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Nickel Phosphate precipitate removal by filtration

Would it be possible to recirculate the electroless nickel bath through a filtering system for removal of Nickel phosphite (phosphate) precipitates. It seems that removal of a precipitate as soon as it is formed would extend the life of the plating bath?

Russell Pickett
consultant to a company trying to resolve this problem - Butler, Tennessee, USA
2007

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2007

It's not so simple. The phosphite byproduct formed in EN baths remains in solution; it isn't directly filterable. You don't want to remove nickel nor form a nickel-containing hazardous waste, so the phosphite is precipitated with something else which doesn't contaminate the EN solution. As solubility is a function of temperature, the EN is purified in a separate, reduced temperature tank. A highly purified grade of Ca(OH)2 or Mg(OH)2 may be used to precipitate the phosphite and excess sulphate, which is then rinsed several times with DI water to recover nickel and make the precipitate non-hazardous waste. The concentrations are adjusted and then the EN is returned to the plating tank through a heat exchanger (which recovers heat from the next batch of EN to be purified. This general process has been used since the 1950's, e.g., see 'Processes of Regenerating Chemical Nickel Plating Solutions' ÿ G.A.T.C., US Patent 2886451 (1959).

Anion exchange resins are another means to remove phosphite ion. "Electroless Plating" (Mallory & Hajdu, eds.) [on eBay , Amazon, or AbeBooks affil links] gives the following references:
K. A. Parker, Plating & Surface Finishing, vol. 67, p. 48+ (March 1980),
F. Levy and S. K. Doss, ibid., vol. 74, p. 80+ (Sept. 1987).

A combined technique (IX & precipitation):
http://www.p2pays.org/ref/21/20249.pdf

It's probably best to contact the EN suppliers of extended-life baths (not all EN solutions are suitable). Some also supply purification systems. Atotech has a patented EDEN (ElectroDialysis for Electroless Nickel) process to extend bath life.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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2007

Filtration removes suspended particulates. Any chemical compounds that are dissolved requires another method of treatment.

The removal of breakdown products to recycle or prolong the life of electroless nickel baths has been the subject of much research over the past twenty years. Several suppliers will reprocess solutions or sell equipment to perform this function in plant.

Check with the supplier of the EN solution for their insights.

Gene Packman
process supplier - Great Neck, New York