Process Flowsheet Development for Separation of Sm, Co, Cu, and Fe from Magnet Scrap

Area of Science:

• Metallurgical Engineering
• Materials Science
• Hydrometallurgy

Background:

• Sm₂Co₁₇ magnets are critical in various high-tech applications.
• Efficient recovery of valuable metals from spent magnets is crucial for resource sustainability.
• Existing recycling processes often face challenges in selectively separating rare earth elements and transition metals.

Purpose of the Study:

• To develop and optimize a complete process flowsheet for recovering metal values from Sm₂Co₁₇ magnet scrap.
• To investigate selective separation techniques for samarium (Sm) and cobalt (Co).
• To evaluate the efficiency of solvent extraction for copper (Cu) and cobalt recovery.

Main Methods:

• Leaching of magnet scrap in a chloride medium using hydrochloric acid (HCl) and hydrogen peroxide (H₂O₂).
• Optimization of leaching conditions using a full factorial Design of Experiment.
• Selective precipitation of Sm as a double sulfate salt, followed by conversion to Sm-oxalate and calcination to Sm₂O₃.
• Iron (Fe) removal via pH adjustment.
• Solvent extraction using LIX 84I for Cu and Na-CYANEX 272 for Co recovery.

Main Results:

• Optimized leaching achieved 98.5% Sm and 99% Co extraction.
• Selective precipitation successfully isolated Sm₂O₃.
• Efficient removal of Fe was demonstrated by raising the pH to 3.0.
• Solvent extraction provided effective recovery pathways for Cu and Co, with McCabe-Thiele diagrams presented.

Conclusions:

• A viable and efficient process flowsheet for Sm₂Co₁₇ magnet scrap recycling has been established.
• The developed method allows for high-yield recovery of valuable metals, particularly Sm and Co.
• The study provides a foundation for industrial-scale recycling of rare earth magnets.