Abstract
A solvometallurgical recycling route for the recovery of samarium, cobalt, copper and iron from SmCo magnets was developed. The SmCo magnets were first crushed and milled to powder size and then leached in a 2 mol L−1 hydrochloric acid solution in ethylene glycol. Afterwards, cobalt, copper and iron were extracted from the leachate with 50 wt% Aliquat 336® in toluene, which was pre-saturated with 37 wt% HCl. The non-aqueous solvent extraction system improved the extraction efficiency of cobalt. The extraction was optimized by evaluating the extraction rates, the effects of temperature, feed/solvent ratio and the hydrochloric acid concentration. Through the construction of a McCabe-Thiele diagram it was possible to calculate the number of stages required for continuous extraction. Cobalt was recovered from the loaded solvent by stripping with a 0.5 mol L−1 aqueous hydrochloric acid solution. Copper was recovered by stripping with a 5 vol% aqueous ammonia solution, whereas iron precipitated under these conditions. The solvent could be reused after regeneration, i.e. evaporation of water and ammonia and reintegration of toluene and HCl. The samarium left in the raffinate was extracted by 20 vol% Cyanex 272 in n-dodecane. Finally, samarium was recovered from the loaded Cyanex 272 by precipitation stripping with a 0.2 mol L−1 aqueous oxalic acid solution. The purity of the recovered cobalt chloride was 98.3 wt% and that of samarium oxalate was 99.4 wt%.
Highlights
SmCo permanent magnets were introduced in 1967 by Strnat and co-workers, using SmCo5 magnetic alloys [1,2]
Two equivalent solutions of leachate from, respectively, 2 mol L−1 hydrochloric acid in Ethylene glycol (EG) and 2 mol L−1 hydrochloric acid in water were stirred for 60 min at 40 °C, in each case with an equal volume, 2 mL, of Aliquat 336 50 wt% diluted in toluene
Samarium was recovered from the loaded Cyanex 272 as an oxalate salt by precipitation stripping with a 0.2 mol L−1 aqueous oxalic acid solution
Summary
SmCo permanent magnets were introduced in 1967 by Strnat and co-workers, using SmCo5 magnetic alloys [1,2]. The advantages of the two alloys can be combined in a composite structure In this case, the main phase is the Sm2Co17 phase, usually with addition of copper and iron to decrease the cobalt content and to increase the saturation magnetization [4,5]. SmCo magnets are used for high-temperature applications, such as turbomachinery and motors of high-end electric cars [8,9,10]. Another difference with NdFeB magnets is that the supply risk and price instability of SmCo magnets do not depend on the rare-earth element, Sm, but rather on the cobalt in the magnet alloy. Separation and Purification Technology 219 (2019) 281–289 process involves a combination of solvoleaching and non-aqueous solvent extraction
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
