November 22, 2022

Combining Carbon Dioxide Capture with Rare Earth Element Recovery

Newly funded work will explore the behavior of rare earth element-containing molecules to enable red mud waste re-mining

Photograph of red mud waste, a byproduct of aluminum production

Red mud waste contains important, and challenging to separate, rare earth elements.

A project led by Pacific Northwest National Laboratory (PNNL) scientist Xin Zhang has been selected to receive $1,000,000 in funding from the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E). The funding is part of the ARPA-E Mining Innovations for Negative Emissions Resource Recovery (MINER) program, which aims to develop market-ready technologies that will increase domestic supplies of critical elements required for the clean energy transition.

The PNNL project is titled “Re-Mining Red Mud Waste for CO2 Capture and Storage and Critical Element Recovery (RMCCS-CER).” Red mud is a common waste product from aluminum production that contains rare earth elements (REEs) important for advanced technological and energy applications. As REEs naturally occur together, isolating them presents a major scientific challenge.

The team will combine advanced in situ and ex situ techniques to determine the solubility and thermodynamic features of REE minerals. Importantly, these minerals include carbonates produced by reacting carbon dioxide with the REEs. They will then feed this information into new databases of REE mineral characteristics. Once the databases are developed, the team will use a machine learning based approach to identify conditions suited for optimized REE recovery.

“We’re very excited about this project,” said Zhang. “The REE characteristics database will be an extremely useful resource for researchers and industry working with REEs. Recovery, separation and purification are incredibly important for generating usable REEs.”

The project team includes two partner institutions, Arizona State University and Washington State University. Researchers working in close collaboration will focus on generating new experimental data and examining the literature to build REE solubility and thermodynamic databases.

This will lay fundamental groundwork for the ultimate goal of developing carbon negative re-mining technologies that use captured carbon dioxide to create stable carbonate minerals. As REEs are currently isolated through a highly toxic acid leaching process, the approach proposed in this project represents a substantial environmental improvement.  

Published: November 22, 2022