Selective recovery of rare earth elements from acetic leachate of NdFeB magnet by solvent extraction

Due to their indispensable role in a wide range of advanced technologies, rare earth elements (REEs) are becoming increasingly essential. As a result, there is a growing need to develop optimised processes for the recovery of these elements, whether from primary or secondary sources. This need extends to the recovery of REEs from a variety of sources, including mine tailings, the recycling of end-of-life products and the management of urban and industrial waste. The recovery of REEs from NdFeB permanent magnets from end-of-life computers hard disk drives (HDDs) is a great opportunity if separation from iron is effective. For this purpose N,N,N′,N′-tetraoctyldiglycolamide (TODGA) has been used for the selective extraction of REEs from a real leachate, obtained by NdFeB magnet powder dissolution in acetic acid. Process parameters such as TODGA concentration, ionic strength, time, and temperature have been investigated highlighting the complete selective recovery of REEs from the acetic acid leachate. The results show that TODGA at a concentration of 0.25 mol/L in aliphatic diluents allows the selective extraction of rare earths from an acetic acid feed solution at 1.6 mol/L, when NaNO3 is added, with high separation coefficients for REEs in regards to iron, boron and nickel respectively. After a stripping step, the recyclability of the extractant phase was also demonstrated for at least 9 cycles. The complete process allows the recovery of the REEs from the NdFeB leachate with efficiencies of approximately 92 %, 88 % and 99 % for Nd, Pr and Dy respectively.