NdFeB magnet scrap valorization by leaching and recovery of rare earth metals by sorption on low-cost expanded clay

Abstract

The search for new sources of rare earth metals (REM), such as neodymium and dysprosium, has ensued globally due to their strategic value for the sustainability of the energy sector. In this context, this work explored the potential of vermiculite as a sorbent for recovering rare earth cations from the leachate of end-of-life NdFeB magnets by kinetic, equilibrium, and desorption investigations. In which the REM uptake on vermiculite occurred by fast kinetics, and the significant sorbate-sorbate interactions at the equilibrium indicated that the REM sorption was a cooperative process; vermiculite sorbed the metals from the acid leachate in the following order: Fe(III) > Nd(III) > Zn(II) > Pr(III) > Co(II) > Dy(III) > Ni(II) > Al(III) > Mn(II); and the chelating agent ethylenediaminetetraacetic acid desorbed Nd(III) preferably over other metals, indicating the potential for further selective recovery processes. The characterization analyses indicated that the loaded vermiculite preserved the original structure, composition, functional groups, and thermal stability. Also, X-ray photoelectron spectroscopy corroborated the cation exchange mechanism between interlayer magnesium in the REM sorption. Thus, the experimental findings and a cost analysis compared to the literature demonstrated the cost-effectiveness and potential of vermiculite for the valorization of NdFeB magnet leachates.