College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, People's Republic of China.
Institute of Zhejiang University-Quzhou, 78 Jiuhua Boulevard North, Quzhou, Zhejiang 324000, People's Republic of China.
Environ Sci Technol. 2020 Aug 18;54(16):10370-10379. doi: 10.1021/acs.est.0c03278. Epub 2020 Jul 30.
The NdFeB permanent magnet is a critical material in digital electronics and clean energy industry. Traditional recovery processes based on the solvent extraction technique would consume high energy and large amounts of chemicals as well as resulting in abundant secondary organic wastes. In this work, a green process using deep eutectic solvents (DESs) in the selective leaching technology was designed to recover NdFeB permanent magnets. Nine kinds of DESs composed of guanidine were prepared and screened as the leachants. The guanidine hydrochloride-lactic acid (GUC-LAC) combined DES achieved the highest separation factor (>1300) between neodymium and iron through simple dissolution of their corresponding oxide mixture. The mass concentration of Nd dissolved in the GUC-LAC DES could reach 6.7 × 10 ppm. The viscosity of this type of DES at 50 °C was 36 cP, which was comparable to many common organic solvents. In a practical recovery of roasted magnet powders, the NdO product with 99% purity was facilely obtained with only one dissolution step, followed by a stripping process with oxalic acid. Even after 3 cycles, the GUC-LAC DES kept the same dissolution property and chemical stability. With such superior performances in selective leaching of rare earth elements from transition metals, the GUC-LAC DES is greatly promising in the rare earth element recovery field.
钕铁硼永磁体是数字电子和清洁能源产业的关键材料。传统的基于溶剂萃取技术的回收工艺会消耗大量的能源和化学品，同时还会产生大量的有机二次废物。在这项工作中，设计了一种使用深共熔溶剂（DESs）的绿色工艺，用于选择性浸出技术中回收钕铁硼永磁体。制备了 9 种由胍组成的 DESs，并将其作为浸出剂进行筛选。通过简单地溶解相应的氧化物混合物，胍盐酸-乳酸（GUC-LAC）复合 DES 实现了钕和铁之间的最高分离因子（>1300）。GUC-LAC DES 中溶解的 Nd 的质量浓度可达 6.7×10 ppm。在 50°C 下，这种类型的 DES 的粘度为 36 cP，与许多常见的有机溶剂相当。在实际回收焙烧磁粉的过程中，仅通过一步溶解，然后用草酸进行脱除，就可以得到纯度为 99%的 NdO 产品。即使经过 3 次循环，GUC-LAC DES 仍保持相同的溶解性能和化学稳定性。由于 GUC-LAC DES 在从过渡金属中选择性浸出稀土元素方面具有如此优异的性能，因此在稀土元素回收领域具有广阔的应用前景。
