A Multi-stage Process for Recovery of Neodymium (Nd) and Dysprosium (Dy) from Spent Hard Disc Drives (HDDs)

ABSTRACT

Waste electrical and electronic equipments (WEEE or e-waste) are an important source for rare earth elements (REEs). Among various type of WEEE, NdFeB magnets are known for their high content of neodymium (Nd) and dysprosium (Dy). Recovery of REEs from NdFeB magnets is of prime interest for the industry to meet the ever-growing demand for REEs. In this study, some physical and hydrometallurgical approaches including demagnetization, grinding, screening, leaching, precipitation and extraction have been adopted to study the Nd and Dy recovery from spent NdFeB magnets. Various inorganic (HCl, HNO₃, H₂SO₄ and aqua regia) and organic reagents (acetic acid and oxalic acid) were tested as lixiviants for leaching of the magnets. As a new approach, the recovery of Nd and Dy in the leaching solution was tested by eliminating the iron by a solution purification process involving precipitation of ferric iron in solution as hydroxide and solvent extraction with ionic liquids (ILs). The comparative studies demonstrated that the extraction efficiency of di-2-ethylhexyl phosphoric acid (D2EHPA) was higher than trihexyltetradecylphosphonium chloride (CYPHOS® IL101) after leaching stage. Nd and Dy were successfully extracted with complete recovery from the optimized system.

KEYWORDS:

• Hydrometallurgy
• ionic liquids
• NdFeB magnets
• neodymium
• dysprosium

Acknowledgments

We thank to EXITCOM Recycling for kindly providing the spent hard disks used in the experimental studies. At the same time, we would like to thank Dr. Sandeep Panda for his suggestions and different points of view.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the TUBITAK under Grant [Project No: 113Y011]; Suleyman Demirel University under Grant [Project No: 4957-D2-17].