Acetic acid leaching of neodymium magnets and iron separation by simple oxidative precipitation

Selective neodymium recovery from model permanent magnets using cost-effective organic acid systems

“…The current concentration of the acetic acid–water (6 : 1) (16.5 M) mixture studied in this work is higher than both the stoichiometry ratio of acid to metal oxide (6 mol CH 3 COOH per 1 mol Nd 2 O 3 , Nd 2 O 3 + 6CH 3 COOH = 2Nd(CH 3 COO) 3 + 3H 2 O) and the concentration of acetic acid solutions used in previous studies 10,33,34,46–50 which are in the range 0.4–3.0 M. Fig. 6 shows the Nd leaching efficiencies reported in the previous studies from the literature that used acetic acid for dissolving Nd from NdFeB magnets and metal oxides in different leaching conditions.…”

“…Previous studies attained Nd dissolution efficiencies ranging from 99.99% to 50% in acetic acid solutions by varying the concentration from 3.0 to 0.4 M. Interestingly, by using low concentrations of acetic acid (0.4–1.6 M) higher Nd solubilities (>90.0%) 10,33,34,46–49 were achieved (Fig. 6), whereas the lower Nd efficiency (50%) was achieved when using the higher concentration of acetic acid (3 M).…”

“…Nd 2 O 3 and Fe 2 O 3 are the main components in spent magnets after demagnetisation, calcination, and alkaline baking, as reported in the literature, 10,31 so it is crucial to understand their distinct dissolution properties in the mixtures of HBA–HBD. Therefore, a series of HBA–HBDs composed of guanidine hydrochloride (GUC), as a hydrogen bond acceptor (HBA) and lactic acid or acetic acid as hydrogen bond donors (HBDs) were prepared (Table 1).…”

“…[6][7][8] It is estimated that the demand for REEs will increase 40-fold from 2015 to 2030 just to meet the need for magnets in wind turbines. 9,10 Therefore, there is a need to recycle the vast amount of waste magnets to avert a REE supply crisis.…”

Phase Relations in the CaO-Nd2O3-Al2O3 System in Application for Rare Earth Recycling

“…29 Though hydrometallurgical methods allow to achieve high recovery of REEs, the disadvantage of this process is multiple steps to enhance leaching selectivity, consumption of large amounts of chemicals, compromised precipitate purity due to the presence of iron in solution and rapid (undesired) evolution of hydrogen. 29,30 In pyrometallurgical processes, e.g. during oxidative treatment, rare earth elements with a high affinity for oxygen are concentrated in the slag, while elements with a lower affinity for oxygen (predominantly iron) form a metallic liquid.…”