Using eggshell waste to extract rare-earth elements

A new method could help meet the demand for these materials in a more sustainable way

Spotted: Rare earth elements (REEs), such as terbium, lanthanum, and neodymium, are necessary components in many high-tech consumer products, including smartphones, computers, electric vehicles, TVs, electronic displays, and wind turbines. However, by 2011, REEs were in short supply, with China accounting for 97 per cent of world production.

Now, scientists at Trinity College Dublin and University College Dublin have discovered a sustainable way of extracting REEs, finding that calcium carbonate (calcite) in eggshells can be used to effectively separate REEs. The team’s insight was that, once in solution, REEs can enter the eggshells via diffusion before forming on the eggshell surface at higher temperatures. 

At 90 degrees Celsius, a rare earth compound called kozoite formed on the shells, while at 205 degrees Celsius, this mineral transitioned into bastnasite. Crucially, this latter material, which is stable, is used by the industry to extract REEs for technology applications. 

The research, which was funded by was funded by Science Foundation Ireland, Geological Survey Ireland, and the Environmental Protection Agency under the SFI Frontiers for the Future Programme, suggests that it is possible to repurpose waste eggshells as a low-cost, eco-friendly way to help meet the growing demand for REEs. The eggshells trap distinct rare earths within their structure over time, which can then be separated out for reuse.

Today, REEs are in increasing demand but relatively short supply. In addition, while REEs are vital for sustainable technologies, their mining is devastating for the environment, usually requiring the digging of vast, open pits. When poorly regulated, REE mining can produce wastewater ponds filled with acids, heavy metals and radioactive material that then leaks into groundwater. The research can be read on ACS publications’ website.

Written By: Lisa Magloff