Skip to main content
U.S. flag

An official website of the United States government

Geochemical characterization, acid neutralization potential, and phosphate removal capacity of modern and legacy iron and steel slag from the Chicago-Gary area of Illinois and Indiana, USA

May 30, 2020

Steelmaking slag from near Chicago, USA, may be a viable option for treating phosphate-rich or acidic waters. Iron and steel slags from legacy and modern operations in the Chicago-Gary area of Illinois and Indiana, USA, are predominantly composed of Ca, Fe, and Si, with generally lesser amounts of Al, Mg, and Mn. Simulated weathering tests suggest that potentially deleterious elements such as Cr and Mn, present in significant concentrations in some samples, are generally hosted in insoluble phases making use in water treatment applications possible. However, generation of high pH and alkaline solutions may be an issue. Batch and flow-through column experiments document effective removal of phosphate from synthetic solutions for nearly all slag samples, suggesting it may be a useful material in treating nutrient-rich waters. The air-cooled fine fractions (< 10 mm) of modern slag were most effective at removing phosphate; other types, including modern granulated, modern air-cooled coarse fractions (> 10 mm), and legacy slag were effective, but to a lesser degree. An additional water treatment application is the use of slag to neutralize acidic waters. Most slag samples are extremely alkaline and have high net neutralization potentials (NNP) (400 ? 830 kg CaCO3/t), with the highest approximately equivalent to 80% the neutralization potential of calcite. The phosphate removal capacity and NNP correlate positively with total Ca content and the dissolution of Ca minerals facilitates secondary Ca phosphate formation and consumes acid during hydrolysis. Utilizing locally available slag to treat waste or agricultural waters in this region may be a higher value alternative than use in construction, potentially offsetting restoration costs to degraded legacy areas and decreasing steel manufacturers? current waste footprint. This data release provides information about these iron and steel slags and includes the following: bulk chemistry, acid-base accounting, particle size analysis, synthetic precipitation leaching protocol (SPLP) results, and batch and column phosphate removal experiments. The data presented here are summarized and interpreted in the following article: Piatak, N.M., Seal, R.R. II, Hoppe, D.A., Green, C.J., and Buszka, P.M., 2019, Geochemical Characterization of Iron and Steel Slag and Its Potential to Remove Phosphate and Neutralize Acid: Minerals, v. 9, no. 8, 468.