Process Scale-Up of an Energy-Efficient Membrane Solvent Extraction Process for Rare Earth Recycling from Electronic Wastes

Abstract

This study reports the process scale-up and long-term performance of an energy-efficient and cost-effective membrane solvent extraction (MSX) process for separation and recovery of high purity rare earth oxides (REOs) from scrap permanent magnets (SPMs). The rare earth elements (REEs), including dysprosium, neodymium, and praseodymium, are recovered from SPMs using a neutral extractant, tetraoctyl diglycolamide (TODGA) embedded in a microporous polypropylene hollow fiber membrane module. The MSX process performance is demonstrated with bench scale module with membrane surface area of 1.4 m2 to industrial scale modules with membrane surface area of up to 20 m2 to enable the processing of up to 1 ton month−1 of SPMs. The purity and the yield of the recovered REOs are >99.5 wt% and >95%, respectively. The average extraction rate of REOs is >10 g m−2 hr−1. A skid of MSX system is assembled with a membrane area of 40 m2. The MSX skid successfully recovers REOs with a capacity of 300 kg REOs/month. Finally, it is determined that the organic phase containing the extractant maintains its performance up to 250 h. The results suggest that the MSX process is an economically viable and environmentally friendly process for separation and recovery of REOs from electronic wastes.