An innovative study proposes leveraging Chilean steel slag to extract critical minerals such as Cobalt and Manganese from ferromanganese crusts, key elements for the development of clean energy technologies that support a just and inclusive global energy transition.

In a context of growing global demand for critical minerals such as cobalt (Co) and manganese (Mn), essential for the energy transition, researchers are seeking ways to recover minerals from the seabed. The proposal reuses steel slag from the Chilean iron and steel industry as a reducing agent for the acid-reductive leaching of ferromanganese crusts rich in Co and Mn, found at depths between 400 and 7,000 meters below sea level. The mineral processing proposed by these researchers achieves a recovery of up to 80% of Co and 40% of Mn, reducing waste generation and the environmental footprint of traditional extraction of these metals, respectively.

SERC Chile – University of Antofagasta researcher, Dr. Felipe M. Gallegillos Madrid, explained that “the reuse of copper or steel slag provides significant advantages over conventional reducing agents. These slags contain iron oxides, silica, and metallic traces with electrocatalytic and reducing properties, transforming an abundant waste into a useful input. This helps reduce dependence on expensive or critical materials (such as noble metals or rare earths) and, at the same time, promotes the circular economy, transforming an environmental liability into a valuable resource.”

The team used optimization tools such as Response Surface Methodology (RSM) and Design of Experiments (DOE), which allowed for the adjustment of parameters such as leaching time, pH, temperature, and the crust/Fe ratio to maximize efficiency and minimize the use of chemical reagents.

Reducing environmental impact with reusable slag

The SERC Chile researcher indicated that by carrying out this proposal, the environmental impact is significantly reduced, mainly because it “avoids new mining extractions, reusing millions of tons of slag accumulated each year in countries like Chile (4.5 Mt of copper slag alone per year).” In addition, it minimizes the creation of slag heaps like those abandoned in the Atacama Desert. This strategy not only mitigates the environmental pressure of terrestrial mining, but also offers a way to substantially reduce historical environmental liabilities (scattered slag heaps in northern Chile).”

This could position Chile as a “world leader in the energy circular economy of iron or copper slag, envisioning a business line never seen before.” Since the country has an extensive coastline (6,435 km) with high solar potential and direct access to seawater.

“The combination of industrial mining waste with oceanic resources positions Chile as a natural laboratory for sustainable subsea mining technologies, where slag can be used in metal recovery processes to meet the growing demand for critical metals for the manufacture of electrodes used in solar hydrogen production and energy storage without the need to exploit new deposits,” added researcher Dr. Felipe M. Gallegillos Madrid.

Finally, he maintained that the research is a contribution to advancing the sustainable energy transition, as raw material sources must be diversified: “Co and Mn are among the critical raw materials for the energy transition, and pressure on terrestrial deposits, together with geopolitical tensions, requires diversifying extraction sources. Deep-sea Fe–Mn crusts emerge as a strategic alternative for the energy transition in the face of a 100% electrified future.”