Recovering Neodymium From Steel Mill Slag

Substantial amounts of the rare-earth element neodymium can be recovered from a previously untapped source—the waste stream from some types of steel mills, according to a report in Energy Technology (2015, DOI: 10.1002/ente.201402162). The tight supply of rare-earth minerals has made headlines in recent years because of the technological importance of these materials and export restrictions imposed upon them by China, the world’s largest supplier. Rare-earth metals are widely used to make magnets for electric motors in automobiles and other products. Commercial recycling operations recover the valuable metals from phosphors used in the lighting industry and from computer disk-drive magnets. But as H. M. Dhammika Bandara and Marion H. Emmert of Worcester Polytechnic Institute and coworkers point out, neodymium in automobile motors and household appliances, including refrigerators and air conditioners, currently is not recycled. Nor is it known in which end-of-life waste stream the metal ends up. By analyzing metal samples from shredding plants and waste from steel mills that process steel scrap, the team found that substantial amounts of neodymium (0.03% by weight) accumulate in the steel mill slag. The team did not detect other rare-earth metals in that source, suggesting that costly separation steps can be bypassed.