Selectively Recovering Manganese from Surface Accessible Nodules

The Science

Manganese is a critical element for industrial applications, such as steel production and energy technologies. The United States currently relies on imported manganese, making domestic production of the pure material important for developing a robust supply chain. Researchers from the Non-Equilibrium Transport Driven Separations (NETS) Initiative and the South Dakota School of Mines and Technology developed a new process to extract manganese from surface nodules sourced from the Oacoma site in South Dakota. They used pH cycling, alternating acidic and basic conditions, to selectively dissolve and precipitate manganese. The process involves no specialty chemicals and minimizes hazardous waste and carbon dioxide production.

The Impact

Manganese is essential to making steel and plays a central role in materials for emerging energy technologies. Finding scalable processes to isolate manganese from available domestic sources, such as surface nodules, can help develop a stable source of manganese to meet industrial and national security needs. Surface nodules represent an exciting new source of critical minerals, and their accessible location results in fewer disturbances and less required infrastructure than traditional or “deep-sea mining” sources. The NETS-developed process involves fewer steps than commercial separations used for ocean nodules in industrial deep-sea mining and creates less hazardous waste, reducing the overall cost of manganese extraction.

Summary

New energy technologies are central to meeting domestic economic development and national security goals. However, these technologies require critical elements that can be challenging to source. NETS researchers focused on ferromanganese nodules found in South Dakota as a potential source of manganese. The Oacoma site has nodule deposits containing an estimated five billion metric tons of manganese, with many nodules directly exposed and accessible at the surface. Previously, these nodules were considered ores of too low a grade to be economically viable for mining. But new processes for isolating manganese, such as the pH cycling approach developed by the NETS team, may make nodules a viable feedstock. To demonstrate the pH cycling approach, researchers dissolved nodules in acid and selectively precipitated out manganese oxide at basic conditions. The process required no specialty chemicals because diluted solutions of cheap and readily available commercial concentrated hydrochloric acid, nitric acid, and sodium hydroxide enabled the necessary pH changes. The overall approach isolated over 65 percent of the manganese at over 70 percent purity in a single cycle without the use of any specialty chemicals. The process has the potential to be scaled for domestic manganese production.

Contact

Elias Nakouzi, Pacific Northwest National Laboratory, elias.nakouzi@pnnl.gov

Funding

This study was supported by a collaborative effort funded by the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory under the NETS Initiative. Additional funding for sample acquisition and shipping was provided to the South Dakota School of Mines and Technology by the Department of Geology and Geological Engineering.