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Treating Acid Waste

I am treating old stripping solution. Under a scrubber of course. A solution that had been sitting for a long time with a pH of 0-1. When I added soda ash and sodium hydroxide I added very slowly and it took a very long time. problem is when it cooled it formed some kind of salt and it freezes in pipes and tank. Is this from all the sodium added? only very hot water will dissolve the crystals that form.

Brian Smith
Employee - Newark, Delaware, USA
March 9, 2010

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First of three simultaneous responses --

I'd guess that the problem isn't the sodium, but the carbonates being formed by the soda ash (sodium carbonate). Hard to say since you don't tell us what kind of stripper.

James Totter, CEF
- Tallahassee, Florida
March 12, 2010

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Second of three simultaneous responses --

What acid are we talking about? That's important.

If it is sulfuric acid, I'd suggest neutralizing it with magnesium oxide/mag hydroxide. MgSO4 is lots more soluble in water than Na2(SO4).

Dave Wichern
Consultant - The Bronx, New York
March 13, 2010

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Third of three simultaneous responses --

What is the chemistry of the stripping solution? What metal were you stripping in it? The solids could be an insoluble carbonate from the soda ash that you added. That is my first guess, but I'd need to know what else is in there. You really shouldn't use soda ash for this kind of treatment, caustic soda [affil links] is the way to go. Slowly, with mixing, while watching the temp.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

March 13, 2010

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Brian

If it is a metal(s) stripper, and old, you probably have a bit of metal dissolved in solution. Probably why you are getting rid of the stuff. Neutralize the stripper and you will drop out the formed salts as well as the metals. If you have more, you could dilute first to help keep the salts in solution, or filter as you process to remove.

Willie Alexander
- Colorado Springs, Colorado
March 16, 2010

I'm sorry it is a nitric acid and it could have any heavy metals in it. I'm going for the silver. Another problem I had was when I recovered the silver I got lead chlorides also is there a way to only recover the silver?

Brian Smith
- Newark, Delaware, USA
March 25, 2010