sulfide as a Ni precipitant?
Russell Pickettenvironmental consultant - Butler, Tennessee, USA
First of two simultaneous responses -- +++++++
Firstly methods should be employed to reduce drag out and recover drag out for reuse in the operating tank. It has proven practical, in my past experience, to concentrate the drag out and electrowin much of the nickel.
Gene Packman- Great Neck, NY
Second of two simultaneous responses -- +++++++
Sodium sulfide works great. However, people tend to shy away from it because of the possiblity of generating H2S - it's released on acidification of sulfide bearing liquids.
A safer solution that's often used is ammonium dimethyl dithio carbamate. It's sold by
Luster-On Corporation, who has a presence on the site here.
You speak of "high caustic demand" - you are going to have to raise the pH to at least 8 to use any precipitant that I'm familiar with, and I've been treating nickel wastes for a long time.
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Dave Wichern - The Bronx, New York |