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"Treating Acid Waste"

March 9, 2010

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

First of three simultaneous responses -- March 12, 2010

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
James Totter, CEF
- Tallahassee, Florida

Second of three simultaneous responses -- March 13, 2010

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
Dave Wichern
Consultant - The Bronx, New York

Third of three simultaneous responses -- March 13, 2010

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 is the way to go. Slowly, with mixing, while watching the temp.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri

March 16, 2010


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 25, 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

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