Formation of Mill Scale in Portland Cement Production and Its Processing into Coagulants
DOI:
https://doi.org/10.51699/8psy8v47Keywords:
mill scale; Portland cement; iron coagulants; ferric chloride; polyferric sulfate; acid leaching; wastewater treatment; circular economyAbstract
Mill scale, a by-product of steel hot rolling operations, represents a significant iron-rich waste stream with considerable potential for valorization. While traditionally utilized as a raw material in Portland cement clinker production, recent advances have demonstrated the feasibility of converting mill scale into valuable iron-based coagulants for water and wastewater treatment. This review examines the formation mechanisms of mill scale during steel production, its current utilization in cement manufacturing, and innovative pathways for processing mill scale into ferric chloride, ferric sulfate, and polyferric sulfate coagulants. The synthesis methods, characterization techniques, and application performance of these recovered coagulants are systematically analyzed. Comparative assessment reveals that mill scale-derived coagulants exhibit treatment efficiencies comparable to commercial products while offering significant economic and environmental advantages. This review provides a comprehensive framework for transitioning from linear disposal practices to circular economy approaches in heavy industry waste management.
References
[1] Madias J. The recycling of steel mill by-products. Ironmaking & Steelmaking. 2023;50(4):345-356.
[2] AEIFOROS Metal Processing S.A. Mill scale as raw material for cement manufacturing. Available at: https://www.aeiforos.gr/en/mill_scale
[3] Zeng H, Li S, Sun X, Liu C, Zhang J, Li D. Preparation and characterization of polyferric sulfate derived from iron sludge in de-ironing water plants and its utilization in water treatment. Water. 2025;17(17):2632. https://doi.org/10.3390/w17172632
[4] Solmaz A, Bölükbaşi ÖS, Sari ZA. Green industry work: production of FeCl3 from iron and steel industry waste (mill scale) and its use in wastewater treatment. Environmental Science and Pollution Research. 2024;31(13):19795-19814. https://doi.org/10.1007/s11356-024-32451-6
[5] Montanstahl. Hot rolling process: advantages, defects and what to know. Available at: https://www.montanstahl.com/blog/hot-rolling-steel-stainless-profiles/
[6] El-Hussiny NA, Shalabi MEH. Conversion of mill scale waste into valuable products via carbothermic reduction. Journal of Metallurgy. 2015;2015:926028. https://doi.org/10.1155/2015/926028
[7] Waste Optima. Mill scale recycling: from steel waste to valuable resource. 2025. Available at: https://www.wasteoptima.com/blog/mill-scale-recycling
[8] BricknBolt. Mill scale - uses, benefits & recycling in industry. 2025. Available at: https://www.bricknbolt.com/blogs-and-articles/construction-guide/mill-scale
[9] US Patent 6709510B1. Process for using mill scale in cement clinker production. 2002.
[10] Understanding Cement. The cement kiln. Available at: https://www.understanding-cement.com/kiln.html
[11] Li Y, et al. Mill scale as an industrial solid waste for preparing iron nanoparticles. Nano Bio Letters. 2022;12:038.
[12] Zeng H, et al. Preparation and characterization of polyferric sulfate derived from iron sludge. Water. 2025;17(17):2632.
[13] Production of a ferric chloride coagulant by leaching an iron ore tailing. Minerals Engineering. 2020;154:106456.
[14] De Gruyter. Poly-ferric sulphate as superior coagulant: a review. Reviews on Advanced Materials Science. 2022;61(1):220327.
[15] Polymersco. Coagulation/flocculation jar test procedure. Available at: https://polymersco.com/coagulation-flocculation-jar-test-procedure/
[16] Ottink T. Recycling of steel grinding swarf via production of iron chloride coagulants for water treatment. PhD Thesis. Chalmers University of Technology, 2022.
[17] Ellen MacArthur Foundation. Material circularity indicator. 2023.
[18] Sverguzova SV, et al. Electric steelmaking dust as a raw material for coagulant production. Journal of Mining Institute. 2023;260:279-288.
[19] Mill Scale.org. Mill scale for cement use. Available at: https://millscale.org/mill-scale-for-cement-use/
[20] Mahlohla B, et al. Synthesis of poly-alumino-ferric sulphate coagulant from acid mine drainage by precipitation. Metals. 2019;9(11):1166.
[21] Zubkova OS, et al. Research of combined use of carbon and aluminum compounds for wastewater treatment. Russian Journal of Chemistry and Chemical Technology. 2020;63(4):86-91.
[22] AGICO Cement. Cement rotary kiln. Available at: https://cementplantequipment.com/products/rotary-kiln/
