Removal of metallic coatings from rare-earth permanent magnets by solutions of bromine in organic solvents

Abstract

Rare-earth permanent magnets were treated with Br2 in organic solvents to remove the Ni–Cu–Ni coating prior to direct magnet recycling by hydrogen decrepitation.

A toolbox for improved recycling of critical metals and materials in low-carbon technologies

“…Preventing fluorinated polymers (like polyvinylidene fluoride (PVDF) or Nafion ® ) degradation during the recycling process is important for LiBs, 62 fuel cells and the backsheet films of photovoltaic modules. Magnets are encased in organic binders 63 or coated with other metals 64 to prevent corrosion (which is particularly important for offshore wind turbine magnets); removal and separation of this coating is necessary. Solar cells can easily be crushed and sieved, which allows recovery of glass fractions 65 efficiently and separating out polymer-rich (>5 mm) and metal-rich fragments (<0.25 mm) according to particle size.…”

Chromatographic separation of rare earths from aqueous and ethanolic leachates of NdFeB and SmCo magnets by a supported ionic liquid phase

“…However, the solvation of the formed species only partly explains the observed differences, as the particular property of the solvent or a solution cannot serve as the sole parameter determining the leaching efficiency of the magnet. 12 …”

Oxidative Dissolution of Metals in Organic Solvents

“…Recently, bromine in organic solvents has shown potential for removal of the metallic nickel–copper–nickel protective coatings of rare-earth permanent magnets (Nd–Fe–B and Sm–Co magnets), prior to recycling of the rare-earth elements. 34 Among five solvents tested, namely 1 vol % of bromine in EtOH, DMF, EG, EtOAc, and MeOAc, the first two solutions could selectively dissolve nickel and copper without leaching the magnet alloy ( Figure 3 ). Dissolution of metals in Br 2 -EG was slow due to the high viscosity of EG which is 1 order of magnitude higher than that of ethanol or DMF.…”

“…The recovery yields, η (%), were the ratio of the concentration of a metal in solution after leaching for 20 min to the concentration of the same metal if all the content of the coating would be dissolved in solution. Reprinted from ref ( 34 ). Copyright 2019 Royal Society of Chemistry under [CC BY-NC 3.0] [ ].…”