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The growing demand for rare earthRare earths elements (REEs)Rare earth elements in advanced technologies, combined with supply shortages, presents an opportunity for resource recoveryRecovery from secondary sources. Permanent magnets (NdFeB)NdFeB are widely used, with their high RE content (~25–32%) can serve as a valuable secondary REE source. This study utilizes copper-basedCopper salts (chloride/nitrate/sulphate) to dissolve rare earths selectively and eliminates the use of corrosive acids. The leachingLeaching behaviour of NdFeB varies with different copper salts; co-dissolution of iron was observed for copper chloride lixiviant due to stable chloro-complexes formation compared to nitrate-complexes, whereas copperCopper sulphate displayed slower dissolution kinetics. This study employs copper nitrateCopper Nitrate (Cu(NO3)2.3H2O) assisted leaching, followed by oxalic acid precipitationPrecipitation, and calcination to produce high-purity mixed RE oxides (~98–99%). During Cu-nitrate leachingLeaching, redox displacement (of Fe/Nd) due to Cu2+ ions takes place, and nitrate ions oxidize rare earthsRare earths further to soluble REE3+ under acidic oxidative conditions. At the same time, Fe2/3+ hydrolyses ultimately lead to leached residue. The process is optimized by varying the temperature (30–90 °C), Cu(NO3)2.3H2O to NdFeBNdFeB dosage (0.75:1–2:1), duration (0.5–5 h), and S/L (20–50) to enhance REERare earth elements dissolution. The REE (Nd + Dy + Pr) extractionExtraction was ~92.6% at optimum conditions of 1.75:1 dosage (Cu(NO3)2.3H2O: NdFeB), 50 °C, 5 h, and S/L of 20.

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Acid-Free Leaching Studies of Spent HDD Magnets for Recovery of Rare Earth Values

  • 会议论文

  • 发表日期：

    2026年

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  • Rohit Gahlot

摘要

The growing demand for rare earthRare earths elements (REEs)Rare earth elements in advanced technologies, combined with supply shortages, presents an opportunity for resource recoveryRecovery from secondary sources. Permanent magnets (NdFeB)NdFeB are widely used, with their high RE content (~25–32%) can serve as a valuable secondary REE source. This study utilizes copper-basedCopper salts (chloride/nitrate/sulphate) to dissolve rare earths selectively and eliminates the use of corrosive acids. The leachingLeaching behaviour of NdFeB varies with different copper salts; co-dissolution of iron was observed for copper chloride lixiviant due to stable chloro-complexes formation compared to nitrate-complexes, whereas copperCopper sulphate displayed slower dissolution kinetics. This study employs copper nitrateCopper Nitrate (Cu(NO3)2.3H2O) assisted leaching, followed by oxalic acid precipitationPrecipitation, and calcination to produce high-purity mixed RE oxides (~98–99%). During Cu-nitrate leachingLeaching, redox displacement (of Fe/Nd) due to Cu2+ ions takes place, and nitrate ions oxidize rare earthsRare earths further to soluble REE3+ under acidic oxidative conditions. At the same time, Fe2/3+ hydrolyses ultimately lead to leached residue. The process is optimized by varying the temperature (30–90 °C), Cu(NO3)2.3H2O to NdFeBNdFeB dosage (0.75:1–2:1), duration (0.5–5 h), and S/L (20–50) to enhance REERare earth elements dissolution. The REE (Nd + Dy + Pr) extractionExtraction was ~92.6% at optimum conditions of 1.75:1 dosage (Cu(NO3)2.3H2O: NdFeB), 50 °C, 5 h, and S/L of 20.