Swiss innovators have light bulb moment

A Swiss innovation could open an exciting new chapter for recycling fluorescent lamps. Researchers at the Institute of Technology Zurich have developed a process inspired by nature to recover europium, one of the rarest of rare earth elements.

‘Rare earth metals are hardly ever recycled in Europe,’ observes Victor Mougel, who leads the research team. ‘There is an urgent need for sustainable and uncomplicated methods for separating and recovering these strategic raw materials from various sources.’

Part of the problem is that existing separation methods are based on hundreds of liquid-to-liquid extraction steps that are highly inefficient. ‘This means the recycling of europium has so far been impractical,’ says Marie Perrin, a member of Mougel’s R&D group.

‘Our study demonstrates how a simple inorganic reagent can significantly improve separation. It can obtain europium in a few simple steps and in quantities that are at least 50 times higher than was previously possible.’

Breakthrough

The key to this breakthrough are tetrathiometallates, small inorganic molecules featuring four sulphur atoms around tungsten or molybdenum. Tetrathiometallates are used as active substances against cancer and copper metabolism disorders.

For the first time, they are now also being used as ligands, ions or molecules that bind to a central metal atom for the separation of rare earth metals. Their unique ‘redox properties’ reduce europium to its unusual divalent state, simplifying separation from the other trivalent rare earths.

The Swiss lighting and lamp market is projected to reach EUR 587 million by the end of this year. While the production of fluorescent lamps was banned in 2023, legacy products remain a concern for recyclers. The country generates over 1 000 tonnes of lamp waste per year and has a network of 12 000 take-back locations. Thanks to this free service, Switzerland’s recycling rate for LEDS exceeds 50%.

Urban mine

If this source were tapped into, the lamp waste that Switzerland currently sends to landfill abroad could be recycled domestically, argues Mougel. He envisions lamp waste serving as an urban mine for europium. This would make Switzerland significantly less dependent on imports.

‘In the past, europium was mainly used as phosphor in fluorescent lamps and flat screens, which led to high market prices,’ he adds. ‘As fluorescent lamps are now gradually being phased out, demand has fallen, so that the previous recycling methods for europium are no longer economically viable.

‘More efficient separation strategies are nevertheless desirable and could help to utilise the vast quantities of cheap fluorescent lamp waste whose rare earth metal content is around 17 times higher than in natural ores.’