P. Butreddy, S. Mergelsberg, J.N. Jocz, D. Li, V. Prabhakaran, A.J. Ritchhart, C.V. Subban, J. Kellar, S.R. Beeler, S.W. Keenan, E. Nakouzi
Pacific Northwest National Laboratory,
United States
Keywords: selective precipitation, manganese, ferromanganese nodules, leaching, metal separation, critical elements
Summary:
Meeting global sustainability and climate goals requires a rapid transition to renewable energy technologies, which are heavily reliant on critical elements like manganese. Manganese plays a vital role in producing battery cathodes, consumer electronics, and steel, but geopolitical and environmental challenges often constrain its sourcing. This study investigates ferromanganese nodules from the Oacoma Site in South Dakota as a sustainable and accessible unconventional feedstock for manganese extraction. These nodules, readily available at the surface, primarily consist of rhombohedral metal carbonates, with manganese concentrations ranging from 3.5–5.4 at%. We developed an efficient pH-cycling strategy for manganese extraction based on the titration experiments and an equilibrium speciation model. Initially, selective dissolution of calcium and manganese ions was achieved in acidic conditions by dissolving the carbonate phases at pH 1.5–2. Subsequently, iron hydroxide was selectively precipitated by increasing the leachate's pH to 5.7, followed by the production of relatively pure manganese oxide at pH 10.9. This method achieved manganese recoveries >65% with purities >70at% relative to other metals, without needing specialty chemicals or generating highly acidic waste. A preliminary scalability assessment underscores the industrial viability of this environmentally friendly extraction process, highlighting its potential to provide a sustainable manganese supply.