| Abstract: | A method of recovering nickel from spent electroless nickel-plating solutions has been investigated through the electrowinning method, following the precipitation of nickel by adding alkali and then dissolving this nickel precipitate with sulfuric acid. When sufficient caustic soda was added to a spent electroless nickel-plating solution to increase the pH to higher than 13, fine nickel particles, below 4 microns in size, along with nickel hydroxide were formed. After filtering the nickel precipitate, it was dissolved with a sulfuric acid solution of over 2 vol%, with which more than 95% of the nickel precipitate could be dissolved. For nickel recovery by electrowinning, the pH of the nickel solution required an adjustment of nearly 2.0. |
