Separation of Nickel and Cobalt Utilizing Selective Reduction of Nickel in Acidic Aqueous Solution

Abstract

With the aim of separating nickel (Ni) from cobalt (Co) in acidic aqueous solution, selective reduction of Ni was examined. Sodium hypophosphite (NaH₂PO₂) was selected as a reductant, and reacted with aqueous solution containing 0.1 mol L⁻¹ nickel sulfate (NiSO₄·6H₂O) and 0∼0.05 mol L⁻¹ cobalt sulfate (CoSO₄·7H₂O) for 3 hours at 90°C. As a result, Ni was selectively reduced and separated from Co in the acidic region (pH = 4.8). Differences in reduction rate between Ni and Co were discussed, and the influence of impurities on the reduction of Ni was also examined by adding copper (Cu), iron (Fe), and zinc (Zn) ions to the feed solution.