Regeneration and decontamination of a nickel citrate complex in spent electroless nickel plating solutions

The possibility of citrate precipitation by excess metal ions in alkaline solutions suggests the use of Ni(II) together with OH- to precipitate a Ni(II)-citrate complex-from spent electroless plating solutions. After treatment of the precipitate with acid, excess Ni(H) can be removed in the form of insoluble Ni(OH)(2). The solution of the Ni(II)-citrate complex can then be reused,for electroless nickel plating. During this procedure the additive adipate is not regenerated. For decontamination of spent electroless nickel plating solutions Fe(III) can be used as Ni(II)-carate complex precipitant.