New process pulls europium from e-waste

Rare earth elements (REEs) are essential building blocks for the world's electronics and a host of developing energy transition technologies. Found in smartphones, computers, screens, and batteries, they are essential in everything from smartwatches to wind turbines.

This suite of 15 elements, however, are notoriously challenging to separate. Conventional processes are often chemical-heavy and energy-intensive, requiring multiple extraction and purification steps, which are slow, expensive, resource-heavy and often environmentally harmful.

"Rare earth metals are hardly ever recycled in Europe," said Victor Mougel, professor at the Laboratory of Inorganic Chemistry at ETH Zurich and leader of a team of researchers determined to break convention and dig into the bounty of e-waste to recapture these critical minerals.

"There is an urgent need for sustainable and uncomplicated methods for separating and recovering these strategic raw materials from various sources," says Mougel.

Published in Nature Communications, the team presents a nature-inspired method for efficiently separating and recovering the rare earth metal europium from complex mixtures, including other rare earth metals.

Nature Communications (2024)

Illustrated circular process for europium recovery from a spent compact fluorescent bulb according to the process described in the publication.

Learning from nature

"Existing separation methods are based on hundreds of liquid-liquid extraction steps and are inefficient – the recycling of europium has so far been impractical," said Marie Perrin, a doctoral student and first author of the study.

The study demonstrates how a simple inorganic reagent (molecules featuring four sulfur atoms around tungsten or molybdenum) can significantly improve separation.

"This allows us to obtain europium in a few simple steps-and in quantities that are at least 50 times higher than with previous separation methods," said Perrin.

The researchers were inspired by proteins that use these molecules as a binding site for metals in natural enzymes and are utilized in medicine as treatments for cancer and copper metabolism disorders.

They are now also being used in the separation of rare earth metals. Their unique redox properties alter the europium to a distinctive state, simplifying separation from the other rare earths.

"The principle is so efficient and robust that we can apply it directly to used fluorescent lamps without the usual pre-treatment steps," says Mougel.

Old waste, new strategies

Electronic waste is a highly underutilized source of rare earth metals.

"If this source were tapped into, the lamp waste that Switzerland currently sends abroad to be disposed of in a landfill could be recycled here in Switzerland instead," said Mougels.

In the past, europium was mainly used in fluorescent lamps and flat screens, whose REE content is around 17 times higher than in natural ores. As fluorescent lamps are now being phased out for more eco-friendly LED designs, demand has fallen, leaving previous recycling methods for europium less viable.

With a new demand for europium, modernized recycling strategies are required to recover the material from the vast quantities of cheap fluorescent lamp waste that are still hiding a wealth of REEs.

In principle, any separation process for rare earth metals can be used both for extraction from ore and for recovery from waste. However, with the value of REEs in e-waste so much higher than raw ore, the researchers are focused on recycling, as this makes much more ecological and economic sense.

"Our recycling approach is significantly more environmentally friendly than all conventional methods for extracting rare earth metals from mineral ores," says Mougel.

The researchers have patented their technology and are in the process of founding a start-up called REEcover to commercialize it in the future. They are currently working on adapting the separation process for other rare earth metals, such as neodymium and dysprosium, found in permanent magnets and used in everyday electronics from computers and appliances to MRI machines and wind turbines.

Perrin intends to pursue the start-up upon completing her doctorate and establish commercial REE recycling to help lower emissions, bolster domestic supply and reduce foreign dependency.