Development of Electrochemical Dissolution Method for Nickel Sulfide-Metal Alloy with Cathodic Nickel-Copper Precipitate Formation

A method is developed for separating nickel-copper alloy by electrolysis of crushed nickel matte in sulfuric acid solution to obtain a cathode precipitate, an electrolyte solution saturated with nickel, and sulfur-sulfide sludge. A distinctive feature of this work is use of a bulk anode formed by crushed matte particles with a size of 0.5–5 mm. Nickel matte is formed by nickel phase Ni₃S₂ and precipitates of Ni–Ni₃S₂ eutectic 10–40 μm in size. Nickel metal also occurs at particle boundaries in the form of localized inclusions. The possibility of conducting anodic dissolution of crushed nickel matte in the form of a bulk anode and cathodic reduction of compact nickel-copper deposit in one electrolysis bath is confirmed by experiment. It is found that dissolution of metallized phase occurs most intensively from a particle surface. Electrolysis regimes are determined. With a sulfuric acid concentration in the electrolyte of 10 g/dm³, a bath voltage of 2.2–2.5 V, and an anode current density of 25 A/m², anodic current efficiency of 87% is achieved. As a result of electrolysis of nickel matte with the parameters selected a compact nickel-copper deposit with a nickel content of more than 90% may be obtained on the cathode.