Discarded oyster shells can capture and remove rare earth elements from polluted water, according to new research by a team at Trinity College Dublin (TCD).
The research, which has been published in the journal Science of the Total Environment, shows that waste seashells, especially oyster shells, have a natural ability to turn rare earth elements into stable mineral crystals.
As the team explains, rare earth elements are essential components of modern technologies, from wind turbines and electric vehicles to smartphones.
However, their extraction and processing creates environmental risks when these metals leak into water systems, they say.
They are also at the centre of growing geopolitical tensions, as global supply is heavily concentrated in a few countries and demand for these strategic materials continues to increase, the team notes.
If released into rivers or lakes, rare earth elements can accumulate in aquatic ecosystems and disrupt microorganisms, plants, and animals, the team explains.
In laboratory experiments, the team says it exposed crushed shells (mussels, cockles and oysters) to solutions containing rare earth elements.
Shell Science Breakthrough: Dr Rémi Rateau (left) and Prof Juan Diego Rodriguez-Blanco of Trinity College Dublin led research showing oyster shells can trap rare earth elements
The chemical reaction triggered is such that the minerals in the shell dissolve and are replaced by new minerals containing the rare earth elements.
In effect, the shells act as a “template” that converts dissolved metals into solid mineral crystals that remain locked inside the shell material, the team explains.
Oyster shells performed “particularly well”, as their natural microstructure allows the chemical reaction to continue deeper into the shell, capturing significantly more rare earth elements than other shells, the team says.
“The results suggest that shell waste could potentially be used as a low-cost and environmentally friendly material to help treat contaminated water – or even to recover valuable metals from industrial streams,” it states.
Dr Rémi Rateau from TCD’s School of Natural Sciences, who is first author of the study, says that “among the most exciting elements of the discovery is that relatively small amounts of shell waste could remove substantial quantities of rare earth metals from contaminated water, meaning a genuine, tangible impact could be created with as little as a few kilograms of oyster shells.”
“Every year, the global aquaculture industry generates millions of tonnes of shell waste, much of which is discarded or sent to landfill, so repurposing this waste could instead offer both an environmental clean-up tool and a sustainable recycling pathway,” he says.
Shell Power Concept: Illustration of how waste seashells can recover rare earth elements from water, highlighting potential for sustainable recycling and clean energy materials. Photo: Prof Juan Diego Rodriguez-Blanco
Dr Juan Diego Rodriguez-Blanco, also from TCD’s School of Natural Sciences, and principal investigator of the project, added that “what makes this discovery particularly promising is that the process is entirely mineral-driven”.
“The shells naturally transform dissolved rare earth elements into new solid minerals, so this isn’t a process that is difficult to drive, or one that requires much financial outlay or technical equipment.”
“By understanding how these reactions work, we can start designing low-cost and environmentally friendly strategies to remove critical metals from contaminated waters while also giving new value to a major waste product,”he says.
The research was conducted at TCD’s Department of Geology at the School of Natural Sciences.
The iCRAG (Irish Centre for Research in Applied Geosciences)laboratory at TCD was part-funded through a Research Ireland grant.
The Geological Survey Ireland, the Environmental Protection Agency, and a Provost PhD Award from TCD, also supported the research.
The published journal article can be read here
