The rising need for red mud that contain gallium and scandium motivates the use of existing red mud as a resource

Dr Greeshma Gadikota, Professor at Columbia University, has explained in this interview the growing importance of advanced recovery technologies for extracting critical metals such as gallium and scandium from red mud. She noted new technologies that are more energy and material-efficient are needed for the recovery of critical metals from red mud because its critical feature is in its co-presence in an iron-rich mineral matrix. Already some of the leading universities in the United States have developed technologies for the separation of nickel, cobalt, and manganese from spent battery materials under the leadership of Dr Greeshma.

Dr Greeshma Gadikota is the Lenfest Earth Institute Chair and Professor in the Department of Earth and Environmental Engineering and Columbia Climate School at Columbia University. Prior to her appointment at Columbia University, she served on the faculty at Cornell University and the University of Wisconsin – Madison. Her research is focused on: (i) advancing novel technologies for the co – recovery of sustainable energy carriers and energy critical and relevant metals while valorizing multiple emission streams and (ii) developing sustainable subsurface energy technologies. This vision is realized by unlocking the underlying cross – scale fluid – surface interactions at the molecular –, nano  –,  and meso – scales to inform field scale deployment. Her scientific contributions are recognized by the DOE, NSF and ARO CAREER Awards, Sigma Xi Young Investigator Award, Cornell Engineering Research Excellence Award, Inaugural Cornell Rising Women Innovator Award, AICHE Sabic Award for Young Professionals, and ACS Women’s Chemists Committee (WCC) Rising Star Award to list a few notable recognitions.

To know more about critical metals recovery from red mud and how the industry is mastering the art, read the full interview below. 

AL Circle: The US is a 100 per cent net importer of gallium and scandium. How can advanced recovery technologies, particularly those harnessing byproducts like red mud, transform this dependency to securing a localised and sustainable supply chain for critical minerals? 

Dr Greeshma Gadikota: Red mud is produced as a result of bauxite processing for aluminum production. The “red” in red mud is a result of the high content of iron in these materials. Conventional bauxite processing is typically tuned for aluminum recovery and not gallium or rare earth element (REE) production. As a result, these critical metals remain in the red mud residue resulting from bauxite processing. The rising need for feedstocks that contain gallium and scandium motivates the use of existing feedstocks, such as red mud, as a resource. One of the unique and challenging features of red mud is that the critical metals, such as gallium and scandium, are co-present in an iron-rich mineral matrix. Conventional technologies, including the use of elevated temperature and externally sourced reagents that are consumed, add to the energy and emissions intensity of red mud processing. To address this challenge, new technologies that are more energy and material-efficient are needed for the recovery of critical metals from red mud. While primary mining capacity is built in the US, including the ability to harness REE and gallium-bearing ores in Sheep Creek, Montana, through U.S. Critical Materials (USCM), it is crucial to tap into existing secondary resources such as red mud as a resource for critical materials.

AL Circle: How much gallium, scandium and other rare earth elements do you expect to recover from red mud through the ‘Mud to Metal’ programme? How do you expect to get steady access to red mud for processing and steady mineral extraction, given that the United States domestic alumina refining operations are slowing down?

Dr Greeshma Gadikota: Reasonable estimates of gallium and scandium concentrations in red mud are 50-80 ppm and 70-120 ppm, respectively. These concentrations are based on the compositions of bauxite ores. Our goal is to successfully separate gallium, scandium, and other critical metals and produce high-purity concentrates of these metals. We are developing processes at the bench scale to achieve this objective. The experiments are to the scale of grams of materials tested. We will then harness this information to explore opportunities for scale-up. Our plan is to develop red mud valorization technologies that can be applied in the US and overseas, where aluminum processing is growing.

AL Circle: As your research also focuses on energy, how do you see the evolving role of aluminium in the energy sector in the United States and the rest of Americas? In what ways are aluminium and other critical metals reinforcing one another’s contributions to energy solutions? 

Dr Greeshma Gadikota: Secondary processing of aluminum from post-consumer scrap, such as spent cans, is rapidly growing in the US. Aluminum is an essential component of lightweight vehicles, and its non-corrosive nature makes it highly sought after for other applications. To meet this growing demand in the US and overseas, primary processing of bauxite in the US with co-recovery of gallium, scandium, and other materials in a closed-loop processing mode can greatly advance domestic manufacturing.

AL Circle: Red mud is a hazardous byproduct with high alkalinity.  What safety protocols do you plan to take to prevent spill while dealing with and processing red mud for critical minerals extraction? 

Dr Greeshma Gadikota: Red mud is always transported and contained in special containers. There are protocols on storing these materials in labs based on the recommendations of Environmental Health and Safety (EH&S) recommendations, which we adhere to.

AL Circle: Please share your projections on the demand and consumption of gallium, scandium, titanium, and rare earth elements in the United States by 2030. To what extent do you anticipate domestic production meeting these demands by the projected timeline? 

Dr Greeshma Gadikota: Gallium: Domestic gallium consumption is to the order of 20-30 tonnes per year. In contrast, red mud has 30-50 million tonnes of accumulated red mud in the US. In the Gramercy site along in Louisiana, we have ~30 million tonnes of accumulated red mud. Assuming that gallium composition is to order of 50 ppm, the Gramercy site can contain up to 1,500 tonnes of gallium. We only need to extract ~1/30th of the gallium in the Gramercy site to meet domestic gallium demand. Any gallium extracted in excess can be exported.

Scandium: US scandium consumption is roughly 7–10 tonnes per year (mostly as scandium oxide or alloy additions). Assuming that scandium concentration is to the order of 80 ppm, the Gramercy site can contain up to 2,400 tonnes of scandium. As with gallium, a small fraction is needed for domestic consumption, and the residual quantities are exported overseas.

Titanium: Titanium compositions in red mud can range from 1-10 per cent in red mud. Assuming that the Gramercy site can contain up to 2 per cent titanium oxide composition, this site can contain up to 0.6 million tonnes of this material. Red mud can meet a substantial quantity of domestic titanium dioxide demand, which is to the order of 1-1.5 million metric tons per year.

Rare Earth Elements (REEs): REEs are to the order of 400 – 2000 ppm in red mud. The recovered rare earth elements in the form of mixed oxides can be sequentially separated and re-processed for meeting domestic needs. REEs compositions vary based on the bauxite ore resource.

AL Circle: What other critical mineral extraction technologies has your group developed? What have been their success rates when deployed, and how do they compare in terms of scalability and impact? 

Dr Greeshma Gadikota: My group has developed technologies for the separation of nickel, cobalt, and manganese from spent battery materials; nickel and magnesium recovery from earth abundant silicate ores; copper recovery of sulfide ores; REEs from ores and spent materials; and aluminium and manganese recovery from dross, a byproduct of secondary aluminium processing, to list a few. The novelty in these recovery pathways is the use of electrified chemical processes with regenerable materials. This approach is designed to lower the chemical and energy intensity of these pathways compared to existing routes. The closed-loop nature of these processes promotes co-recovery of multiple co-products while limiting emissions that need to be disposed. These pathways are at Technology Readiness Levels of 2-3 or substantially higher, indicating that they have been demonstrated successfully at the lab-scale and that the next phase is integration in relevant environments.

AL Circle: Extracting gallium, scandium, and titanium without using red mud relies on alternative secondary raw materials such as coal fly ash, zinc refining residues, and titanium pigment production waste. How effectively are these materials being utilised in the United States for critical minerals extraction? Has Columbia University explored these materials in its research for minerals recovery?

Dr Greeshma Gadikota: Secondary resources are post-industrial or post-consumer materials that are typically disposed and not valorized. With high-grade ores being increasingly depleted and the reliance on the supply of critical materials from overseas waning, there is a rising appetite to valorize secondary resources for critical metal recovery. Several industrial residues, such as slags and coal fly ash, are used directly as transportation and construction materials without further chemical processing. The high demand for critical metals, the shortfall in domestic supply, slow permitting processes for primary mining, and the potential to lower the land footprint of these secondary resources motivate the use of secondary resources for critical metal extraction. My group has a long history of valorizing a wide range of secondary resources for critical material recovery, including slags from iron and steel making, dross from secondary aluminum processing, organic components of biomass for producing porous graphitic carbon, steel dust for zinc recovery, geothermal brines and produced water for lithium extraction, and nickel, cobalt, and manganese recovery from spent battery materials. This work complements our ongoing work on primary ore processing for the extraction of several critical metals, including but not limited to REEs, gallium, nickel, cobalt, copper, and platinum group metals.

Author’s image credit: David Dini/Columbia Engineering