Thermal Isolation of Rare Earth Oxides from Nd–Fe–B Magnets Using Carbon from Waste Tyres

摘要

src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ascecg/2017/ascecg.2017.5.issue-7/acssuschemeng.7b01133/20170627/images/medium/sc-2017-01133k_0007.gif">In this study, a novel oxidation–reduction process for the recovery of rare earth elements (REEs; i.e., Nd, Pr, and Dy) from Nd–Fe–B permanent magnets is verified. Nd–Fe–B permanent magnets collected from e-waste were subjected to an oxidation process at 1000 °C for 60 min followed by carbothermal reduction at 1450 °C for 90 min using waste tire rubber-derived carbon (WTR-DC) as a reducing agent. Fe-based metal and rare earth oxide (REO) phases were successfully separated from the original magnets. The distribution of elements (i.e., Nd, Dy, Pr, Fe, B, Al, and C) between the Fe-based metal and oxide phases was investigated via Inductively Coupled Plasma (ICP) and Energy-Dispersive X-ray Spectroscopy EDS/Electron Probe Microanalysis (EPMA) elemental mapping. REEs were confirmed as the main components of the oxide phase, and it was shown that the REEs did not remain in the Fe-based metal phase. Given the growing global demand for REEs, critical supply issues, high costs, and extremely low recycling rates worldwide, new recycling options are urgently needed. This new approach to extracting REEs from Nd–Fe–B magnets, using a problematic waste (WTR) as a reductant, promises to simultaneously deliver environmental benefits.