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topic 5789

Waste treatment of Solder Stripper (ammonium bifluoride and hydrogen peroxide)

February 10, 2014

Q. Is there any way to treat Solder Stripper 200 consisting of ammonium bifluoride and hydrogen peroxide? Batches of this tend to kill my ORP readings (low). Since H2O2 is an oxidizing agent shouldn't this raise the ORP? Maybe it's the additives in the tin?
Any info is appreciated. Thanks

Bob britton
- Sanborn New York usa

February 19, 2014

A. I don't believe ORP is very effective at monitoring H2O2 levels.

I'd suggest raising the pH to 4 - 5, then neutralizing the peroxide with sodium metabisulfite. I used to monitor peroxide using the pertitanic acid method. Dissolve titanium sulfate (10% or so, w/v) in 1:2 sulfuric acid, then combine 1 ml this solution with your waste. A yellow color indicates peroxide.

When all the H2O2 is gone, raise the pH to about 9 with lime. Then, add Calcium chloride until there is about 400 ppm excess Ca2+ in the liquid. This should remove F- down to about 15 ppm.

If metals are present (likely) you will need to add a precipitant like Na2S or DTC to drop them.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

July 22, 2015

Q. How can we recover Tin from Tin Stripper of PCBs?
We have tried various methods but due to filtration issue, we can't reach at final stage.
By Sodium Hydroxide method, cost becomes high which makes its less viable.

Hardik Patel
Meghachem Industries - Ahmedabad, Gujarat, India

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