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Ni recovery by electrolysis

 

We have two type of spent Ni-baths: * nickel sulphamate baths (20-40 g Ni/l, 100 g SO4/l, pH 4-6) - electroless nickel baths (6 g Ni/l, complexing agents, 100 g SO4/l, hypophosphite, NH4).

We consider electrolysis to recover the nickel, followed by precipitation to fulfill our Ni-limit of 3 ppm. In a simple lab test it turns out that the Ni from electroless-Ni can be reduced to 3 g/l after 8 h of electrolysis at pH 4. However with Ni-sulphamate no Ni is recovered at the electrode at pH 4. The solution only turns from green to black color.

Does anybody have suggestions how to improve this.

Thanks,

Robert de Boer
- Amersfoort, Nederland

My company has been working on a similar application through a local university with the aim of recovering tin. I would welcome the opportunity to further discuss the application and provide further information on the most likely method for success.

Peter Becker
- Ashmore, Qld, Australia

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It sounds like the ball is still in your court, Mr. Becker; don't just tell the readers that you can provide further info on the most likely method for success--go ahead and start providing it :-)

Nickel is a tough one to electrolytically remove to these levels, Mr. de Boer. There are dozens of different brands of electrolytic recovery cells in use on gold, silver, tin, and cadmium--but nickel tends to exhibit the problems you noted at low ppm levels. It may be that you will have to remove the nickel from your waste stream with ion exchange, and then electrolytically remove it from the regenerant where the nickel concentration will be far higher.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

I have come across a Nickel recovery system which recovers Ni from drag out using a Electrochemical Fluidized bed reactor (Electrolytic recovery). The anode is TSIA(Titanium substrate insoluble anode - RuO2 coated) and the cathode is Titanium. The fluidizing media is Glass beads. The anode and cathode are packed very closely and the media provides good mass transfer as well as prevent the growth of dentrites and makes the deposit even. Low concentrations in drag out can be revocerd bythis method and the metal can be removed from the cathode by chiping off or directly using in Nickel bath as anode. This system was manufactured by a firm in UK (I forget the Name). Probably you can give a try.

Karthik
- Singapore