Efficient recovery of rare earth elements from discarded NdFeB magnets

Discarded NdFeB magnets are becoming the focus of recycling rare earth metals since the content can reach as high as about 30%. In this study, a novel carbonization/hydrogenation-hydrolysis process was proposed for the recovery of rare earth elements (REEs) from discarded NdFeB magnets by using biochar derived from waste sawdust as an extracting agent. Results showed that NdFeB magnets could react with biochar to form NdFeB-C/H alloy in the carbonization/hydrogenation process. Three factors including material placement mode, temperature and NdFeB powder layer thickness affected the C/H saturation of formed NdFeB-C/H alloy in this process. When NdFeB powder layer with thickness of lmm was placed above biochar layer (Mode-3) and carbonized/hydrogenated for 90 min at 1400 degrees C, the C/H saturated NdFeB-C/H alloy subsequently generated 99.43% of rare earth hydroxides purity and 88.4% of the REEs recovery efficiency after hydrolysis and magnetic separation process. All findings indicated that the new carbonization/hydrogenation-hydrolysis process using biochar as an extractant could be an efficient approach for recovering REEs from discarded NdFeB magnets. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.