posted on 2024-01-30, 13:09authored byHyung-Seok Lim, Chinmayee V. Subban, Dan Thien Nguyen, Tasya S. Nasoetion, Tingkun Liu, Kee Sung Han, Bhuvaneswari M. Sivakumar, Teresa Lemmon, Soowhan Kim, Zhaoxin Yu, Arun Devaraj, Mark J. Willey, Wei Wang, Vijayakumar Murugesan
Recovering
rare earth elements (REE) from used permanent magnets,
which contain about 30 wt % of rare earth elements, has long been
a technological challenge. Current recycling methods rely on energy-
and chemical-intensive pyrometallurgical or hydrometallurgical processes
that are neither economically nor environmentally viable for rare
earth-containing magnets. Enabling an efficient and simplified process
for recovery and refining of REEs contained in end-of-use (EoU) products,
such as neodymium–iron–boron (Nd–Fe–B)-based
magnets, will significantly contribute to the future supply of these
elements. To address this, we developed a room temperature, single-step
electrochemical process that effectively separates and electroplates
REEs from commercial Nd–Fe–B magnets simultaneously.
Our approach utilizes selective oxidation and reductive potential
as electrochemical control parameters, combined with an electrochemically
compatible nonaqueous electrolyte system. This enables selective electroleaching
of lanthanides (Nd and Pr) from the magnet, serving as the anode,
and concurrent plating of lanthanides as an alloy at the Pt cathode.
The morphological and chemical evolution of the Nd–Fe–B
magnets during the electroleaching process reveals that the electrochemical
stimuli and rate of dissolution depend on the microstructural complexities
of the Nd–Fe–B magnet. The simultaneous electroplating
process leads to a Nd–Pr-based alloy, which can be used as
a raw metallic alloy for manufacturing new permanent magnets and other
devices. Our study demonstrates a scalable separation and refining
methodology, eliminating the need for consumptive chemical use and
allowing for the selective recovery of lanthanides from waste magnets.