Magnetic separation of iron precipitate from nickel sulfate solution by magnetic seeding

• The pH value influenced the nickel loss and the filterability.
• The lower pH guaranteed nickel recovery at the cost of filterability.
• The magnetic seed contributes to the iron precipitation.
• The residues were large particles with core-shell structures.
• Magnetic separation offseted the poor filterability of the precipitate.

The application and development of goethite process were hindered by the poor filterability of the precipitate and the great loss of nickel in nickel hydrometallurgy. In this study, the effects of pH on the goethite precipitation and the mechanism of the nickel loss were investigated. The goethite precipitation at a lower pH (2.4 to 3.0) guaranteed a higher recovery of nickel at the cost of the filterability of the precipitate. Then a novel process, magnetic seeding and separation, was proposed to improve the filterability of iron residues and simplify the iron removal process. The iron precipitated on the surface of the magnetic seeds to form a large particle with core-shell structures and the magnetic core endowed the particles magnetism. Efficient magnetic separation offseted the poor settleability and filterability of the precipitate. After magnetic separation of iron residue, the nickel solution was qualified and the dried iron residue contained more than 52% Fe and less than 0.6% Ni, indicating a promising alternative process for treatment of bulky residues of iron precipitate. Further analyses with Environmental scanning electron microscopy (ESEM) and X-ray Diffraction (XRD) provided a fundamental understanding of the new process.

The iron precipitated or aggregated on the surface of the magnetic seeds as goethite, forming big particles with core-shell structures. The magnetic core endowed the particle magnetism and the magnetic particles aggregated together by the magnetic force in magnetic field.Figure optionsDownload as PowerPoint slide