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In an effort to help develop a sustainable domestic supply of rare earth elements and lessen US dependence on China for materials that are vital to the production of electronics, wind turbines, and many other technologies, two researchers at Worcester Polytechnic Institute (WPI) have developed a method of extracting rare earths from the drive units and motors of discarded electric and hybrid cars.
The process offers a recovery rate of more than 80%. While heat treatment is required for processing, all other steps can be performed at room temperature, thus resulting in a process designed for energy efficiency. Overall, the established process applies green chemistry principles for designing a hydrometallurgical process.
Selective dissolution enables efficient separation of steel and copper by taking advantage of the different reduction potentials of the materials in the mixture, while selective precipitation of RE salts is the key for obtaining pure RE products. —Bandara et al.
With support from WPI’s Center for Resource Recovery and Recycling (CR3), Marion Emmert, assistant professor of chemistry, chemical engineering, and mechanical engineering at WPI, and postdoctoral fellow H.M. Dhammika Bandara created the novel method for processing drive units and electric motors to separate chemically rare earth elements—specifically neodymium, dysprosium, and praseodymium—from other materials used to make the devices. The goal is to recycle in a sustainable and efficient manner rare earths that would otherwise be lost.
To test the process, the WPI researchers sliced the drive unit (which contains the electric motor and other components of the drive train) of an all-electric Chevrolet Spark (earlier post) into several pieces and then shredded the pieces.
Using a two-step chemical extraction process, they were able to separate the rare earth elements and also recover other recyclable materials, including steel chips and other useful materials from the drive units.
The research dates back to the spring of 2014, when WPI was named the lead institution on a $7.4-million, multi-university award from the UUS Army that supported the development of new metallurgical methods and new lightweight alloys to help the military build more effective and durable vehicles and systems. Part of that research explored methods for extracting rare earth elements from ores found outside of China and for recovering those elements from recycled materials.
The researchers say the technology has the potential to be an alternative source of rare earths, which could lessen the need to import these vital elements from China, which currently supplies about 97% of the rare earths used in manufacturing. Furthermore, since magnets containing rare earths are used in a wide range of technologies, including electric motors, wind turbines, and medical imaging devices, manufacturers would be able to improve the sustainability of their products by recycling these materials.
The fact that China has the majority of operable separation facilities in the world is a huge problem for the United States. Large car manufacturers are dependent on the magnets composed of these elements for car production, so it’s really critical for rare earth recovery and separation technologies to take hold here.—Marion Emmert
WPI’s Intellectual Property and Innovation department has filed a provisional patent on the recovery technology, and is beginning to market the technology in hopes of finding a licensee.
H. M. Dhammika Bandara, Kathleen D. Field and Marion H. Emmert (2015) “Rare earth recovery from end-of-life motors employing green chemistry design principles” Green Chem. doi: 10.1039/C5GC01255D
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