Rare earth elements (REES) are essential ingredients for electronics and materials that will power renewable infrastructure for the energy transition. In an interesting development, Irish scientists have discovered that Eggshell waste can recover valuable REE from water.
This could simply be the precursor to a new and more ecological way of extraction, especially compared to the intensive mining processes currently required to extract them from geological layers. In industry, separating and extracting these minerals that are finely distributed in rocks is usually a complex technological process.
Testing execution
In a collaboration between professionals from iCRAG, Science Foundation Ireland and the Faculty of Natural Sciences at Trinity College Dublin, the team published their findings in ACS Omega. In their article it is explained that the use of calcium carbonate (calcite) present in the shells of Eggs can absorb and separate REEs of water successfully.
Based in the Department of Geology at Trinity College Dublin, The team placed eggshells in liquid solutions that had REEs present but at different temperatures; from 25 °C up to 205°C. The team also tested different time periods, up to three months.
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As a result, they discovered that elements could enter the eggshells by diffusion along the boundaries of the calcite and the organic matrix. At higher temperatures, REEs solidified new minerals on eggshell surfaces.
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At 90°C, the eggshell helped recover a rare earth compound known as kozoite. As temperatures rose, the eggshell transformed with calcites that dissolved and were replaced by kozoite in crystalline form.
At the maximum temperature, the mineral converted to bastnasite a sought-after rare earth carbonate used to extract REEs for technological applications in industry.
We can see that Eggshells can “trap” important rare earths over time and at different temperatures . This raises questions about eggshell residue and whether these calcite-hosting materials could have more use than initially thought.
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Lead researcher Prof. Juan Diego Rodríguez-Blanco added: “By transforming eggshell waste into a valuable resource for rare earth recovery, we address critical environmental concerns associated with traditional extraction methods and contribute to the development of greener technologies”.
Throw away eggshells may not be a good idea, as this study shows its value as a potentially ecological way to harvest more REE that will be in demand with the growing energy transition.
News source:
A big discovery: waste eggshells can recover rare earth elements needed for green energy. Trinity College Dublin. ACS Omega. DOI: 10.1021/acsomega.4c00931
