North American Steelmaking Slags-a Source for Critical Elements

Abstract

The need for critical minerals will continue to rise as the world population continues to grow and the world strives to limit global warming. Countries determine their critical minerals lists based on the minerals and elements that are sensitive to supply chain disruptions or are in limited supply. The traditional source for critical minerals has been mineral deposits. These deposits take decades to bring into production and hundreds of millions of dollars. There is an advantage to sourcing these elements from waste due to the immediate availability of the waste and the relatively inexpensive cost to obtain it. Steelmaking slag is a waste type that is produced as steel is made. This study shows that the North American steelmaking slag analyzed contains 17 critical elements (Al, Ba, Co, Cr, Cu, Mg, Mn, Mo, Ni, P, Sb, Sc, Ti, V, W, Zn, Zr) as well as 9 of the rare earth elements (Dy, Eu, Gd, La, Lu, Pr, Tb, Y, Yb). Recovering value from steel slags is an underexplored area of research. Extraction techniques include pyrometallurgy, hydrometallurgy, and biohydrometallurgy. Biohydrometallurgy looks to be a promising extraction technique from cost and environmental perspectives. As long as steel is produced, there will be a source of steelmaking slag, which makes this type of slag waste a "renewable" resource for critical elements.

A Closer Relationship with Our Metals

“…Increasingly, however, improved technologies (including biological methods with bacteria) 20 are being used to extract metals from tailings and wastewater. As an example, waste material (slag) from steelmaking has been found to contain high concentrations of twenty-seven elements typically included in current lists of critical minerals, 21 while coal tailings and coal by-products contain significant amounts of rare-earth elements (REEs). 22 Feasible methods for recovery of metals from these waste streams are under development and could be offered as a service by specialized suppliers, working in partnership with communities, mining companies and manufacturers.…”