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-----Recycling of Chrome Stripping solution (HCl)
Q. I am working in a plating shop where we strip chrome with HCl. The leftover (Cr+ HCl) is waste and we give it to a dumping site which costs lot of money. Is there any way we can reuse this waste or any process where we can convert this waste into useful product. Thanks.
Farhan Patel- Bharuch Gujarat, India
December 11, 2022
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A. Hi Farhan. It's admirable to reduce waste and recycle where possible, but chromium is not a precious metal so as far as I know there is no remotely feasible solution. The reaction ...
6HCl + 2Cr ⇨ 2CrCl3 + 3H2↑
... moves very strongly to the right, and is essentially irreversible. Further, applying electricity to the CrCl3 is likely to convert the chrome from the relatively harmless Cr+3 state to the toxic Cr+6 state.
Unfortunately, I think the thing to do is to treat the waste with lime or NaOH via conventional waste treatment chemistry to precipitate the chrome as a hydroxide, filter it, and landfill it. Hopefully the high chloride filtrate will not be a disposal problem.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
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A. Hi Farhan
This is not a method and not a recipe. I don't know if it works, if anybody does it, or if it is economically reasonable. It's just an idea that might be worth checking.
In theory, Chromium Chloride should react with Phosphoric acid (H3PO4) to form insoluble Chromium Phosphate. In a small beaker [beakers on
eBay
or
Amazon [affil link] try to add a little Phosphoric acid to your spent solution (use PPE and good exhaust/ventilation). Probably it is possible to precipitate Chromium Phosphate and filter it out.
If it works (or does not work) - please let us know.
Good luck,
- Winnipeg, CANADA
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