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How to treat spent Nickel solution containing Nitrobenzene Sulfonate

I am wastewater Engineer, I am currently working with a company in Malaysia/Philippines; we receive wastewater at a fee to be treated. Lately we received wastewater -spent nickel solution containing m-nitrobenzene sulfonate which is difficult to be degraded using Fenton Oxidation. I have problem with the color of the solution reddish orange cannot be easily removed. Can someone help me giving some suggestion. Thank you, Anand Saminathan wastewater engineer - Gopeng Perak Malaysia November 21, 2008

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You're dealing with a spent cold nickel stripper. That is one of the most difficult wastes to treat.

You might try, pre Fenton's reaction, boosting the pH to 12+ with NaOH, and using aluminum to reduce the Ni out. Or, sodium borohydride.

Good luck!

Dave Wichern
Consultant - The Bronx, New York
November 25, 2008

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November 26, 2008

Dear Mr Dave,

Thank you for you suggestion. Your are right by the saying that it is one of the most difficult wastewater which I am dealing with.The COD is tested to be approx. 50,000 ppm.
The pH of the solution as received is 12.6. The colour is as per attached photograph.Ni content is about 8 g/l.
After Fenton Oxidation(pH 2.5/fe2+/H2O2/2hr) the COD is only 43000 ppm.

I will try your method.Will this help me to remove the colour? Meanwhile if there is anything at all you would have in mind kindly share with me.

Thank you
Anand
Wastewater Engineer

Anand Saminathan
- Gopeng, Perak, Malaysia

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There could still be some cyanide present. Typically the stripper contains 90 gms/l sodium cyanide and 60 gms/l m-nitrobenzene sulphonate. When the stripper is discarded free cyanide is easily destroyed with hypochlorite, i.e. a solution of chlorine in sodium hydroxide solution. The brown substance is a complex of nickel and cyanide. This complexed cyanide can still be destroyed with hypochlorite but it takes much longer, maybe days. Well, it does in England but your waste is 30°C warmer! The nickel ends up as a black precipitate, probably hydrated Ni2O3.
Obviously the best time to do this treatment is before mixing it with any other waste.

Nick Clatworthy
- Whitstable, Kent, UK
January 4, 2009