Nickel Recycling from Spent Electroless Nickel Plating Baths Using Solvent Extraction

Demand is growing for the recovery of nickel from spent electroless nickel plating baths (spent bath). The present authors have been studying the application of solvent extraction to this problem, and their findings are outlined in this review. On the basis of batch extraction experiments, a recycling process was established consisting of two steps: (i) impurity removal, followed by (ii) nickel recovery. In step (i), iron and zinc as impurities in the spent baths are selectively removed using acidic organophosphorous reagent such as PC88A. In step (ii), after increasing the pH to around 6, nickel in the spent baths is extracted using the chelating reagent LIX84I as an extractant aided by a small amount of PC88A as an accelerator. The nickel in the organic phase formed is stripped with 1-2 mol/dm(3) of sulfuric acid in order to obtain nickel sulfate solution, which is reused in the plating process. After the nickel extraction step had been validated by the continuous multistage experiment, in which high efficiencies were obtained during the extraction and stripping, this process was introduced in a plating plant and has been stably operated for more than one year. The bath life extension gained by removing impurities or byproducts using solvent extraction was also studied. Zinc in the strike nickel plating bath used for plating on an aluminum surface treated with zincate solution was found to be selectively removed using acidic organophosphorous reagent. This zinc removal process was installed in the plating plant and succeeded in extending the life of the strike bath by 3-5 times.