Recycling high-value rare earth elements from NdFeB waste can save resources, reduce industrial waste, protect the environment and bring considerable economic benefits. However, most traditional recovery method has a long process, high acid consumption, and is difficult to selectively recover high-value rare earth elements.  

In a study published in Separation and Purification Technology, the research group led by Prof. YANG Fan from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences proposed a new integrated method for recycling permanent magnet waste by betaine hydrochloride ([Hbet]Cl) solution extraction. 

The researchers first carried out leaching experiment on the basis of fully roasted magnetic clay samples, and selected [Hbet]Cl as the leaching agent.  

They found that when leaching temperature was 200 ℃, leaching time was 8 h, lixiviant [Hbet]Cl concentration was 0.2 mol/L, and solid–liquid ratio was 1:150 g/ml. They can get the optimum leaching results of 99.81% Pr, 97.05% Nd, 95.51% Gd, 56.24% Ce and 0.20% Fe, and almost all iron oxide remained in the residue.  

Compared with those for common lixiviants, the results of the proposed method showed a better leaching rate and selectivity. And the leaching sequence was in line with established chemical properties.  

Besides, the researchers revealed that the new lixiviant ([Hbet]Cl) will not reduce the extraction rate of rare earth by N, N-di-2-ethylhexyl diglycolamic acid (D2EHDGAA) extractant, and the extraction rate of D2EHDGAA for Nd in [Hbet]Cl leaching solution is significantly improved.  

This study provides a simple, convenient, green and low-cost method for permanent magnet recycling.