Selective leaching and recovery of rare earth from NdFeB waste through a superior selective and stable deep eutectic solvent

The recovery of rare earth elements (REEs) from NdFeB waste is crucial for advanced industrial development. The green and superior selective recovery methods can effectively avoid the problem of generating large amounts of wastewater and high pollution in the NdFeB waste recycling process. In this work, a novel deep eutectic solvent (DES) synthesized by tetraethylammonium chloride (TEAC) and levulinic acid (LA) was designed and achieved selective leaching of REEs from NdFeB waste without wastewater produced. The leaching ratio of Nd can reach up to 97.63 %, while Fe is less than 0.435 %, the separation factor can exceed 9000, and the purity of the obtained product Nd2O3 is 99.649 %. In addition, the solubility of Nd2O3 in TEAC-LA is over 75.6 g/L, the thermal stability temperature reaches 132.4 °C much higher than the working temperature, and the viscosity is 12.8 cP at the working temperature which is close to prevalent organic solvents. After three cycles, TEAC-LA still maintains its original selective leaching ability and shows excellent thermal stability. This study provides a superior selective and stable method for green and efficient recycling of NdFeB waste.