Eggshell waste used to capture rare earth elements

Rare earth elements (REEs) are in increasing demand across the energy transition, forming vital components in technology such as electric cars and wind turbines. As a result, new methods of harvesting REEs from the environment are welcome, particularly when the conduit is a waste material and the process has a low carbon impact.  

The researchers, from Trinity College Dublin’s School of Natural Sciences and the Irish Centre for Research in Applied Geosciences (iCRAG), proposed that the calcium carbonate (calcite) in eggshells could effectively absorb and separate valuable REEs from water.

They placed eggshells in solutions containing REEs at various temperatures from 25°C to 205°C,  for different time periods of up to three months. It was found that the elements could enter the eggshells via diffusion along the calcite boundaries and the organic matrix and, at higher temperatures, that the REEs built new minerals on the eggshell surface. The work is published in ACS Omega.