S.Z. Islam, D.A. Kang, B. Trusty, S. Dangwal, R. Bhave, P. Paranthaman
Oak Ridge National Laboratory,
United States
Keywords: membrane solvent extraction, rare earth elements, battery materials, mining ores, e-waste
Summary:
Recently, rare earth elements (REEs) such as neodymium (Nd), dysprosium (Dy) and praseodymium (Pr) have drawn tremendous attention due to their substantially increasing use in the form of permanent magnets for many applications including hybrid and electric vehicles, wind turbines, and a wide range of electronic devices. To address the growing demand and prevent the supply risk of REEs, we have developed an energy-efficient, and cost-effective membrane solvent extraction (MSX) process using a neutral extractant for the recovery of REEs from scrap permanent magnets. The results show that the REE recovery of >97% with a purity of >99.5 wt.% was achieved from a wide range of scrap magnet feedstocks. Furthermore, MSX showed high purity REE recovery from mining tailing feedstocks with low concentration of REEs. The majority of the REE components recovered from scrap magnets are Nd, Pr and Dy. Dy is an essential component of almost all types of permanent magnets due to their very specific properties such as high temperature tolerance and high coercivity. The separation of Dy from other REEs is of significant research and commercial interest because the presence of even a small amount of Dy in Nd/Pr oxide mixture has a significant impact on the market price as well as their applications. However, separation of heavy REE from light REE is a challenge due to their similar chemical and physical properties. We have also developed an MSX process using a cationic extractant for the recovery of Dy from mixed rare earth oxides. 100% pure Dy was obtained in 3-stages of the MSX process. In addition to REEs, MSX showed high performance in recovery of battery materials such as lithium, cobalt and nickel from end-of-life lithium-ion batteries. The results demonstrated that MSX is an economically viable, and environmentally friendly process for the recovery of critical minerals from a wide range of feedstocks. MSX technologies are licensed to industries for commercialization.