Development of Hydrometallurgical Process for Recovery of Rare Earth Metals (Nd, Pr, and Dy) from Nd-Fe-B Magnets
Development of Hydrometallurgical Process for Recovery of Rare Earth Metals (Nd, Pr, and Dy) from Nd-Fe-B Magnets
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DOI：
10.3390/met11121987
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发表时间：
2021-12-01
期刊：
影响因子：
2.9
通讯作者：
Jha, Manis Kumar
中科院分区：
文献类型：
--
作者：
Choubey, Pankaj Kumar;Singh, Nityanand;Jha, Manis Kumar
稀土金属（REMs）丰富的初级资源的不可用性和含有REMs的大量废弃磁铁的产生，迫使研究人员探索从废弃磁铁中回收REMs的可能性。因此，本文报道了从废弃的Nd-Fe-B磁体中回收稀土元素（Nd、Pr和Dy）。该工艺包括退磁、预处理和湿法冶金处理，以回收稀土元素作为盐。浸出研究表明，在优化的实验条件下，95.5%的Nd、99.9%的Pr和99.9%的Dy被溶解，酸浓度2 M H2SO 4，温度75 ℃，纸浆密度100 g/L，和混合时间60 min。尝试溶剂萃取技术用于选择性萃取/分离REM和Fe。结果表明，99.1%（24.42 g/L）的Nd沿着与90%（1.08 g/L）的Pr和总Fe在有机/水（O/A）比为1/1，eq.在10分钟的混合时间内pH 3.5。它需要多级分离，因此从经济角度来看是不可行的。因此，REMs盐和氧化铁作为颜料的直接沉淀进行了研究，使用两个阶段的沉淀在不同的pH值。得到的REMs和Fe的氢氧化物的沉淀分别干燥，以除去水分，并在高温下进一步处理，得到纯REMs氧化物和红色氧化物。
Non-availability of rich primary resources of rare earth metals (REMs) and the generation of huge amounts of discarded magnets containing REMs, compelled the researchers to explore the possibilities for the recovery of REMs from discarded magnets. Therefore, the present paper reports the recovery of REMs (Nd, Pr, and Dy) from discarded Nd-Fe-B magnets. The process consists of demagnetization, pre-treatment, and hydrometallurgical processing to recover REMs as salt. Leaching studies indicate that 95.5% Nd, 99.9% Pr, and 99.9% Dy were found to be dissolved at the optimized experimental condition i.e., acid concentration 2 M H2SO4, temperature 75 degrees C, pulp density 100 g/L, and mixing time 60 min. Solvent extraction technique was tried for the selective extraction/separation of REMs and Fe. The result indicates that 99.1% (24.42 g/L) of Nd along with 90% (1.08 g/L) of Pr and total Fe were co-extracted using 35% Cyanex 272 at organic to aqueous (O/A) ratio 1/1, eq. pH 3.5 in 10 min of mixing time. It requires multistage separation and therefore, not feasible in view of economics. Thus, direct precipitation of REMs salt and iron oxide as pigment was studied using two stages of precipitation at different pH. The obtained precipitate of REMs and Fe hydroxides were dried separately to remove the moisture and further treated at elevated temperature to get pure REMs oxide and red oxide.