According to a study published in ACS Omega, researchers from Trinity’s School of Natural Sciences and iCRAG, the Science Foundation Ireland research center in applied geosciences, discovered that eggshell waste could recover rare earth elements (REEs) from water, providing a new, environmentally-friendly extraction method.
Dr Remi Rateau, lead author of the study (left), and Prof. Juan Diego Rodriguez-Blanco, principal investigator. Image Credit: Trinity College Dublin
This remarkable finding has the potential to substantially influence the long-term recovery of rare earth elements (REEs), which are increasingly in demand for use in green energy technologies.
REEs, vital for technologies like electric cars and wind turbines, are in high demand but low supply. As a result, scientists must devise new techniques for extracting them from the environment, preferably sustainably, as present methods are frequently detrimental.
The researchers observed that eggshells' calcium carbonate (calcite) can efficiently absorb and extract these essential REEs from water.
Eggshells were placed in solutions containing REEs for up to three months and at varying temperatures, from a comfortable 25 °C to a blistering 205 °C. They discovered that at higher temperatures, the rare earth formed new minerals on the eggshell surface. The elements could penetrate the eggshells by diffusion along the calcite boundaries and the organic matrix.
The surface of the eggshell assisted in the recovery of kozoite formations, a rare earth compound, at 90 °C. As the temperature rose, the eggshells had a full metamorphosis, with the calcite shells disintegrating and being replaced with polycrystalline kozoite.
This material eventually changed into bastnasite, the stable rare earth carbonate mineral that the industry uses to extract REEs for technology purposes, at its highest temperature of 205 °C.
Based on this novel approach, waste eggshells can be used as an inexpensive, eco-friendly material to help fulfill the increasing demand for REES since the eggshells gradually retain different rare earth elements inside their structure.
This study presents a potential innovative use of waste material that not only offers a sustainable solution to the problem of rare earth element recovery but also aligns with the principles of circular economy and waste valorization.
Dr Remi Rateau, Study Lead Author and Research Fellow, School of Natural Sciences, Trinity College Dublin
Principal Investigator Prof. Juan Diego Rodriguez-Blanco emphasized the broader implications of the findings, adding, “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.”
The published journal study can be seen on the publisher’s website. The Science Foundation Ireland, Geological Survey Ireland, and the Environmental Protection Agency supported this research as part of the SFI Frontiers for the Future Programme.
Trinity’s Department of Geology, part of the School of Natural Sciences, undertook the study. iCRAG (Irish Center for Research in Applied Geosciences) is an SFI center dedicated to geoscience research, particularly focusing on sustainable resource management and environmental protection.
Journal Reference:
Rateau, R., et. al. (2024) Utilization of Eggshell Waste Calcite as a Sorbent for Rare Earth Element Recovery. ACS Omega. doi:10.1021/acsomega.4c00931