Magnetite precipitation for iron removal from nickel-rich solutions in hydrometallurgy process

In nickel hydrometallurgical operations, the removal of iron from process liquors was critical, with the method of choice commonly being crystallization (precipitation). In this paper special attention was given to the magnetite precipitate. Potential/pH diagram for Fe-H2O system was derived at 100 °C, and indicated that the iron ion may precipitate as magnetite at the lower oxidation potential. And the crystallization experiments proved that the iron ion partly precipitate as magnetite by slow oxidation at pH 2.0-2.2 and temperature 90-100 °C. The precipitates could be efficiently separated from the solutions by magnetic flocculation and separation. Further, analyses with Environmental scanning electron microscopy (ESEM) and X-ray Diffraction (XRD) provided a fundamental understanding of the magnetite precipitation process.