A shredded hard disk that has been mined for rare earth materials. Source: Oak Ridge National Labortory A shredded hard disk that has been mined for rare earth materials. Source: Oak Ridge National Labortory The U.S. Department of Energy (DOE) is working with Oak Ridge National Laboratory (ORNL) to invent a process that extracts rare earth elements from scrapped hard drive magnets and other sources.

Rare earth elements are used in advanced materials for energy, transportation, defense and communications applications. Magnets retain their properties even when the devices no longer work or carry current. Permanent magnets help computer hard drives read and write data, drive motors that move hybrid and electric cars, couple wind turbines with generators to make electricity and assist smartphones to translate electrical signals into sound.

ONRL is now working to make the process to scale in order to produce commercial batches of rare earth oxides.

“We have developed an energy-efficient, cost-effective, environmentally friendly process to recover high-value critical materials,” said Ramesh Bhave, membrane technology leader in ORNL’s chemical sciences division. “It’s an improvement over traditional processes, which require facilities with a large footprint, high capital and operating costs and a large amount of waste generated.”

How it works

The process involves dissolving magnets in nitric acid and continuously feeding the solution through a module supporting polymer membranes. The membranes feature porous hollow fibers with an extractant, creating a selective barrier that only lets rare earth elements pass through. That solution is then processed to yield rare earth oxides at purities exceeding 99.5%.

The process eliminates the iron completely--magnets are typically 70% iron--and recover only rare earth elements without co-extracting undesirable ones, meaning less waste is created, researchers said.

Researchers took magnets of varying composition for testing—from hard drives to magnetic resonance imaging machines to smartphones to hybrid cars—in order to see if the process worked across a broad spectrum of devices.

The next steps will explore if the process for separating rare earth elements can be developed for separating other in-demand elements from lithium ion batteries.

“The expected high growth of electric vehicles is going to require a tremendous amount of lithium and cobalt,” Bhave said.

The goal for the project is to recover hundreds of kilograms of rare earth oxides each month and validate, verify and certify that manufacturers could use recycled materials to make magnets equal to those made from fresh materials.

To contact the author of this article, email pbrown@globalspec.com