Observations of FeO Reduction in Electric Arc Furnace Slag by Aluminum Black Dross: Effect of CaO Fluxing on Slag Morpho

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ALUMINUM dross by-products of the aluminum industry are typically classified into three types based on their concentrations of metallic Al: aluminum white dross (AWD, 15-70 mass pct Al), aluminum black dross (ABD, 10-20 pct Al), and aluminum salt cake (ASC, approximately 5 pct Al).[1,2] In particular, ABD is classified as hazardous waste according to the European Waste Catalogue and the United States Environmental Protection Agency’s Hazardous Waste List (entry 100309), because ABD has the following listed properties: highly flammable (H3-A), harmful (H5), toxic (H6), leachable (H13), and ecotoxic (H14).[3] ABD reacts strongly with water, leaching out harmful and toxic gases such as NH3, CH4, PH3, and H2S.[2,4] Thus, several physicochemical studies on the characterization of ABD have been carried out, including investigations JUNG HO HEO is with the Research & Development Center, LSNikko Copper Inc., Ulsan 44997, Korea. TAE SUNG KIM is with the Department of Materials Engineering, Hanyang University, Ansan 15588, Korea. VEENA SAHAJWALLA is with the Centre for Sustainable Materials Research and Technology (SMaRT) of the School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia. JOO HYUN PARK is with the Department of Materials Engineering, Hanyang University, and also with the Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm 100 44, Sweden. Manuscript submitted December 18, 2019.

METALLURGICAL AND MATERIALS TRANSACTIONS B

of properties such as density,[5,6] porosity,[6] and toxicity[1] as well as mineralogical and structural interpretations.[7–11] Hydrolysis treatment of Al dross to convert it to a non-hazardous material has been experimentally investigated.[12] Nonetheless, ABD has been indiscriminately discarded in landfills or disposed of without appropriate treatment, thus contaminating the environment by introducing undesirable species such as F, Cl, NH4+, and CN into groundwater and toxic gases into the atmosphere.[2] Similarly, electric arc furnace (EAF) slag, which is also categorized as a hazardous waste in the steelmaking industry according to the list mentioned above (entry 100201),[3] has generally been disposed of in landfills.[13] Landfilling of EAF slag is problematic because of its environmental contamination by means of leaching, which can lead to many physical disorders and health concerns. Furthermore, the generation of huge amounts of EAF slag causes waste management difficulties, quickly filling landfill sites. Hence, it is very important to develop efficient solutions to manage ABD and EAF slag. One well-known solution is to utilize ABD and EAF slag directly as raw materials as substitutes for concrete and ceramics in the fields of building and road construction. Slags have good properties for this purpose, such as corrosion and thermal shock resistance, refractoriness, and abrasion resistance. In addition, several investigations have been made into the application of ABD as an Al2O3 source for Al2O3-containi