Waste Water Treatment of Electroless Nickel Plating
Can anybody suggest an effective technique for treating spent bath (electroless nickel plating) from our process bath. We use nickel sulfate, sodium hypophosphite, wetting agents and ammonia for pH adjustment in the process. Currently, for our waste water treatment we use CaCl2, NaBH4 and adjust the pH to 9.0, precipitate settles and then filter press. We still have 50 to 100 ppm nickel.
Could anybody please suggest any more effective treatment techniques or precipitating agents that might be more effective to remove nickel. Your suggestions are highly appreciated. Thanks in advance. JosephineJosephine C. Lee
- Taipei, Taiwan
Here in the U.S. the problem has largely gone away for plating shops since many vendors take back the exhausted solutions for recycling. But two non-chemical methods you might wish to consider are:
1). Electrolytic plate-out (in practice this is often used in combination with ion-exchange; ion-exchange removes nickel to very low ppm, then the resin is regenerated and the regenerant and backwash solutions are what is actually electrolytically treated).
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Hello Josephine, I believe that electroplating is the method of choice. There is, however, some things to consider. The effectiveness, where most of the energy is used to plate metal is greatest in a very narrow pH-range. Between 8.5-9.
You must use "large area, steel wool" cathodes. When this solution gets electroplated some kind of organic is formed as a result of anodic oxidation. It smells almost like formaldehyde. I put in carbon filters in the plating equipment and let the solution go through these. After plating is done, there is a question of the hypophosphate. If it is possible to discharge then ok. Otherwise you have to treat it with ferric chloride or your carbonate and filter press it. SvenSven
July 28, 2008
You can use vacuum distillation for your plating wastes coupled with IX and other technologies you can recover and reuse much of your electroless nickel plating process chemistryDavid Delasanta
- Worcester, Masssachusetts
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