A new recycling process recovers valuable rare earth elements from scrap metal, minimizing the need for harmful mining operations.
As the use of electronics grows and mankind’s dependence on technology grows, the need for rare earth elements that are an integral part of these devices is also rapidly increasing. For example, the demand for a heavy rare earth element – dysprosium – is expected to increase by 2600% over the next two decades.
While rare earth elements, also called rare earth metals, are abundant in the earth’s crust, extracting them is far from straightforward, requiring complex mining and processing operations to separate them from the minerals that contain them. These mining operations can release toxic chemicals into the environment, and the leach ponds needed to extract rare earth elements can themselves “leak” into groundwater.
An increased need for these materials is therefore accompanied by increased environmental risks.
Recycling of rare earth elements
One possible avenue to mitigate this demand and the accompanying risk to the environment is to ensure that these materials can be efficiently extracted from e-waste. This means developing an extraction process that is economically viable and scalable, something that currently does not exist, which means valuable resources linger on the literal scrap heap.
Research published in the journal Advanced Engineering Materials demonstrates the performance of an energy efficient extraction process to separate and recover high purity rare earth oxides – a useful subsection of rare earth elements bound to oxygen molecules – from magnets permanently contained in discarded electronic devices, which were essential to the operation of the device during its lifetime.
The membrane designed by Ramesh Bhave, a team leader at Oak Ridge National Laboratory, and his team is made from a plastic called polyprolene and filled with tiny porous holes called micropores that help filter out rare-earth elements. The membrane is then enclosed in an individual module.
Its modular design and the fact that it is a one-step process makes the rare earth element extraction technique developed by the team cost-effective and scalable for use in industry, which means that it could dramatically increase the availability of rare earth elements for electronics.
The team says the process they’ve developed can be made environmentally friendly, while allowing for the use of e-waste.
“Rare earth elements have attracted urgent attention around the world and have become strategically critical to the security of the global economy, energy, transportation and communications,” Bhave said. “This is due to their increasing use in various advanced technologies, including hybrid and electric vehicles, wind turbines, mobiles, tablets, personal computers, a wide range of electric motor devices and many other technological innovations. “
Use of electronic waste
Currently, when electronic devices are thrown away, the permanent magnets they contain end up in landfills and remain there along with their valuable rare earth elements that are wasted.
“According to the recent Electronics Take Back Coalition report, approximately 31 million computers and 135 million mobile devices were discarded in 2010 as electronic waste,” Bhave said. “The average annual sales of computers, tablets, and mobile devices in the United States between 2013 and 2015 were 63, 83, and 154 million units, respectively, which likely contributed to a huge amount of e-waste. This corresponds to approximately 1,630 tonnes of potentially recyclable magnets from consumer electronics alone.
The extraction method tested by Bhave and his colleagues had been developed and refined in previous work published by the team, but this current study aimed to demonstrate the scalability, flexibility and efficiency of the process by testing it at more large scale.
Since scrap magnets are demagnetized – to avoid the risk of fire – and are then shredded, a successful rare earth oxide extraction process must separate these materials from non-rare earth elements, such as iron , aluminum, copper and zinc.
The purity of the recovered rare earth element obtained using this extraction method was up to 99% by weight with a yield as high as 95%. The extraction rate was greater than 10 grams of rare earth oxides per square meter of raw magnetic material per hour.
By adapting the modules to an industrial-scale application, Bhave and his team discovered that the process of the rare earth element extraction method can produce 300 kilograms per month of rare earth oxides from one ton of raw material of permanent magnets.
Future efforts
The promising results are a decade in the making. “We initiated the Rare Earth Elements Separation and Recovery Program approximately 10 years ago to fulfill the U.S. Department of Energy’s mission to ensure the nation’s supply of critical materials, including the elements of rare earths,” Bhave explained. “This is the first comprehensive report on the recovery of rare earth oxides from permanent magnet scrap at the pilot scale of the rare earth element extraction method system.”
The team will now continue their efforts to scale up the process they have developed and start demonstrating it “in the field” to see how it works in real world conditions where it will need to be used if commercialized rather than in a more controlled environment. laboratory setting.
In addition to this, Bhave pointed out that the process of extracting rare earth elements is improved and made self-sufficient by the development of a technique for treating waste water used in the process. This allows water to be recovered and reused.
Because the solution used to extract the rare earth elements leaves iron and other non-rare earth elements in the wastewater, the team developed a method to recover iron oxide from the wastewater after removal. rare earth elements.
“Recovering all non-rare earth elements and reusing the reclaimed water in the process essentially makes it a near-zero discharge process and supports a closed-loop circular economy,” Bhave added.
“These results suggest that the rare earth element extraction process is an economically viable and environmentally friendly process for the separation and recovery of rare earth oxides from electronic waste,” the team concluded in his article.
Reference: Syed Z Islam, et al, Scaling up an Energy Efficient Membrane Solvent Extraction Process for Recycling Rare Earths from E-Waste, Advanced Functional Materials (2022). DOI: 10.1002/adem.202200390
Image credit: Shutterstock/Ulrich Mueller
