Q. Truong, S. Rokkam, J. Baltrusaitis
Advanced Cooling Technologies Inc,
Keywords: neodymium, dysprosium, NdFeB, citric acid, reactive grinding, NaOH
Summary:Rare Earth Elements have grown in importance over the years because of their applications in electronics, rechargeable batteries, renewables, and the defense industry. The recycling of neodymium and dysprosium contained in NdFeB magnets from the End-of-Life electronics will improve the total supply of neodymium and dysprosium in the future. However, due to the use of expensive and hazardous acids (hydrochloric or sulfuric), no mature and economically feasible technologies have been identified for recycling NdFeB magnet powders. The extraction process utilizes a two-stage process. The NdFeB powders go through wet ball mill grinding to pretreat with sodium hydroxide (NaOH) solution to form rare earth hydroxides. The rare earth hydroxides then go through leaching in mild acids. The leaching efficiencies of nitric acid, humic acid, and citric acid were investigated. As a result, a leaching efficiency of 69% for Nd and 100% for Dy was achieved after 60 minutes of milling with 3.5 mL of 4.0 M NaOH, and 60 minutes of leaching with 100 mL of 0.5 M citric acid into the solution phase. Subsequently, 100% of iron (Fe) content can be removed out of the solution. Finally, neodymium and dysprosium can be separated using multi-stage acid stripping. This work was from a SBIR program funded by The U.S. Defense Logistics Agency, Contract SP4701-19-P-0048, awarded to ACT, Inc.