Recycling rare-earth elements from lamps

Chemists from KU Leuven have utilised ionic liquid technology to recycle the metals europium and yttrium from fluorescent and energy-saving lamps. The rare-earth elements (REEs), which are typically difficult to mine, purify and source from China, can then be directly re-usable in new lamps.

Europium and yttrium are both used in red lamp phosphor, a substance which transforms ultraviolet light into red light. Professor Koen Binnemans explained that it is “very difficult to replace the red phosphor with a rare-earth-free mixture”, yet it is also technically complex to recuperate the metals from end-of-life fluorescent and energy-saving lamps using traditional solvents. The powder containing the two critical metals is therefore “typically not re-used”, Professor Binnemans said.

Chemist David Dupont said the KU Leuven team developed an alternative method, whereby instead of employing an acid as the solvent, they used an ionic liquid. The team’s study has been published in the journal Green Chemistry.

“[Ionic liquid] is an organic dissolving agent that consists entirely of ions or electrically loaded particles,” Dupont said. “It does not evaporate, it is inflammable and it works very selectively: we can design it in such a way that it only dissolves the red lamp phosphor. The recycled europium and yttrium can be directly re-used. Furthermore, the ionic liquid is also re-usable for a next cycle.”

The recycling method requires less energy and fewer chemicals, added Professor Binnemans. He said, “Both from a technical and environmental perspective, this approach is a very interesting alternative for traditional solvents.”

Source