Ni Cementation Followed by Magnetic Separation for Recovery of Unreacted Zn from by-products of Zn Smelting Process

A purification process using cementation to remove Co ions in the course of Zn metallurgy process generated precipitate containing Cu, Sb, Zn as well as Co. Because an excess amount of Zn is generally added to the cementation process to guarantee the Co removal, this study used a magnetic separation process to recover unreacted Zn powder. Nickel was added to simulated Zn leach solution ([Zn]=150 g/L, [Co]=[Sb]=10 mg/L, [Cu]=200 mg/L) and the precipitate with Ni component was generated by adding Zn powder to the solution. When the concentration of Ni was 120 mg/L, no magnetic separation of the precipitates was observed. In contrast, after the concentration of Ni increased to 240 mg/L, when the cementation test was performed for 30 minutes at 85°C and pH 3.3-3.7, and then precipitates were separated with a magnet, 53.4% Ni, 56.7% Cu, 48.2% Co, 57.0% Sb, and 11.9% Zn were recovered in the magnetic fraction, whereas 88.1% Zn was concentrated in the non-magnetic fraction.